Measure Guideline:

Three High Performance 

Mineral Fiber Insulation 

Board Retrofit Solutions

K. Neuhauser

Building Science Corporation

January 2015
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iii

Measure Guideline:

Three High Performance Mineral Fiber Retrofit Solutions

Prepared for: 

The National Renewable Energy Laboratory 

On behalf of the U.S. Department of Energy’s Building America Program 

Office of Energy Efficiency and Renewable Energy 

15013 Denver West Parkway 

Golden, CO 80401 

NREL Contract No. DE-AC36-08GO28308 

Prepared by: 

Ken Neuhauser

Building Science Corporation 

3 Lan Drive, Suite 102 

Westford, MA 01886 

NREL Technical Monitor: Stacey Rothgeb 

Prepared under Subcontract No. KNDJ-0-40337-05 

January 2015 
iv

The work presented in this report does not represent 

performance of any product relative to regulated 

minimum efficiency requirements.

The laboratory and/or field sites used for this work are 

not certified rating test facilities. The conditions and 

methods under which products were characterized for 

this work differ from standard rating conditions, as 

described.

Because the methods and conditions differ, the reported 

results are not comparable to rated product performance 

and should only be used to estimate performance under 

the measured conditions.
v 

Contents

List of Figures ........................................................................................................................................... vii

List of Tables .............................................................................................................................................. ix

Definitions.................................................................................................................................................... x

Executive Summary................................................................................................................................... xi

Progression Summary: High Performance Mineral Fiber Roof Retrofit............................................. xii

Progression Summary: High Performance Mineral Fiber Wall Retrofit ............................................ xiii

Progression Summary: High Performance Mineral Fiber Foundation Wall Retrofit........................ xiv

Introduction ................................................................................................................................................. 1

1 Assess the Home.................................................................................................................................. 3

1.1 Risk Identification ................................................................................................................3

1.1.1 Identify Site Risks ....................................................................................................3

1.1.2 Identify Work Risks .................................................................................................5

1.2 Assess the Home To Determine Suitability of Options and the Need for Additional 

Control Measures .................................................................................................................6

1.2.1 Roof Measure ...........................................................................................................6

1.2.2 Foundation Measure.................................................................................................6

2 Decision-Making Criteria ..................................................................................................................... 7

2.1 Cost and Performance ..........................................................................................................7

2.1.1 Roof Retrofit ............................................................................................................7

2.1.2 Wall Retrofit ............................................................................................................8

2.1.3 Translating the Cost of Foam Plastic Insulation Board to Mineral Fiber

Insulation Board .......................................................................................................9

2.2 Fire Code Issues .................................................................................................................11

2.3 Moisture Performance ........................................................................................................11

2.4 Cladding Attachment .........................................................................................................13

2.5 Other Material Characteristics or Criteria ..........................................................................14

2.6 Trade Resources .................................................................................................................14

3 Technical Description ........................................................................................................................ 15

3.1 High Performance Mineral Fiber Retrofit Assemblies ......................................................15

3.1.1 Mineral Fiber Retrofit Roof Assembly ..................................................................15

3.1.2 Mineral Fiber Retrofit Wall Assembly ..................................................................15

3.2 Material Properties and Criteria for Mineral Fiber Insulation Board ................................20

3.3 System Interaction .............................................................................................................20

3.3.1 Water Control.........................................................................................................20

3.3.2 Air Control .............................................................................................................22

3.3.3 Vapor Control ........................................................................................................23

3.3.4 Thermal Control .....................................................................................................27

3.4 Climate Considerations ......................................................................................................28

4 Measure Implementation ................................................................................................................... 29

4.1 High Performance Mineral Fiber Retrofit Roof Assembly................................................29

4.1.1 Scope of Work .......................................................................................................29

4.1.2 Climate-Specific Factors ........................................................................................29

4.1.3 Field Inspection ......................................................................................................29

4.1.4 Implementation Risks ............................................................................................30

4.1.5 Installation Procedure ............................................................................................30
vi 

4.1.6 High Performance Mineral Fiber Retrofit Details .................................................34

4.2 High Performance Mineral Fiber Retrofit Wall Assembly ................................................41

4.2.1 Scope of Work .......................................................................................................41

4.2.2 Climate-Specific Factors ........................................................................................42

4.2.3 Field Inspection ......................................................................................................42

4.2.4 Implementation Risks ............................................................................................43

4.2.5 Installation Procedure ............................................................................................43

4.2.6 High Performance Mineral Fiber Retrofit Details .................................................45

4.3 High Performance Mineral Fiber Retrofit Foundation Wall Assembly .............................94

4.3.1 Scope of Work .......................................................................................................94

4.3.2 Climate-Specific Factors ........................................................................................94

4.3.3 Field Inspection ......................................................................................................95

4.3.4 Implementation Risks ............................................................................................96

4.3.5 Installation Procedure ............................................................................................96

4.3.6 High Performance Mineral Fiber Retrofit Details .................................................99

References............................................................................................................................................... 102
vii 

List of Figures

Figure 1. Mineral fiber retrofit roof assembly......................................................................................... 16

Figure 2. Mineral fiber retrofit roof assembly with a vented roof cladding......................................... 17

Figure 3. Mineral fiber retrofit wall assembly......................................................................................... 18

Figure 4. Insulated ground roof included with mineral fiber retrofit foundation wall approach ...... 19

Figure 5. Ratio of exterior to total insulation to control condensation of interior water vapor........ 26

Figure 6. Taped wood panel roof sheathing as air control membrane ............................................... 31

Figure 7. “Chainsaw” transition of air and water control membrane.................................................. 32

Figure 8. “Chainsaw” transition of air and water control membrane at rake ..................................... 32

Figure 9. Pre-assembled insulated roof overhang framing being lifted into place at a gable rake

for a “chainsaw” retrofit .................................................................................................................... 33

Figure 10. Schematic detail for “chainsaw” eave transition from a high performance mineral

fiber retrofit roof assembly to a high performance mineral fiber retrofit wall assembly............ 34

Figure 11. Schematic detail for non-“chainsaw” eave transition from a high performance

mineral fiber retrofit roof assembly to a high performance mineral fiber retrofit wall assembly35

Figure 12. Schematic detail for “chainsaw” gable rake transition from a high performance mineral 

fiber retrofit roof assembly to a high performance mineral fiber retrofit wall assembly............ 36

Figure 13. Schematic detail for “chainsaw” eave transition from a high performance mineral

fiber retrofit roof assembly to a non-retrofit wall assembly .......................................................... 37

Figure 14. Schematic detail for non-“chainsaw” eave transition from a high performance

mineral fiber retrofit roof assembly to a non-retrofit wall assembly............................................. 38

Figure 15. Schematic detail for “chainsaw” gable rake transition from a high performance

mineral fiber retrofit roof assembly to a non-retrofit wall assembly............................................. 39

Figure 16. Schematic detail for transition from a lower high performance mineral fiber retrofit

roof assembly to a high performance mineral fiber retrofit wall assembly ................................. 40

Figure 17. Schematic detail for transition from a lower high performance mineral fiber retrofit

roof assembly to a non-retrofit wall assembly................................................................................ 41

Figure 18. Schematic detail for “chainsaw” eave transition from a high performance mineral

fiber retrofit roof assembly to a high performance mineral fiber retrofit wall assembly............ 45

Figure 19. Schematic detail for non-“chainsaw” eave transition from a high performance

mineral fiber retrofit roof assembly to a high performance mineral fiber retrofit

wall assembly...................................................................................................................................... 46

Figure 20. Schematic detail for “chainsaw” gable rake transition from a high performance mineral 

fiber retrofit roof assembly to a high performance mineral fiber retrofit wall assembly............ 47

Figure 21. Schematic detail for eave transition from a high performance mineral fiber retrofit wall 

assembly to a non-retrofit roof assembly........................................................................................ 48

Figure 22. Schematic detail for gable/rake transition from a high performance mineral fiber

retrofit wall assembly to a non-retrofit roof assembly ................................................................... 49

Figure 23. Schematic detail for transition from a lower high performance mineral fiber retrofit

roof assembly to a high performance mineral fiber retrofit wall assembly ................................. 50

Figure 24. Schematic detail for transition from a high performance mineral fiber retrofit wall 

assembly to an insulated lower roof assembly............................................................................... 51

Figure 25. Schematic detail for transition from a high performance mineral fiber retrofit wall 

assembly to an existing lower attic .................................................................................................. 52

Figure 26. Schematic detail for transition from a high performance mineral fiber retrofit wall 

assembly to a porch roof................................................................................................................... 53

Figure 27. Schematic detail for transition from a high performance mineral fiber retrofit wall 

assembly to an attached deck in a field of wall............................................................................... 54

Figure 28. Schematic detail for transition from a high performance mineral fiber retrofit wall 

assembly to an attached deck at base of wall................................................................................. 55

Figure 29. Schematic detail for transition from a high performance mineral fiber retrofit wall 

assembly to a top of high performance mineral fiber retrofit foundation wall assembly........... 56
viii

Figure 30. Schematic detail for transition from a high performance mineral fiber retrofit wall 

assembly to a flat-surface foundation wall without exterior retrofit............................................. 57

Figure 31. Schematic detail for transition from a high performance mineral fiber retrofit wall 

assembly to a bumpy-surface foundation wall ............................................................................... 58

Figure 32. Schematic detail for window head of new window or reinstalled window in a high 

performance mineral fiber retrofit wall assembly ........................................................................... 59

Figure 33. Schematic detail for window jamb of new window or reinstalled window in a high 

performance mineral fiber retrofit wall assembly ........................................................................... 60

Figure 34. Schematic detail for window sill of new window or reinstalled window in a high 

performance mineral fiber retrofit wall assembly ........................................................................... 61

Figure 35. Steps 1 and 2 of installation sequence for new window or reinstalled window in a

high performance mineral fiber retrofit wall assembly .................................................................. 62

Figure 36. Steps 3 and 4 of installation sequence for new window or reinstalled window in a

high performance mineral fiber retrofit wall assembly .................................................................. 63

Figure 37. Steps 5 and 6 of installation sequence for new window or reinstalled window in a

high performance mineral fiber retrofit wall assembly .................................................................. 64

Figure 38. Steps 7 and 8 of installation sequence for new window or reinstalled window in a

high performance mineral fiber retrofit wall assembly .................................................................. 65

Figure 39. Steps 9 and 10 of installation sequence for new window or reinstalled window in a 

high performance mineral fiber retrofit wall assembly .................................................................. 66

Figure 40. Steps 1 and 2 of exterior trim installation sequence for window in a high

performance mineral fiber retrofit wall assembly ........................................................................... 67

Figure 41. Steps 3 and 4 of exterior trim installation sequence for window in a high

performance mineral fiber retrofit wall assembly ........................................................................... 68

Figure 42. Steps 5 and 6 of exterior trim installation sequence for window in a high

performance mineral fiber retrofit wall assembly ........................................................................... 69

Figure 43. Step 7 of exterior trim installation sequence for window in a high performance

mineral fiber retrofit wall assembly .................................................................................................. 70

Figure 44. Schematic detail for window head of an existing window remaining in place in a

high performance mineral fiber retrofit wall assembly .................................................................. 71

Figure 45. Schematic detail for window jamb of an existing window remaining in place in a

high performance mineral fiber retrofit wall assembly .................................................................. 72

Figure 46. Schematic detail for window sill of an existing window remaining in place in a

high performance mineral fiber retrofit wall assembly .................................................................. 73

Figure 47. Schematic detail for door head of new door or reinstalled door in a high

performance mineral fiber retrofit wall assembly ........................................................................... 74

Figure 48. Schematic detail for door jamb of new door or reinstalled door in a high

performance mineral fiber retrofit wall assembly ........................................................................... 75

Figure 49. Schematic detail for door sill of new door or reinstalled door in a high

performance mineral fiber retrofit wall assembly ........................................................................... 76

Figure 50. Steps 1 and 2 of installation sequence for new door or reinstalled door in a high 

performance mineral fiber retrofit wall assembly ........................................................................... 77

Figure 51. Steps 3 and 4 of installation sequence for new door or reinstalled door in a high 

performance mineral fiber retrofit wall assembly ........................................................................... 78

Figure 52. Steps 5 and 6 of installation sequence for new door or reinstalled door in a high 

performance mineral fiber retrofit wall assembly ........................................................................... 79

Figure 53. Steps 7 and 8 of installation sequence for new door or reinstalled door in a high 

performance mineral fiber retrofit wall assembly ........................................................................... 80

Figure 54. Steps 9 and 10 of installation sequence for new door or reinstalled door in a high 

performance mineral fiber retrofit wall assembly ........................................................................... 81

Figure 55. Steps 11 and 12 of installation sequence for new door or reinstalled door in a high 

performance mineral fiber retrofit wall assembly ........................................................................... 82

Figure 56. Steps 1 and 2 of exterior trim installation sequence for door in a high performance 

mineral fiber retrofit wall assembly .................................................................................................. 83
ix

Figure 57. Steps 3 and 4 of exterior trim installation sequence for door in a high performance 

mineral fiber retrofit wall assembly .................................................................................................. 84

Figure 58. Steps 5 and 6 of exterior trim installation sequence for door in a high performance 

mineral fiber retrofit wall assembly .................................................................................................. 85

Figure 59. Step 7 of exterior trim installation sequence for door in a high performance mineral 

fiber retrofit wall assembly................................................................................................................ 86

Figure 60. Schematic plan (above) and section (below) details for wire penetration and fixture 

mount in a high performance mineral fiber retrofit wall assembly ............................................... 87

Figure 61. Schematic plan and section details for wire penetration and exterior outlet box

mount in a high performance mineral fiber retrofit wall assembly ............................................... 88

Figure 62. Schematic plan and section details for duct penetration and vent hood trim mount 

in a high performance mineral fiber retrofit wall assembly ........................................................... 89

Figure 63. Steps 1 and 2 of sequence for treatment of duct/pipe penetration through a high 

performance mineral fiber retrofit wall assembly ........................................................................... 90

Figure 64. Steps 3 and 4 of sequence for treatment of duct/pipe penetration through a high 

performance mineral fiber retrofit wall assembly ........................................................................... 91

Figure 65. Steps 5 and 6 of sequence for treatment of duct/pipe penetration through a high 

performance mineral fiber retrofit wall assembly ........................................................................... 92

Figure 66. Steps 7 and 8 of sequence for treatment of duct/pipe penetration through a high 

performance mineral fiber retrofit wall assembly ........................................................................... 93

Figure 67. Step 9 of sequence for treatment of duct/pipe penetration through a high

performance mineral fiber retrofit wall assembly ........................................................................... 94

Figure 68. Schematic detail for insulated ground roof/foundation skirt with a high

performance mineral fiber retrofit foundation wall assembly ....................................................... 99

A 69. Schematic detail for transition from a high performance mineral fiber retrofit wall

assembly to a top of high performance mineral fiber retrofit foundation wall assembly

showing how the metal closure/transition flashing is secured and sealed to the

foundation wall. ................................................................................................................................ 100

Figure 70. Schematic detail for transition from a non-retrofit wall assembly to a top of high 

performance mineral fiber retrofit foundation wall assembly showing how the metal 

closure/transition flashing is secured and sealed to the foundation wall. ................................ 101

Unless otherwise noted, all figures were created by BSC.

List of Tables

Table 1. Recommended Minimum R-Value for High R-Value Enclosures............................................. 1

Table 2. NREMD Unit Costs for Insulation Board and Cavity Insulation Roof Retrofit ($/ft2) ............. 7

Table 3. National Residential Efficiency Measures Database Unit Costs for Insulation Board Wall 

Retrofit ($/ft2

) ......................................................................................................................................... 8

Table 4. Estimates of Insulation Board Costs.......................................................................................... 9

Table 5. Board-Foot Material Costs for Various Insulation Board Materials From a Single Supplier 

and the Resulting Cost per Unit Area R-Value ($/ft2

-R) .................................................................... 9

Table 6. Weight per Unit Area R-10 Insulation for Various Insulation Board Materials (lb/ft2) ......... 10

Table 7. Material Properties and Criteria for Mineral Fiber Insulation Board ..................................... 20

Table 8. Ratio of Exterior Insulation to Total Assembly Insulation for Air Leakage Condensation 

Control at 68°F Indoor Temperature................................................................................................. 24

Unless otherwise noted, all tables were created by BSC.
x 

Definitions

bf Board foot or board feet, used to refer to a volume of material 

12 in. × 12 in. × 1 in. or 144 in.3

DER Deep Energy Retrofit

ft2 Square Foot

IBC International Building Code

IECC International Energy Conservation Code

IRC International Residential Code

NREMD National Residential Efficiency Measures Database

OSB Oriented Strand Board

PIC Polyisocyanurate

SPF Spray-Applied Polyurethane Foam

XPS Extruded Polystyrene
xi 

Executive Summary

This Measure Guideline describes a high performance enclosure retrofit package that uses 

mineral fiber insulating sheathing. The Measure Guideline describes retrofit assembly and details 

for wood frame roof and walls and for cast concrete foundations. 

This Measure Guideline is intended to serve contractors and designers seeking guidance for nonfoam exterior insulation retrofit and is best suited to contractors who are either familiar with 

exterior insulation and flashing installation or who can learn these techniques.

Exterior insulation retrofit is important to the goal of net zero energy ready homes. Mineral fiber 

insulating sheathing can provide enhanced moisture durability for the exterior enclosure. Mineral 

fiber also represents a viable solution for high performance home builders, designers, and clients 

who wish to use an alternative to foam plastic insulation. 
xii 

Progression Summary: 

High Performance Mineral Fiber Roof Retrofit

INSPECT AND 

ASSESS THE 

HOME

Inspect and Assess the Home: Identify and address risks to occupants or to the building 

that could be aggravated by the work. Verify safe working conditions. Determine whether 

the building has more urgent problems that must be addressed.

REMOVE CLADDING

Remove Roof Cladding. Remove roofing to expose the roof sheathing and 

prepare the roof sheathing for the air and water control membrane.

AIR AND WATER 

CONTROL 

MEMBRANE

Install Air and Water Control Membrane. Air and water control membrane must 

also provide the necessary vapor retarder performance. Install the air and water 

control membrane continuously across the roof sheathing surface and connect it in 

an airtight and durable manner with the air control layer of adjacent assemblies. 

Seal all penetrations against air and water leaks.

MINERAL FIBER 

INSULATION 

BOARD

Install Insulation Board. Install over the air and water control membrane. Butt 

joints tight. When installing multiple layers, offset seams in two directions.

ROOF SHEATHING

Install Roof Sheathing. Install roof sheathing to serve as a nailbase for roof 

cladding (e.g., shingles). Attach sheathing to roof structure through insulating 

sheathing. For a vented roof, attach roof sheathing to purlins.

Do Not Proceed If:

• The house is not structurally sound. 

• The house includes atmospherically vented combustion appliances (except cooking 

appliances). 

• The house has knob-and-tube wiring in cavities that will be insulated. 

• The house contains hazardous materials that pose a risk to occupants or workers. 

• The house has active water leaks that will not be resolved by the retrofit projects. 

• Kitchen and/or bath fans are not vented to the exterior. 

• The home is not equipped with a whole-house ventilation system. ! • The existing roof and/or insulation materials exhibit rot, insect damage, or contamination.

Optional Step: “Chainsaw” Retrofit. If roof framing allows, remove roof sheathing, rafter tails, and 

gable rake framing to be flush with the exterior wall sheathing. Provide infill as needed to allow wall 

sheathing plane to meet roof sheathing plane.

Optional Step: “Chainsaw” Retrofit. Install framing for new roof overhangs over 

continuous insulation board.

Optional Step: Vented Roof. For vented roof, install 2 × 4 on the flat purlins over insulation 

board and fastened through insulation sheathing to roof structure.

Install Underlayment, Flashing, and Roofing. Install underlayment, ice 

and water membrane, flashings, and roofing as per new construction best ROOF CLADDING practices. AND FLASHING

5

1

2

3

4
xiii

Progression Summary: 

High Performance Mineral Fiber Wall Retrofit

INSPECT AND 

ASSESS THE 

HOME

Inspect and Assess the Home: Identify and address risks to occupants or to the building 

that could be aggravated by the work. Verify safe working conditions. Determine whether 

the building has more urgent problems that must be addressed.

Do Not Proceed If:

• The house is not structurally sound.

• The house includes atmospherically vented combustion appliances (except cooking 

appliances).

• The house has knob-and-tube wiring or other electrical hazards.

• The house contains hazardous materials that pose a risk to occupants or workers.

• The house has active water leaks that will not be resolved by the retrofit project.

• Kitchen and/or bath fans are not vented to the exterior.

• The home is not equipped with a whole-house ventilation system.

• The existing roof and/or insulation materials exhibit rot or insect damage or contamination.

!

Remove Wall Cladding and Trim. Remove cladding attachment, trim, and 

decking adjacent to the wall to allow for continuous exterior insulation. REMOVE Prepare the wall sheathing to receive the water and air control membrane.

CLADDING

1

WATER AND AIR 

CONTROL 

MEMBRANE

Install Water and Air Control Membrane. Install a continuous water and air 

control membrane to the existing sheathing. Water and air control membrane 

must also provide the necessary vapor retarder performance.

Install Flashings and Air Control Transitions: Install adhered membranes to 

transition the air control into window and door rough openings and air seal all 

penetrations through the wall. Flash window and door rough openings as well 

as all wall penetrations.

FLASHINGS AND AIR 

CONTROL TRANSITIONS

DRAIN PIPE

Install Windows and Doors. Reinstall windows and doors or install new 

windows and doors in properly flashed openings. Air seal window and door units 

to the air control transition membranes at interior perimeter of window and door 

units.

FURRING STRIPS

Install Furring Strips. Install over insulation board and attach to structure 

through the insulation board. Install furring strips in a vertical orientation only.

Install Cladding and Trim. Attach wall cladding and trim to furring strip.

CLADDING AND TRIM

WINDOWS 

AND DOORS

Remove Windows and Doors To Allow Flashing and Air Control 

Transitions. Remove the windows to allow installation of air control transition 2 membranes and flashings in the window and door openings.

3

4

INSTALL WINDOWS 

AND DOORS

5

MINERAL FIBER 

INSULATION BOARD

6 Install Insulation Board. Install over the water and air control membrane. Butt 

joints tight. When installing multiple layers, offset seams in two directions.

7

8
xiv 

Progression Summary: 

High Performance Mineral Fiber Foundation Wall Retrofit

INSPECT AND 

ASSESS THE 

HOME

Inspect and Assess the Home: Identify and address risks to occupants or to the building 

that could be aggravated by the work. Verify safe working conditions. Determine whether 

the building has more urgent problems that must be addressed.

Do Not Proceed If:

• The house is not structurally sound. 

• Framing exhibits rot or insect damage. 

• Underground electric and gas service to the building or passing near the foundation has not 

been located. 

• Soil around the foundation is contaminated (e.g., with lead, pesticides). 

• The house includes atmospherically vented combustion appliances (except cooking 

appliances). 

• The house has knob-and-tube wiring or other electrical hazards. 

• The house contains hazardous materials that pose a risk to occupants or workers. 

• The house has active water leaks that will not be resolved by the retrofit project. 

• Kitchen and/or bath fans are not vented to the exterior. 

• The home is not equipped with a whole-house ventilation system.

!

METAL CLOSURE/ 

TRANSITION 

FLASHING

Install a Continuous Metal Closure and Transition Flashing at Top of 

Foundation Wall. Seal to foundation wall with bituminous flashing and sealant. 

Seal lapped seams with bituminous membrane flashing or bituminous sealant.

Install Ground Roof/Foundation Skirt. Lay rubber roofing or similar across 

bottom of excavation (or over insulation) and attach to foundation with retaining 

bar.

GROUND ROOF/ 

FOUNDATION SKIRT

DRAINPIPE

Install Perforated Drainpipe at Low End of Ground Roof/Foundation Skirt. 

Wrap drainpipe in clean aggregate and filter fabric. Slope drainpipe to storm water 

collection or to daylight outlet. DO NOT connect drainpipe to foundation drain.

MINERAL FIBER 

INSULATING 

SHEATHING

Install Insulation Board to Exterior of Foundation Wall. Butt insulation tight 

to underside of metal closure and extend to top of ground roof/foundation skirt.

Install a Protective Finish Over Mineral Fiber Insulation Board. Install a 

non-moisture-sensitive, non-UV-sensitive, impact-resistant protective finish 

PROTECTIVE over the insulation from the top of insulation to the level of finished grade.

FINISH

EXCAVATE

PERIMETER

Excavate Perimeter. Excavate to a depth of at least 2 ft below grade and 4 ft 

from foundation wall. Bottom of excavation to slope at least 5% away from 

foundation.

2

3

1

Optional Step: Install Insulated Foundation Skirt. Line bottom of excavation with 4 in. 

clean aggregate. Install at least 3 ft wide non-moisture-sensitive rigid insulation (e.g., XPS or 

foam glass).

UNDERGROUND 

UTILITIES

4

5

6

Locate Underground Utilities. Locate utilities serving the building or passing near the 

foundation. Implement measures to ensure the protection of these through the project.
1 

Introduction

This Measure Guideline provides details and procedures for high performance retrofit using 

insulation board composed of mineral fiber material. Specifically, the guide demonstrates 

techniques for retrofitting three major enclosure components: roofs, walls, and foundation walls. 

The strategies and procedures developed in this guide are directed to wood-framed residential 

buildings with sloped roofs and cast concrete, block, or brick masonry foundation walls. The 

approach supported in this guide could also be adapted for use over masonry-clad or bearing 

masonry structures.

Table 1 shows the minimum assembly R-value that would constitute a high R-value enclosure 

for the various International Building Code (IBC)/International Energy Conservation Code 

(IECC) climate zones and pertinent enclosure components. These values are based on work by 

Straube (2010). A high performance retrofit, sometimes referred to as a deep energy retrofit 

(DER), results in enclosure components that meet these high R-value targets.

Table 1. Recommended Minimum R-Value for High R-Value Enclosures

Climate

Zone

Building Enclosure Component

Wall Compact

Roof

Basement

Wall Slab Edge

1 10 35 5 None

2 15 40 10 5

3 20 45 10 7.5

4 25 45 15 7.5

5 30 50 15 10

6 35 60 20 10

7 40 65 25 15

8 50 75 35 20

DER has been shown to provide a path to net zero energy ready homes for existing homes (Gates 

and Neuhauser 2013, 2014). High performance enclosure retrofit can position an existing 

building to perform at the level of best-in-class new construction. Retrofitting a wood-framed 

enclosure with thick layers of foam plastic insulation board is a proven high performance retrofit 

technique. 

An exterior retrofit is generally more favorable than an interior retrofit because it is less 

disruptive to the living space and typically allows a structure to remain occupied during the 

project. Exterior retrofit also offers significant advantages for building durability by reducing the 

likelihood of cold weather condensation within the structure. 

However, Ueno (2010) observed that although thick insulation board virtually eliminates the risk 

of condensation from outward vapor drive (cold weather condensation), vapor-impermeable 

insulation board can make a wall more vulnerable to water leaks than walls without insulation 

board. Homes built more recently often incorporate engineered wood sheathing (oriented strand 

board, OSB) and rim boards. When these elements are insulated to the interior with closed-cell 

spray-applied polyurethane foam (SPF) insulation, drying to the exterior becomes critical and 
2 

foam plastic insulation board applied directly over the wall could present a problem (Lstiburek 

2013b). Mineral fiber provides a vapor open insulation board that is key to making these 

assemblies both high R-value and moisture safe.

This Measure Guideline is important to the high performance retrofit industry because it 

demonstrates techniques for using vapor-open, noncombustible, mineral fiber insulation board in 

a high performance enclosure retrofit. 

This Measure Guideline includes a review of decision criteria pertinent to the selection of a 

mineral fiber-based retrofit strategy. These criteria include relative cost, combustibility, moisture 

performance, cladding attachment, trade resources, as well as other considerations associated 

with the insulation material.

Risks that must be addressed with a high performance enclosure retrofit generally, and with a 

mineral fiber-based enclosure retrofit specifically, are outlined. Proper techniques for moisture 

management as well as climate-specific considerations are reviewed. Cladding attachment 

considerations are also discussed.

Although the Measure Guideline does not include any recognized fire resistance rated details or 

assemblies, it does present methods to improve the fire resistance of the retrofit assembly.

This Measure Guideline is intended to support contractors implementing a mineral fiber-based 

high performance enclosure retrofit as well as designers looking to design a high performance 

enclosure retrofit using an alternative to foam plastic insulation. The Measure Guideline may 

also be helpful to building owners wishing to learn more about strategies available for high 

performance retrofit of wood-framed residential buildings. 
3 

1 Assess the Home

1.1 Risk Identification

1.1.1 Identify Site Risks

Before a significant retrofit project is conducted, the home must be assessed to determine 

whether significant, if hidden, problems should be addressed as higher priorities than an 

enclosure performance upgrade. Also, changes to the building enclosure will have a significant 

impact on the dynamics of water, air, vapor, and heat flow within the home. Certain measures 

should be implemented prior to, or as part of, any significant enclosure retrofit project to ensure 

that these changing dynamics do not have negative ramifications for health and safety or for 

building durability. Measures to be implemented prior to or as part of the enclosure retrofit 

outlined in this Guide relate to: 

• Remediation of existing hazardous conditions

• Combustion safety

• Indoor air quality. 

The measures described to address indoor air quality include mechanical ventilation and soil gas 

control. These are not the only means to ensure good indoor air quality. However, effective 

mechanical ventilation and soil gas control are essential aspects of the building (as contrasted to 

furnishings, equipment, materials, etc. that people might bring into a building) that provide the 

occupants a means to control contaminants and respond to indoor air conditions. 

1. Remediate hazardous conditions. 

Before a DER project begins, any hazardous conditions must be remediated that will be affected 

(e.g., exposed or aggravated) by the planned work. Also, it is wise to ensure that more serious 

problems are not lurking. A high performance enclosure retrofit—however worthy the goals may 

be—should not divert resources from where they are more urgently needed. 

Before embarking on a project as outlined in this Guide, inspect and assess the building for: 

• Structural integrity of the frame and foundation 

• Safety and serviceability of the electrical system

• Hazardous materials (e.g., lead, radon, asbestos) 

• Rainwater, groundwater, or plumbing water leaks 

• Rot or decay in framing 

• Insect and other pest damage and activity.

The structural system must be sound before high performance retrofit work can begin. Similarly, 

the electrical system must provide basic electrical safety. Knob-and-tube wiring may preclude 

retrofit of the enclosure; a licensed electrician should be consulted to discuss the nature of the 

retrofit and determine whether knob-and-tube wiring should be replaced. Ideally, the electrical 
4 

system would be brought up to date with current code and brought into alignment with current 

and projected building needs. 

Hazardous materials that will be affected by the planned work or that may impact the indoor air 

quality must be remediated and/or removed to avoid exposure to occupants or workers. 

Any bulk water issues, whether these relate to rainwater leaks, groundwater infiltration, or 

plumbing system leaks, must be repaired before the enclosure retrofit project proceeds, unless 

the planned work will remove the source of the bulk water issue (e.g., if the roof surface or 

leaking section of plumbing is to be replaced as part of the project).

Any framing that shows signs of rot or decay should be replaced. This frequently applies to the 

framing sill in older buildings. Also, any framing that exhibits preconditions for rot or decay—

i.e., damp wood—will require remediation.

Past insect and pest damage must be evaluated for impact on the building. Ongoing insect and 

pest activity must be remediated.

Follow applicable laws and industry procedures for mitigation of hazardous materials. Engage 

the services of a qualified professional when needed.

2. Ensure combustion safety. 

Atmospherically vented (or naturally aspirated) combustion appliances are not appropriate for 

high performance homes. With the exception of gas cooktops, ranges, and wall ovens, 

combustion appliances should be direct-vented or direct exhaust-vented equipment. These types 

of appliances are significantly more energy efficient than natural draft appliances. If replacing 

equipment is not feasible, draft inducer retrofit kits can provide fail-safe forced-draft 

performance for some types of combustion appliances. This can address the combustion safety

issue; however, adding forced-draft operation alone is unlikely to have a significant impact on 

energy performance. 

Gas cooktops, ranges, and wall ovens must be equipped with a range hood that is ducted to the 

outside. 

Solid fuel-burning stoves (e.g., wood stoves and pellet stoves) if not equipped with a fail-safe 

draft inducer, must have a tight-fitting loading door (and no permanent openings or leaks into the 

firebox or flue) and outdoor combustion air ducted to the firebox. If any combustion appliance 

vents through a chimney, the flue should be inspected to ensure that it is in good condition. The 

flue must be repaired if it exhibits any deficiencies. 

Attached garages present a potential source of carbon monoxide and other contaminants that 

could infiltrate into the home. Consult the Indoor airPlus guides for specific guidance on 

treatment of attached garages.

If the house has combustion appliances of any kind or an attached garage, carbon monoxide 

alarms complying with Underwriters Laboratories 2034 should be placed in reasonable 
5 

proximity to the combustion appliances, in any regularly occupied space adjoining an attached 

garage, and outside each separate sleeping area in the immediate vicinity of the bedrooms.

3. Ensure adequate ventilation

Mechanical ventilation is an essential feature of high performance homes. Ventilation is needed 

for source control at the location of contaminant sources (e.g., kitchens, bathrooms, craft areas) 

as well as for distribution of fresh air and dilution of general contaminants. The distribution of 

fresh air and dilution of general contaminant is referred to as background or whole-house

ventilation. 

The 2012 International Residential Code (2012 IRC) provides code minimum requirements for 

ventilation systems, including the ventilation rate capacity for background/whole-house 

ventilation and source control ventilation. This Guide aims to provide additional guidance 

toward meeting the high performance objectives of DER projects. 

4. Control soil gas. 

Before any enclosure retrofit project begins, measures must be taken to prevent entry of soil 

gases into the home. Radon is a soil gas with significant and well-documented health risks. Air 

moving through soil also carries significant moisture and may carry other contaminants such as 

mold spores, herbicides, pesticides, and methane. 

As a minimum soil gas control measure, cracks and holes in the foundation walls and basement 

slab must be sealed. Because of the need for soil gas control, it is important that any penetrations 

made through ground-contact assemblies (slabs and foundation walls) are sealed. Sump pits must 

have airtight and gasketted covers.

Implementation of a soil gas venting system is strongly recommended. Any significant work to 

the roof or basement/crawlspace provides an opportunity to establish such a system. 

A soil gas venting system essentially provides the soil gas a direct pathway from below the house 

to the outdoors so that it does not move through the indoor living space. If needed, a fan can be 

added to the vent pipe to actively move soil gases from beneath the basement floor to the outside. 

For additional information on soil gas control, see Radon Fan and Vertical Radon Ventilation 

Pipe on the Building America Solution Center website.

1.1.2 Identify Work Risks

In addition to the hazardous material risks indicated above, other risks to worker and building 

safety must be addressed before work commences. 

1. Locate gas and electric utilities. 

The foundation retrofit measures described in this guide require excavation adjacent to the 

foundation. Before foundation retrofit work begins, any underground gas or electric utilities in 

the vicinity of the excavation must be located. 
6 

Overhead wires could present a safety hazard for wall and roof retrofit measures. Work and 

staging in the vicinity of overhead wires must be carefully planned to provide safe working 

conditions. 

2. Assess staging needs.

The wall and roof retrofit measures described in this guide require ladders, staging, or 

mechanical lifts. Carefully review the area around the building to assess the suitability of the 

ground to support ladders, staging, or mechanical lifts.

1.2 Assess the Home To Determine Suitability of Options and the Need for

Additional Control Measures

1.2.1 Roof Measure

Investigate the roof assembly to determine whether it has vapor retarders, and if so, what type. 

Examples of vapor retarders of concern could be class I and class II types such as OSB 

sheathing, closed-cell SPF insulation to the underside of the roof sheathing, kraft or foil facings 

on fibrous insulation, a polyethylene vapor retarder, and plaster finish with oil-based paint.

Assess the roof and wall structural systems to determine whether they can support a “chainsaw” 

approach. If the roof overhang framing is part the roof truss or if roof rafters are supported 

beyond the top of the wall on cantilevered framing, a “chainsaw” approach is not recommended.

1.2.2 Foundation Measure

The exterior foundation retrofit described in this Guide requires that the foundation wall surface 

be relatively flat. If the foundation wall is constructed of field stone or fractured block, other 

retrofit strategies should be pursued.

The exterior foundation retrofit described in this Guide also requires excavation around the 

perimeter of the building. Assess whether there are impediments to excavation. Excavation 

necessitates locating underground utilities in the vicinity of the planned excavation. 

It will also be important to assess how surface water and roof runoff can be drained. Does the 

site allow a drain to daylight? Will a storm water collection or drywell be required?
7 

2 Decision-Making Criteria

2.1 Cost and Performance

Cost and performance are intricately linked and have to be studied in conjunction to determine

the best choice per the decision-maker’s goals and objectives. Installation costs for the retrofit 

solutions described in this Measure Guideline can be expected to vary widely from estimates in 

the referred sources to field experience depending on such factors as contractor experience, 

prevalent region practices, material costs, and the particular circumstances of the project. It is 

worth noting that the range is sometimes a factor of 5 to 10. 

2.1.1 Roof Retrofit

As with the walls, the National Residential Efficiency Measures Database (NREMD) does not 

directly provide a cost estimate for retrofitting insulating board to wood-framed roof assemblies.

The retrofit measures provided that are relevant to a conditioned attic include both cavity 

insulation and insulation board. For a retrofit situation, it may reasonably be the mode that preretrofit case involves an insulated attic space; therefore, insulating within rafter cavities would be 

a necessary part of the measure. The NREMD does not provide costs for removal of roofing but 

does provide cost estimates for replacing an asphalt roof with a unit cost range of $1.90/ft2 to 

$4.30/ft2 (see Table 2). 

Table 2. NREMD Unit Costs for

Insulation Board and Cavity Insulation Roof Retrofit ($/ft2

) 

Retrofit Description

(Cavity Insulation, 

Insulation Board)

Nominal R-Value Cost Range 

($/ft2

) 

R-19 Fiberglass, 3 in. XPS* 34 2.10–3.60

R-19 Fiberglass, 4 in. XPS 39 2.50–4.20

R-30 Fiberglass, 3 in. XPS 45 2.40–4.10

R-30 Fiberglass, 4 in. XPS 50 2.80–4.70

R-38 Fiberglass, 3 in. XPS 53 2.60–4.50

R-38 Fiberglass, 4 in. XPS 58 3.00–5.10

R-38 Fiberglass, 5 in. XPS 63 3.40–5.80

* Extruded polystyrene

The National Grid DER pilot projects that Gates and Neuhauser (2014) evaluated pursued a 

roof/attic insulation target of R-60. The projects that met this target with a strategy including 

both insulation board and framing cavity insulation, all used either 4 in. or 6 in. of 

polyisocyanurate (PIC) insulation board. The reported unit costs for this strategy (excluding 

outliers) ranged from $10.05/ft2

 to $21.84/ft2. 

The target thermal performance in the National Grid DER pilot might correspond to the nominal 

values of the NREMD for R-38 fiberglass plus 4–5 in. of XPS insulting sheathing; however, the 

costs reported for the National Grid DER pilot projects would reflect elements beyond the 

insulation. For example, the reported pilot project costs would include removal of existing 

roofing, installation of an air and water control membrane over the existing sheathing, 
8 

installation of a second layer of roof sheathing above the insulation board, and, in many cases 

removal and subsequent reconstruction of roof overhangs. Actual costs for the roof retrofit 

solution described in this guide are expected to be generally higher and more variable than the 

estimates derived from NREMD.

2.1.2 Wall Retrofit

The NREMD does not directly provide a cost estimate for retrofitting an existing wood-framed 

wall with insulation board; however, a composite of measures can be used to develop an estimate 

from this source. The NREMD provides a range and an average cost for various exterior 

insulation measures. The database also provides a figure for the cost of removing wall cladding 

($0.66 regardless of cladding type), and estimated cost ranges for installation of new cladding. 

Table 3 represents these cost data.

Table 3. National Residential Efficiency Measures Database

Unit Costs for Insulation Board Wall Retrofit ($/ft2

) 

Insulation 

Thickness 

and 

Material 

NREMD 

Insulation 

Board 

Measure 

Cost

Cost With 

Removal of Wall 

Cladding and 

Installation of 

Vinyl Siding

Cost With 

Removal of 

Wall Cladding 

and Installation 

of Wood Siding

Cost With Removal 

of Wall Cladding 

and Installation of 

Fiber-Cement Siding

1 in. XPS 0.93–1.60 4.19–5.06 4.89–6.26 4.69–5.96

1 in. PIC 0.86–1.40 4.12–4.86 4.82–6.06 4.62–5.76

2 in. XPS 1.30–2.20 4.56–5.66 5.26–6.86 5.06–6.56

2 in. PIC 1.10–1.90 4.36–5.36 5.06–6.56 4.86–6.26

3 in. XPS 1.60–2.80 4.86–6.26 5.56–7.46 5.36–7.16

Interestingly, the NREMD data do not show a significant cost jump from 1 in. thick insulation 

board to 2 in. of insulation board. Such a cost jump would be expected because with an 

insulation board thicker than 1 1⁄2 in., furring strips would be required for cladding attachment. 

Baker (2012) used data from RS Means to derive estimates of installed cost of insulation board 

(not including cladding) (Table 4). Baker estimated the cost of installing 1.5 in. PIC insulation 

board at $1.56/ft2

, whereas the estimate for 2 in. PIC insulation board is $3.53, a difference of 

$1.97. Given the modest $0.19 cost difference that Baker estimated between 1 in. and 1 1⁄2 in. 

insulation board, it is reasonable to assume that most of the cost difference he projects between 1

1⁄2 in. and 2 in. insulation board is due to the installation of 1 × 4 wood furring strips. Given this, 

Baker’s estimates for the installed cost of insulation board at these thicknesses can be taken to be 

otherwise consistent with NREMD. For insulation board thicker than 2 in., Baker projects 

installation in two layers (recommended practice), which results in another price jump between 2 

in. and 3 in. thickness of insulation board. 
9 

Table 4. Estimates of Insulation Board Costs

Baker (2012)

Insulation Board

Estimated Insulation 

Board Installed Cost

($/ft2)

Cost Increment

($/ft2 Difference 

Relative to Previous)

1 in. PIC 1.35 –

1 1⁄2 in. PIC 1.56 0.21

2 in. PIC With 1 × 4 Wood 

Furring 3.53 1.97 

3 in. PIC in 2 Layers With

1 × 4 Wood Furring 4.99 1.46 

4 in. PIC in 2 layers With

1 × 4 Wood Furring 5.38 0.39 

Gates and Neuhauser (2014) reported on the experience of 42 DER projects that participated in a 

National Grid-sponsored pilot program. For 36 projects that implemented a wall retrofit 

including 4 in. of insulation board (in two layers, with wood furring strips), the reported energyrelated (e.g. excluding siding and trim) unit cost (excluding outliers) ranged from $4.67/ft2

 to 

$19.15/ft2. Estimates derived from NREMD or from RS Means are within the range reported by

Gates and Neuhauser; however, the data from the National Grid DER pilot provides evidence 

that the range for costs in actual projects is likely to be large.

2.1.3 Translating the Cost of Foam Plastic Insulation Board to Mineral Fiber

Insulation Board

The above measure cost estimates all use data for foam plastic insulation board. Cost data for 

residential mineral fiber insulation board are not widely available in the United States. Wilson 

(2013) used data from a single building supply house for a benchmark comparison. Wilson 

reported these cost in terms of board feet (bf) of material. Given the R-value/inch of the material, 

the bf cost can be used to derive a cost/ft2

-R-value (Table 5). This is a very useful metric for 

comparing materials and for deriving a unit material cost estimate for meeting a given R-value 

assembly target. 

Table 5. Board-Foot Material Costs for Various Insulation Board Materials

From a Single Supplier and the Resulting Cost per Unit Area R-Value ($/ft2

-R) 

Insulation Board Material

Board Foot 

Cost

($/bf)

R-Value

per Inch

Cost per Unit Area

R-Value Cost

($/ft2-R)

Comfort Board Insulated 

Sheathing 0.64 4 0.160 

PIC 0.48 6.5 0.074

Foil-Faced,

Fire Exposure-Rated PIC 0.75 6.5 0.115 

XPS 1.07 5 0.214
10 

According to data from this one source, the material cost relative to thermal resistance for XPS is 

roughly 2–3 times that for an equivalent amount of thermal resistance provided by PIC. The 

material cost relative to thermal resistance for mineral fiber insulation board appears to be 

somewhere between that of XPS and PIC. Therefore, one might expect that the cost for 

insulation board retrofits using mineral fiber would be comparable to otherwise similar solutions 

that use foam plastic insulation board. 

It is worth noting that the NREMD data do not show the same cost difference between XPS and 

PIC as the data from one building supply outlet that Wilson reported. Material costs are thus 

likely to vary considerably between markets. 

In addition to material cost difference, other factors would influence cost difference between 

mineral fiber retrofit solutions and otherwise similar retrofit approaches that employ foam plastic 

insulation board. The fibers from mineral fiber insulation can cause skin irritation. This may be a 

considerable challenge to installation of mineral fiber insulation board in warmer weather, when 

maintaining full skin coverage may cause workers to be uncomfortable. The author observed that 

mineral fiber may also increase the risk of eye injury on the job site. In one construction project 

in which the author participated, construction was delayed on multiple occasions when a worker 

was taken for urgent medical treatment when he apparently rubbed his eye after handling mineral 

fiber material. 

Because mineral fiber has lower thermal resistance per unit thickness than either PIC or XPS, 

mineral fiber assemblies will require greater thickness to achieve the same nominal R-value. 

Therefore, a mineral fiber insulation board retrofit may require longer screws and more material 

for trim returns than an otherwise similar retrofit strategy using either PIC or XPS. 

Also important to installation cost is the weight of the insulation board. As shown in Table 6, 

mineral fiber insulation board is more than 6 times heavier than either PIC or XPS for a given Rvalue and area. This will affect the effort needed to move material into place and brace it while 

fastening. The relative weight of mineral fiber insulation board as well as general strength 

characteristics of the material typically require use of smaller pieces of material. This would 

impact the time and effort required to cover a given area of wall or roof with insulation board.

Table 6. Weight per Unit Area R-10 Insulation for Various Insulation Board Materials (lb/ft2) 

Insulation Board Material Board Foot Cost

($/bf)

R-Value per 

Inch

Weight per Unit 

Area at R-10 

(lb/ft2)

Comfort Board Insulated 

Sheathing 8 4 1.67 

PIC 2 6.5 0.26

XPS 1.3–1.55 5 0.18-0.26
11 

Fire Separation Distance

The International Residential Code for 

One and Two Family Dwellings (IRC) 

requires that assemblies have a 1-hour 

fire-resistance rating if the minimum fire 

separation distance between structures 

is 5 ft or shorter. Under the IBC, the 

requirement for fire-resistance rating 

applies with the minimum fire 

separation distance is 10 ft or shorter. 

Very few listed assemblies contain 

insulation board that carries the 

required fire-resistance rating. The IBC 

provides a potential avenue for the use 

of mineral fiber insulation board that 

relies upon interpretation by the 

building official. Section 703.2 reads:

Where material, systems, or 

devices that have not been tested 

as part of the fire-resistance-rated 

assembly are incorporated into 

the building element, component 

or assembly, sufficient data shall 

be made available to the building 

official to show that the required 

rating is not reduced.

To estimate the magnitude of these various factors 

beyond material cost would be mere speculation. In 

time, experience of contractors will yield approximate 

installation costs for mineral fiber insulation board 

retrofit solutions.

2.2 Fire Code Issues

Before deciding to use mineral fiber insulation board 

in the retrofit, it is important to determine whether its 

fire resistance property is a code issue. Mineral fiber is 

a noncombustible material that, at adequate thickness, 

is recognized in codes as providing a thermal barrier. 

Mineral fiber insulation achieves its fire resistance 

without the use of chemical flame retardants such as 

those used in foam plastic insulation materials.

Exterior retrofit systems using mineral fiber insulation 

board can be constructed such that they offer enhanced 

fire protection. However, as noted by Lstiburek 

(2013a), mineral fiber insulation board assemblies 

have not been “officially burned” to earn recognition 

as fire-resistance rated assemblies. Design of systems 

to meet fire-resistance rating requirements is beyond 

the scope of this guide. 

2.3 Moisture Performance

The decision about the robustness of a moisture control assembly depends on the decisionmaker’s willingness to pay. Design of retrofit assemblies must consider management of bulk 

water loads, interior water vapor loads, and exterior water vapor loads. For roofs and walls, the 

principal bulk water load is generally related to rain and (in some climates) melting snow. 

Capillary transfer of water will impact foundation assemblies and may impact the base of a 

frame wall that is not separated from the foundation by a capillary break. Surface water, roof 

runoff, and groundwater are typical bulk water loads that must be managed by the foundation. 

Irrigation may also contribute a bulk water load that impacts foundation walls and above-grade 

walls. 

Interior water vapor loads apply to assemblies of occupied structures that use heating systems 

and/or that have significant interior moisture generation (e.g., swimming pool, greenhouse, 

extensive cooking). 

Exterior water vapor loads apply to assemblies of occupied structures that include mechanical air 

conditioning. Exterior water vapor loads are also pertinent to structures that have reservoir 

claddings (e.g., brick veneer, stucco, wood, fiber cement) that are exposed to wetting (from rain 

or irrigation) and sunlight.
12 

Exterior insulation board brings the primary sheathing closer to interior conditions and thus 

reduces the condensation potential at the primary sheathing relative to outward (heating season) 

vapor drive. LePage and Lstiburek (2012) found that exterior insulation greater than R-5 is a 

better outward vapor control strategy than interior vapor retarders. Smegal and Straube (2011) 

evaluated thicker vapor-permeable and vapor-impermeable insulation board relative to 

management of interior water vapor loads. Their analysis suggests that with thick insulation 

board the vapor permeability of insulation board is not a significant factor in managing interior 

vapor loads. 

LePage et al. (2013) found through hygrothermal modeling that a high R-value wall with 4 in. of 

exterior insulation provided sufficient condensation resistance in cold climates but that a 

significant rain water leak (5% of wind-driven rain) to the insulation board-sheathing interface 

would most certainly result in damage. 

Ueno (2010) noted some moisture management advantages in the exterior insulation board 

approach to superinsulation: 

For the most part, the retrofit assembly tends to improve durability of the wall, 

due to the drained and ventilated cavity, the redundant drainage planes (multiple 

layers of foam, housewrap), and the reduction in interstitial condensation risk by 

elevating the condensing surface temperature with exterior insulation.

Ueno notes, however, that the loss of drying to the exterior could have durability implications. 

He found that a leak (in terms of percentage incident rain penetration) that is “survivable” (in 

terms of maintaining sheathing moisture content below a critical threshold) in pre-retrofit 

conditions is not survivable when the building is retrofitted with vapor-impermeable insulation 

board. Based on this analysis, Ueno indicated, it is critical to ensure proper flashing when 

implementing an exterior superinsulation retrofit. BSC guidance and review of superinsulation 

retrofit using exterior insulation board has strongly emphasized robust water management (Baker 

2012; BSC 2010; Neuhauser 2011; Pettit 2009; Pettit et al. 2013). 

Smegal and Straube (2011) compared the performance of wood-framed walls with either XPS or 

mineral fiber insulation board. At greater R-value of insulating the mineral fiber showed little 

advantage in managing outward vapor drive compared to the XPS. A difference in simulated 

performance was more noticeable with thinner (lower R-value) insulation board. The hygrothermal analysis also showed some appreciable difference in the drying potential for the mineral 

fiber assemblies in simulated winter and summer conditions. For OSB or engineered wood 

products, rapid drying from moisture concentrations would be more critical. Plywood or sawn 

wood sheathing offers some benefit of hygric redistribution within the material (Lstiburek 2010).

Lstiburek (2013a) observed that OSB sheathing with low permeability materials to interior and 

low permeable or impermeable insulation board require an air gap between sheathing and 

insulation board for drying and hygric redistribution. Lstiburek also notes that vapor open 

insulation board can provide useful drying without this added air gap. 

Inward vapor drive is a risk factor associated with warm-humid climates, air conditioning, and 

reservoir claddings. Dérome et al. (2010) observed that warm-humid and mixed-humid climates 
13 

pose a risk to vapor-permeable wall assemblies. They further observed that rain-wetted reservoir 

claddings exposed to strong solar radiation (sunlight) can produce a very strong inward vapor 

drive. 

Through hygrothermal simulation, Lepage and Lstiburek (2012) found that a vapor control 

membrane with a vapor permeance of up to 10 perms is sufficient to protect OSB sheathing from 

sustained elevated moisture content, provided that no significant vapor retarders are placed to the 

interior of the sheathing (e.g., polyethylene or vinyl wall covering). This study evaluated vapor 

control membranes with a permeance of 0.1, 1, 10, and 50 and located an inflection point in wall 

behavior with a vapor control of 10 perms. This analysis showed that vapor control at the 

exterior of sheathing (between vapor permeable insulation board and structural sheathing) is 

more important to protecting the wall where drying to the interior is impeded by a significant 

vapor retarder such as may be represented by vinyl wall covering, polyethylene, or foil facing. 

2.4 Cladding Attachment

Rigid foam insulation board has long been established as a suitable substrate behind furring 

strips used for cladding attachment. The compressive resistance of mineral fiber insulation board 

is appreciably less than the compressive resistance of rigid foam typically used for insulation 

board. 

As summarized by Holladay (2011), laboratory testing has demonstrated that a wall 

configuration using 8/ft3

 mineral fiber insulation and furring strips for cladding attachments can 

support common cladding systems with negligible initial as well as long-term deflection. 

However, long-term testing in exposed conditions, with significant diurnal and seasonal 

temperature variations (unlike in a lab) shows considerably more movement of furring strips 

attached over insulation board and with imposed 

cladding loads. Ongoing research by BSC and Building 

Science Labs has shown that mineral fiber insulation 

board performs very similarly to PIC and XPS relative to 

movement of furring strips under loads representative of 

lightweight (e.g., vinyl, wood siding) to medium weight 

(e.g., stucco) cladding. This research has yielded the 

conclusion that cladding weight should be limited to 10 lb/fastener over insulation board 

(including mineral fiber insulation board) at thicknesses up to 4 in. Further research is needed to 

confirm the capacity of furring strip cladding attachment with thicker insulation board. 

A challenge noted for installation of furring strips over a “softer” insulation board such as 

mineral fiber insulation board, is maintaining plumb and planar furring strips (Cowan and Walsh 

2013). The initial force of setting the fastener through the furring strip can easily compress the 

mineral fiber insulation board. Contractors have developed various methods to assist in 

maintaining plumb and planar furring. 

Critical Takeaway

Space screw fasteners in furring 

strips such that the cladding load 

amounts to no more than 10 lb per 

fastener at thicknesses up to 4 in.
14 

2.5 Other Material Characteristics or Criteria

Styrene foam plastic building insulation is 

manufactured with brominated flame retardants.

These are widely recognized as persistent organic 

pollutants (Wilson 2013). Other foam plastic 

building insulation materials also incorporate 

chemical flame retardants. As noted above, mineral 

fiber insulation does not use added chemical flame

retardants.

Mineral fiber insulation products currently available 

do, however, use formaldehyde-based binders. As 

such, certain building labeling and recognition 

programs, such as the Living Building Challenge, 

preclude the use of mineral fiber building insulation. 

Wilson (2013) relayed manufacturers’ explanations 

that the high temperature production process drives 

off nearly all of the free formaldehyde. Wilson also 

alluded to test data showing formaldehyde emissions 

from mineral fiber insulation to be below or near 

background levels.

2.6 Trade Resources

Despite recent gains and the development of manufacturing capacity in the United States, the 

distribution network for mineral fiber insulation board is still nascent. Mineral fiber batt 

insulation is—and has been—widely available; however, mineral fiber insulation board 

sheathing is not stocked in “big box” consumer-oriented building supply retailers. 

Experience with insulation board installation is still far from universal in the residential building 

sector. Immediate adoption of mineral fiber insulation board retrofit solutions is probably best 

suited to contractors who have been trained in these techniques, because they require exacting 

attention to details.

Strategies To Achieve Plumb and Planar 

Furring Strips

A persistent challenge with installing furring 

strips over mineral fiber insulating is 

maintaining plumb and planar furring strips. 

Setting and adjusting fasteners to plumb 

furring strips and plane out a wall can be 

time consuming. Strategies that contractors 

have developed to make this step easier 

include:

• Hand setting cap nails to act as spacers 

prior to installing furring strips. The cap 

nails also mark the location of framing.

• Using broken thread fasteners (fasteners 

with an unthreaded section of the shaft 

that allows the fastener to be firmly set 

into the structure before threads engage 

the furring strip). 

• Predrilling furring strips.

Methods that risk damaging the air and 

water control membrane, such as coring 

through the mineral fiber insulation board 

with a hole saw should be avoided.
15 

3 Technical Description

3.1 High Performance Mineral Fiber Retrofit Assemblies

The high performance mineral fiber retrofit solutions are described in outline below. 

3.1.1 Mineral Fiber Retrofit Roof Assembly

From interior to exterior the retrofit roof assembly is as follows (see Figure 1 and Figure 2): 

• Fibrous cavity insulation (SPF also acceptable with conditions) 

• Existing roof sheathing

• Air and water control membrane 

• Mineral fiber insulation board as needed for condensation control and high R-value 

performance 

• Sheathing (for cladding attachment) fastened to structure through the mineral fiber 

insulation sheathing. Where roof cladding is vented, furring strips are used.

• Water control membrane (underlayment and ice and water membrane)

• Roofing (shingles). 

Note that some variations are inherent with different roof cladding systems such as metal or tile 

roof cladding. 

3.1.2 Mineral Fiber Retrofit Wall Assembly

From interior to exterior the retrofit wall assembly is as follows (see Figure 3 and Figure 4): 

• Existing interior finish

• Fibrous cavity insulation (SPF also acceptable with conditions) 

• Existing wall sheathing 

• Air and water control membrane 

• Mineral fiber insulation board with R-value per Table 8 for condensation control and 

high R-value performance

• 1 × 4 furring strips fastened to the structure through the mineral fiber insulation board 

• Cladding and trim. 

The foundation retrofit strategy also includes groundwater and roof runoff control measures. A 

ground roof of rubber roofing or similar material is installed at the bottom of the excavation and 

sloped to a perforated drainpipe that is routed to a daylight outlet or to a storm water collection 

system. The drainpipe must not be connected to the foundation drain. In cold climates or in 

houses with crawlspaces or basements, non-moisture-sensitive insulation is placed over clean 

aggregate at the bottom of the excavation before the ground roof is installed. 
16 

Figure 1. Mineral fiber retrofit roof assembly
17 

In high snow-load areas, a vented roof cladding is recommended. This alternative is shown in 

Figure 2 below. 

Figure 2. Mineral fiber retrofit roof assembly with a vented roof cladding
18 

Figure 3. Mineral fiber retrofit wall assembly
19 

Figure 4. Insulated ground roof included with mineral fiber retrofit foundation wall approach
20 

3.2 Material Properties and Criteria for Mineral Fiber Insulation Board

Table 7 lists the material properties necessary or assumed for the mineral fiber retrofit solutions 

described in this Measure Guideline.

Table 7. Material Properties and Criteria for Mineral Fiber Insulation Board

Material Property Criteria Relevant Standard

Density Approximately 8/ft3

Compressive Resistance 5/ft2 at 10% deformation,

8/ft2 at 8% deformation

Hygrophobic moisture sorption 0.1% ASTM C1104

Thermal Resistance R-value 3.8–4.3/in.

Stone Wool

Melting Temperature > 2,000°F

non-combustible at 750°F ASTM E136

Flame Spread < 5 ASTM E84

Smoke Development ≤ 10 ASTM E84

Water Vapor Permeance ~30 U.S. perms @

2 in. thickness

Coefficient of Thermal 

Expansion < 5 10-6 in./in./°F 

3.3 System Interaction

This is a high performance retrofit solution. Approaching from the exterior side, as this retrofit 

solution does, presents an opportunity to completely overhaul the major building enclosure 

functions—water control, air control, vapor control, and thermal control—of the above-grade 

enclosure so that it can provide a very high level of performance well into the future. In keeping 

with this opportunity, the retrofit solutions outlined in this Guide include robust water, air, and 

vapor control measures in addition to high R-value thermal performance. The solutions outlined 

also have the potential to benefit the building enclosure’s “critter” (insect and rodent) control 

performance. 

The performance of the mineral fiber retrofit solutions relative to critical control functions is 

described below. 

3.3.1 Water Control

3.3.1.2 Water Control in Mineral Fiber Retrofit Roof Solution

In the retrofit roof assembly, the new roofing installed above 

insulation board provides the primary water control. The air 

control membrane installed over the existing roof sheathing is 

recommended to be detailed as a water control (backup and 

construction phase water control) membrane. 

To prevent ice dams in high snow load areas (areas with > 50/ft2

ground snow load) the roof cladding nail base sheathing should be vented above the insulation 

Vented Roof Option

Where the ground snow load 

is 50/ft3 or greater, a vented 

roof cladding is recommended 

as a method to further control 

ice dam formation.
21 

board. Vented roofing is accomplished with 2 × 4 on the flat purlins installed between the 

insulation board and the nail base sheathing and then providing eave and ridge vents. Note that 

purlins need not be continuous from the eave to the ridge. Breaks in the purlins can allow for 

cross-ventilation as would facilitate ventilation of complex 

roofs involving hips, valleys, or interruptions such as 

dormers and skylights. 

3.3.1.2 Water Control at the Roof-to-Wall Transition

The roof overhangs provide the transition of bulk water 

control at the roof-to-wall transition.

For the transition from a wall to a lower roof, see the details in Section 4. 

3.3.1.3 Water Control in Mineral Fiber Retrofit Wall Solution

The mineral fiber insulation board material, although hygrophobic, is not suitable for creating a 

drainage plane at the surface of the insulation as may be done with foil-faced PIC or XPS 

insulation board. Instead, a water control membrane is installed on the face of the existing 

sheathing (in a manner similar to new construction) to serve as the drainage plane/water control 

layer. Flashings are then integrated with this drainage plane. 

The flashing details for this system are very similar to those provided in Baker (2012) for 

“Exterior Insulation over Wood Frame Wall Drainage Plane at Face of Wood Frame.”1

 

Some flashings such as kick-out flashing or through-wall flashings that are intended to direct 

water from the drainage plane out over the face of the cladding will need to anticipate the added 

thickness of the insulation and furring strips. 

3.3.1.4 Water Control at the Wall-to-Foundation Wall Transition

The transition of bulk water control at the wall-to-foundation wall transition is provided by a 

sloped metal closure/flashing at the base of the wall retrofit assembly or top of the foundation 

wall retrofit assembly.

3.3.1.5 Water Control in Mineral Fiber Retrofit Foundation Wall Solution

At the foundation wall, this retrofit solution enhances the control of roof runoff and surface water 

near the foundation wall, as shown in Figure 6. The retrofit assembly for the foundation includes 

mineral fiber insulation and cladding at the above-grade portion of the wall as well as a “ground 

roof” or “skirt” with a drainpipe below grade. The treatment on the above-grade surface of the 

foundation wall prevents splash-back and other minor surface water from being absorbed into the 

foundation by capillary action. The retrofit assembly also allows for some drying of moisture 

(e.g., capillary moisture from groundwater) from the foundation wall. The ground roof intercepts 

 

1 The details for exterior insulation with drainage plane at the face of wood framing appear in Appendix A to 

Baker’s report on pages 63–78.

Critical Takeaway

Through-wall and kick-out 

flashings need to be extended 

to accommodate the added 

thickness of insulation and 

furring strips.
22 

roof runoff and surface water that is draining near the foundation and directs this water into a 

drainpipe that conveys it to daylight or a drywell. This drainpipe must NOT be connected to an 

existing foundation drain, because this would result in charging the foundation drain system with 

roof runoff and groundwater. 

Clean stone in a drip trench adjacent to the foundation wall provides a capillary break between 

the soil and the protective insulation finish. This capillary break is important for protecting finish 

material, such as stucco, that is not appropriate for ground contact. The stone also serves to 

dissipate the energy of rain or roof runoff, thereby limiting splash-back. 

A capillary break of clean aggregate is also needed under the rigid insulation used in an insulated 

ground roof/insulated foundation skirt. 

This retrofit approach involves only a shallow excavation around the perimeter of the building 

rather than a full excavation of the foundation walls. The retrofit measures significantly improve 

water management, but the home may still require measures at the interior such as a sump pump 

or an interior perimeter drain to manage elevated groundwater. 

3.3.2 Air Control

3.3.2.1 Air Control in Mineral Fiber Retrofit Wall and Roof Solutions

Mineral fiber insulation is not an air barrier material. In the mineral fiber retrofit assembly for 

the wall and roof, air control is established at the face of the existing sheathing. Often the water 

control membrane can be detailed to serve as both a water control and an air control layer. In 

cases where the sheathing is wood panels (OSB or plywood), it may be possible to establish the 

air control layer at the wood sheathing by taping the seams and sealing penetrations through the 

sheathing. Wood panels may also be added to a roof or wall to serve as an air control membrane. 

In some cases, adding wood panel sheathing of sufficient thickness over existing wood sheathing 

can create a continuous layer of adequate wood thickness for fastener embedment (typically 1 1⁄2 

in. is required). 

3.3.2.2 Air Control at the Roof-to-Wall Transition

With the “chainsaw” retrofit configuration, the air control membrane of the roof connects 

directly to the air control membrane of the wall.

For a non-chainsaw configuration, a sheathing infill extends from the top of the existing wall 

sheathing to the underside of the roof sheathing. This infill sheathing is sealed to the roof 

sheathing, sealed to the air control layer of the wall, and sealed around all penetrations through 

the plane of the infill sheathing/wall sheathing.

For the transition from a wall to a lower roof, see the details under Measure Implementation.
23 

3.3.2.3 Air Control at the Wall-to-Foundation Wall Transition

At the base of the frame wall, the air control membrane is adhered to or sealed to the bottom of 

the wall sheathing. The bottom of the wall sheathing is sealed to the foundation wall. 

3.3.2.4 Air Control in Mineral Fiber Retrofit Foundation Wall Solution

With a cast concrete foundation wall, the foundation wall typically provides the air control layer 

for the assembly. Holes and cracks in the cast concrete foundation wall must be patched and 

sealed. With foundation walls constructed of block, brick, or field stone, effective air control 

relies upon an air control membrane applied at the interior of the foundation wall. 

3.3.3 Vapor Control

Insulation board makes the framing cavity more similar to the conditioned interior. During the 

heating season, insulation board makes the framing cavity and sheathing warmer and drier. 

During cooling seasons or periods of air conditioner use, insulation boards make the framing 

cavity and sheathing colder and potentially wetter. Especially in a building that uses air 

conditioning, but even in a cool climate where air conditioning will not be used, drying to the 

interior is important. Drying to the interior can be inhibited by interior-side vapor retarders such 

as polyethylene, foil-facing or kraft facing on insulation, vinyl wall coverings, tiles, or even 

multiple layers of paint. In a retrofit situation, the presence or absence of interior-side vapor 

retarders may not be known without opening an exterior wall. Exploratory openings should be 

made, if needed, to determine the existing enclosure assembly configuration. 

Super-insulated wall and roof assemblies that use thick exterior insulation board usually have 

sufficient insulation to the exterior of the sheathing to control condensation of interior water 

vapor. The amount of insulation needed to the exterior of the sheathing to control this 

condensation is determined by a number of factors. The dew point of the interior air determines 

the critical temperature above which the sheathing must be maintained. The temperature of the 

sheathing is determined by the outdoor temperature, the indoor temperature, and the part of the 

total assembly R-value that is to the exterior of the sheathing. Infrequent and short-lived 

condensation conditions are typically not a concern for sheathing materials with reasonable 

moisture tolerance such as OSB, plywood, or board sheathing. Condensation that accumulates 

and is sustained over a significant period of time is a concern. Design for air leakage 

condensation control in this context can use the average temperature of the three coldest months 

for a particular location as the outdoor temperature condition. Table 8 shows the ratio of exterior 

insulation R-value to total assembly R-value needed to control the temperature of sheathing 

above the dew point of interior air given interior air at 68°F.
24 

Table 8. Ratio of Exterior Insulation to Total Assembly Insulation for

Air Leakage Condensation Control at 68°F Indoor Temperature

(adapted from Straube 2011)

Indoor Relative 

Humidity

(%)

20 25 30 35 40 50 60

Dew Point of

Interior Air

(°F)

26.6 32 36.6 40.5 44 49.9 54.8

Outdoor 

Temperature

(°F)

Ratio of Exterior Insulation R-Value to

Total Assembly R-Value for Condensation Control

50 0 0 0 0 0 0 0.24

41 0 0 0 0 0.1 0.31 0.48

32 0 0 0.12 0.23 0.32 0.47 0.6

23 0.08 0.19 0.29 0.37 0.45 0.57 0.68

14 0.23 0.32 0.4 0.48 0.54 0.64 0.73

5 0.33 0.42 0.49 0.55 0.6 0.69 0.77

–4 0.41 0.49 0.55 0.6 0.65 0.73 0.8

–13 0.48 0.54 0.6 0.65 0.69 0.76 0.82

–22 0.53 0.59 0.64 0.68 0.72 0.78 0.84

1. Vapor Control in Mineral Fiber Retrofit Roof Solution

Outward vapor drive is controlled in the roof assembly by insulation to the exterior of existing 

roof sheathing. It is important to maintain sufficient 

ratio of exterior insulation (insulation board) to total 

roof assembly insulation. Table 8 shows the ratio of 

insulation needed for various interior humidity 

conditions and an interior temperature of 68°F. 

Inward vapor drive must be managed for all roofs. In 

roof assemblies with plywood or board sheathing and 

fibrous cavity insulation and no interior-side vapor 

retarders the inward vapor drive is managed by allowing drying to the interior. However, if the 

roof assembly includes significant vapor retarders on the interior side of the roof cavity, closedcell foam insulation (SPF or board foam) to the interior of the structural sheathing, or OSB 

sheathing, then additional vapor control measures are needed. In hot-humid climates, the air 

control membrane installed above the existing roof sheathing must be a class II (or lower) vapor 

retarder and also be a water control membrane. In other climates, the air control membrane 

should be a class III (or lower) vapor retarder. Information about classes of vapor retarders has 

been provided by Lstiburek (2011).

3.3.1 Vapor Control at the Roof-to-Wall Transition

See Section 3.3.4.2. 

Key Point

For vapor control in a hot-humid 

climate, the air control membrane 

over the existing sheathing must be a 

class II (or lower) vapor retarder and 

must also be a water control 

membrane.
25 

3.3.2 Vapor Control in Mineral Fiber Retrofit Wall Solution

Condensation caused by outward vapor drive is controlled 

in the wall assembly by insulating to the exterior of 

existing wall sheathing. The ratio of exterior insulation 

(insulation board) to total wall assembly insulation is 

critical to controlling the risk of condensation at the 

sheathing. The ratio needed varies with climate and interior 

conditions (see Figure 5). Table 8 shows the ratio of 

insulation needed for various interior humidity conditions 

and an interior temperature of 68°F. 

The wall assembly manages inward vapor drive through a 

vented cladding and a water and air control membrane over 

the sheathing that is also a class III (or lower) vapor 

retarder. In hot-humid climates, a class II (or lower) vapor 

retarder over the sheathing is appropriate. For walls that 

have a non-reservoir cladding such as vinyl siding and that 

are located in either a dry or cold (climate zone 5 or above) climate, the class III vapor retarder is 

necessary with significant air conditioner use and interior-side vapor retarders only. 

Limiting the Impact of Reservoir 

Claddings 

The water uptake of reservation 

claddings can be significantly reduced 

by preventing water from reaching the 

surface of the cladding. For example, 

large overhangs can shield the 

cladding from incident rain water. 

Paints and coatings can also block 

the capillary pores that wick water into 

the material. For wood and fiber 

cement cladding, it is important to 

prime or paint all sides of the cladding 

pieces—including cut ends—to limit 

the uptake of water through capillary 

action.
26 

Figure 5. Ratio of exterior to total insulation to control

condensation of interior water vapor

3.3.3 Vapor Control at the Wall-to-Foundation Wall Transition

See Section 3.3.4.2. 

3.3.4 Vapor Control in Mineral Fiber Retrofit Foundation Wall Solution

The foundation retrofit assembly permits drying from the foundation wall into the mineral fiber 

exterior insulation. Whether moisture is able to dry to the exterior depends upon the properties of 

the protective finish selected for the above-grade part of the mineral fiber insulation. A sheet 

metal covering would not allow diffusion drying but condensate could safely drain away 

between the metal covering and the insulation board. 

The interior of the foundation wall may still present a condensation surface when interior air dew 

point exceeds the ground temperature. Also, the part of the foundation wall below the foundation 

skirt will remain exposed to ground moisture. Comprehensive vapor management for foundation 

walls may require additional measures to the interior of the foundation wall.

Insulation for Condensation Control

To control condensation of interior water vapor, the sheathing must be maintained above the 

dew point of the interior air. The temperature of the sheathing is determined by the indoor 

and outdoor temperature and by the ratio of insulation outside of the sheathing to insulation

inside of the sheathing. As the outdoor temperature decreases, the amount of insulation 

needed to maintain the sheathing temperature increases. Also, as the interior humidity 

increases the dew point temperature of interior air increases, so the sheathing must be 

maintained at a higher temperature to avoid condensation.
27 

3.3.4 Thermal Control

Table 1 provides the thermal resistance (R-value) targets for the enclosure components addressed 

in this guide. The “Basement Wall” targets define the performance criteria for exterior insulation 

of the foundation wall. The target performance for the insulated foundation skirt (used in cold 

climates or where the home has a crawlspace or basement) is given by the targets for “Slab 

Edge” insulation in the table.

3.3.4.1 Thermal Control in Mineral Fiber Retrofit Roof Solution

The retrofit roof assembly is thermally controlled by insulation board, usually in combination 

with cavity insulation directly to the underside of the sheathing. It is important that the ratio of 

exterior insulation board to total assembly thermal resistance is as needed to control 

condensation. See Section 3.3.1. 

3.3.4.2 Thermal Control at the Roof-to-Wall Transition

In a “chainsaw” configuration, the continuity of thermal control is inherently achieved by direct 

connection between roof insulation board and wall insulation board. In cold climates, continuous 

insulation at the transition is important to the control of condensation or elevated relative 

humidity at the thermal bridging elements represented by framing. 

In non-chainsaw configurations, the roof insulation board is continuous onto the overhang. The 

wall insulation board is fit around projecting framing and butted to the roof sheathing. Closedcell SPF is used to complete the transition of air, vapor, and thermal control at non-chainsaw 

roof-to-wall transitions.

For the transition from a wall to a lower roof, see the details in Section 4. 

3.3.4.3 Thermal Control in Mineral Fiber Retrofit Wall Solution

The retrofit wall assembly is thermally controlled by insulation board, usually in combination 

with insulation in the framing cavities of exterior walls. It is important that the ratio of exterior 

insulation board to total assembly thermal resistance is as needed to control condensation. See 

the Section 3.3.4. 

3.3.4.4 Thermal Control at the Wall-to-Foundation Wall Transition

Metal flashing at the base of the wall represents a thermal bridging element with respect to the 

insulation board. When connected to the mass of the foundation wall, the impact is dispersed and 

should not represent a specific cold-weather condensation risk. 

The bottom of the exterior wall retrofit assembly should extend past the bottom of the wood 

sheathing where possible to ensure that the sheathing is maintained closer to the interior 

conditions. 
28 

Continuity of the thermal control is improved by cutting the bottom of the wall insulation board 

and the top of the foundation wall insulation board on an angle to fit snug against the sloped 

metal flashing/closure between the foundation and wall exterior retrofit treatments.

3.3.4.5 Thermal Control in Mineral Fiber Retrofit Foundation Wall Solution

The insulation board installed at the exterior exposed part of the foundation wall should at least 

meet the high R-value target for basement walls. This is true even if the interior is insulated as 

the exterior exposed part of the foundation wall represents a more significant heat transfer 

surface than the below-grade (by more than 1 ft) sections. To the extent that a significant part of 

the foundation wall remains in contact with ground below the exterior insulation treatment, the 

foundation wall will remain significantly ground coupled. Therefore, additional insulation to the 

interior may be warranted to improve comfort conditions. 

The R-value of the insulated foundation skirt (used in cold climates or where the home has a 

crawlspace or basement) should be at least as given by the targets for “slab edge” insulation in 

the table. Because of the position of the foundation skirt insulation, the insulation material must 

be a rigid material with robust compressive strength and the material must be non-moisture 

sensitive. XPS and foamed glass rigid insulation are appropriate materials for this application. 

Even with these relatively non-moisture-sensitive materials, the insulation is recommended to be 

laid over a capillary break of clean aggregate. 

3.4 Climate Considerations

Mineral fiber insulation board is a vapor-permeable material that supports outward drying of 

assemblies. Because of its high vapor permeability the material offers negligible resistance to 

inward vapor drive. Inward vapor drive occurs when the ambient air is humid and the interior of 

the enclosure is cooler than ambient air. This condition is typical of buildings when air 

conditioning is in operation. It is a sustained condition in hot-humid climates.

Inward vapor drive also occurs—and can be significant—when a wetted reservoir cladding is 

exposed to direct solar radiation. This type of inward vapor drive can affect buildings with 

reservoir claddings regardless of the climate.

Inward vapor drive presents a risk to moisture-sensitive materials located in a part of the 

assembly where it would lead to condensation or elevated relative humidity. 

To provide control of exterior water vapor, a class III (or lower) vapor retarder between mineral 

fiber insulation board and sheathing is the base recommendation for mineral fiber framed 

assembly retrofit solutions. In hot-humid climates, a class II (or lower) vapor retarder over the 

sheathing is recommended.

For walls that have a non-reservoir cladding, such as vinyl siding, and that are located in either a 

dry or cold (climate zone 5 or above) climate, the class III vapor retarder is necessary with 

significant air conditioner use and interior-side vapor retarders only. 
29 

4 Measure Implementation

4.1 High Performance Mineral Fiber Retrofit Roof Assembly

4.1.1 Scope of Work

1. Remove roof cladding and prepare the roof sheathing for air and water control 

membrane. 

2. Implement a “chainsaw” retrofit where structural configuration of the roof permits.

3. Install a continuous air and water control membrane over the roof sheathing to provide 

vapor control in accordance with code. Transition the roof air and water control 

membrane to adjacent assemblies.

4. Install mineral fiber insulation board in accordance with code to satisfy the high R-value 

performance target for the assembly and for adequate condensation control (the higher Rvalue requirement shall govern). 

5. Install sheathing as a nail base for roof cladding. Fasten the sheathing to the roof structure 

through the insulation board. 

OR

Install purlins for ventilated roof sheathing. Fasten the purlins to the roof structure 

through the insulation board. Install sheathing as a nail base for roof cladding. Fasten the 

sheathing to the purlins. 

6. Install roof underlayment, ice and water membrane, flashing, and roofing per new 

construction best practices.

4.1.2 Climate-Specific Factors

In hot-humid climates, the air and water control membrane between the mineral fiber insulation 

board and the roof/wall sheathing must be a class II (or lower) vapor retarder.

4.1.3 Field Inspection

Identify and address risks to occupants or the building that could be aggravated by the work. 

Verify safe working conditions. Determine whether the building has more urgent problems that 

must be addressed. Determine the feasibility of the retrofit solution and of options. 

Inspect and assess the building for: 

• Structural integrity of the frame and foundation 

• Safety and serviceability of the electrical system

• Hazardous materials (e.g., lead, radon, asbestos) 

• Rainwater, groundwater, or plumbing water leaks 

• Rot or decay in framing 

• Insect and pest damage and activity.
30 

Deficiencies or hazards must be remediated before the project begins, or remediation must be 

incorporated into the scope of the project. 

Identify any atmospherically vented (or naturally aspirated) combustion appliances in the home. 

With the exception of gas stoves and cooktops, combustion appliances—including fireplaces—

should be direct-vented or direct exhaust-vented equipment. Atmospherically vented appliances 

must be replaced or reconfigured to direct-vented or direct exhaust-vented operation prior to or 

as part of the project.

Verify that all kitchen and bathroom exhausts are 

vented to the exterior of the building. Source control 

ventilation deficiencies must be corrected either prior 

to or as part of the project.

If the home lacks a ventilation system meeting the 

requirements of 2012 IRC, Section M1507.3, a 

ventilation system meeting this requirement must be 

installed either prior to or as part of the project.

4.1.4 Implementation Risks

Construction and renovation work entails inherent 

risks to workers. All applicable safety procedures 

must be followed. 

Implementation risks specific to mineral fiber 

insulation board retrofit derive from the fibrous 

nature of the material. It is recommended that all 

workers handling or cutting material: 

1. Wear protective clothing and avoid exposed 

skin. 

2. Wear goggles or similar enclosed eye protection.

3. Wear gloves that are impermeable to fibers.

4. Use tight-fitting dust masks to provide appropriate protection from airborne fibers. 

5. Refer to material safety data sheets and manufacturer instructions for safe handling and 

exposure. 

4.1.5 Installation Procedure

1. Remove existing cladding and prepare the roof sheathing to receive the air and water 

control membrane. 

Removal of roof cladding is a well-established procedure.

Appropriate preparation of the roof sheathing will depend upon the nature of the existing 

sheathing and the air control strategy pursued. If a sheet good is used as the air and water control 

Ensuring Success

Significant retrofit of building enclosure 

components will change the dynamics of 

water, air, vapor, and heat flow within 

the home. To ensure that these 

changing dynamics do not have 

negative ramifications for health and 

safety or for building durability, the 

following conditions must be met either 

prior to or as part of the project.

• Combustion safety—All non-cooking 

appliances, including fireplaces, must 

be direct-vented or direct exhaustvented appliances.

• Ventilation—Whole-house ventilation 

meeting the requirements of 2012 

IRC, Section M1507.3 is installed and 

operational.

The following is also recommended:

• Soil gas control system—An active or 

passive soil gas control system is 

installed and operational.
31 

layer, all protruding fasteners must be removed to avoid punctures or tears in the membrane. 

Gaps or voids in the sheathing layer may need to be in filled. Use a primer for self-adhered 

membranes if recommended by the membrane manufacturer.

1a. Chainsaw retrofit: Remove roof overhangs. 

If roof framing allows, remove roof sheathing, rafter tails, and gable rake framing to flush with 

the exterior wall sheathing. Provide structural sheathing infill and/or blocking as needed to allow 

wall sheathing plane to meet roof sheathing plane. 

2. Install an air and water control membrane. 

Install a continuous water and air control membrane. 

OR

Tape the wood panel sheathing with flashing tape (acrylic or bituminous adhesive) to form a 

continuous air control membrane (see Figure 6) and install a water control membrane over the 

wood panel sheathing (see Figures 7 and 8). 

Connect the air control membrane to the air control layer of adjacent assemblies in an airtight 

and durable manner (see Figures 7 and 8). Seal all penetrations against air and water leaks. 

The air and water control membrane or water control membrane must provide vapor control as 

required: class II (or lower) in hot humid climates, class III (or lower) elsewhere. See Section 3. 

Figure 6. Taped wood panel roof sheathing as air control membrane
32 

Figure 7. “Chainsaw” transition of air and water control membrane

Figure 8. “Chainsaw” transition of air and water control membrane at rake

3. Install a mineral fiber insulation board. 

Install over the air and water control membrane. Butt joints tight. When installing multiple 

layers, offset seams in two directions.

3a. Chainsaw retrofit: Install framing for new overhangs. 

Install framing for new roof overhangs over continuous insulation board. Many contractors who 

have experience with “chainsaw” retrofits prefer to pre-assemble framing for new roof overhangs 

(see Figure 9). 
33 

Figure 9. Pre-assembled insulated roof overhang framing being

lifted into place at a gable rake for a “chainsaw” retrofit

3b. Vented roof option: Install purlins for ventilation and attachment or roof sheathing. 

For a vented roof, install 2 × 4 on the flat purlins over the insulation board and fasten through the 

insulation board to the roof structure. Purlins need not be continuous from the eave to the ridge. 

Breaks in the purlins can allow for cross-ventilation as would facilitate ventilation of complex 

roofs involving hips, valleys or interruptions such as dormers and skylights. A structural 

engineer should be consulted for sheathing/purlin attachment type and number used, because it 

will be based on wind loads and potential uplift. 

4. Install roof sheathing/cladding. 

Install roof sheathing to serve as a nail base for roof cladding (e.g., shingles). Attach the 

sheathing to the roof structure through insulation board. 

In the vented roof approach, attach the roof sheathing to purlins. 

5. Install roof cladding and flashing. 

Install underlayment, ice and water membrane, flashings, and roofing per new construction best 

practices.

6. Install rafter cavity insulation. 

Install insulation in framing cavities to the underside of the existing roof deck. Refer to Table 8 

and calculated ratios to ensure that the level of insulation does not upset the ability of the exterior 

insulation to provide condensation control. 

See Figure 10 through Figure 17 for details about this procedure. 
34 

4.1.6 High Performance Mineral Fiber Retrofit Details

Figure 10. Schematic detail for “chainsaw” eave transition from a high performance

mineral fiber retrofit roof assembly to a high performance mineral fiber retrofit wall assembly
35 

Figure 11. Schematic detail for non-“chainsaw” eave transition from a high performance

mineral fiber retrofit roof assembly to a high performance mineral fiber retrofit wall assembly
36 

Figure 12. Schematic detail for “chainsaw” gable rake transition from a high performance

mineral fiber retrofit roof assembly to a high performance mineral fiber retrofit wall assembly
37 

Figure 13. Schematic detail for “chainsaw” eave transition from a high performance

mineral fiber retrofit roof assembly to a non-retrofit wall assembly
38 

Figure 14. Schematic detail for non-“chainsaw” eave transition from a high performance

mineral fiber retrofit roof assembly to a non-retrofit wall assembly
39 

Figure 15. Schematic detail for “chainsaw” gable rake transition from a high performance

mineral fiber retrofit roof assembly to a non-retrofit wall assembly
40 

Figure 16. Schematic detail for transition from a lower high performance mineral fiber

retrofit roof assembly to a high performance mineral fiber retrofit wall assembly
41 

Figure 17. Schematic detail for transition from a lower high performance mineral fiber

retrofit roof assembly to a non-retrofit wall assembly

4.2 High Performance Mineral Fiber Retrofit Wall Assembly

4.2.1 Scope of Work

1. Remove wall cladding and trim. Prepare the wall sheathing for the water and air control 

membrane. 

2. Remove windows and doors as needed to allow flashing of openings and air control 

transitions into openings. 
42 

3. Install a continuous water and air control membrane over the wall sheathing to provide 

vapor control in accordance with code. Transition the wall air and water control 

membrane to adjacent assemblies.

4. Install flashings and air control transitions.

5. Reinstall windows and doors or install new windows and doors in properly flashed 

openings. 

6. Install mineral fiber insulation board in accordance with code to satisfy the high R-value 

performance target for the assembly and for adequate condensation control (the higher Rvalue requirement shall govern). 

7. Install furring strips over insulation board and attached to structure through insulation 

board. Install furring strips in a vertical orientation only. 

8. Install wall cladding and trim. Attach to furring strips.

4.2.2 Climate-Specific Factors

In hot-humid climates, the air and water control membrane between the mineral fiber insulation 

board and the roof/wall sheathing must be a class II (or lower) vapor retarder.

4.2.3 Field Inspection

Identify and address risks to occupants or the building that could be aggravated by the work. 

Verify safe working conditions. Determine whether the building has more urgent problems that 

must be addressed. Determine the feasibility of the retrofit solution and of options. 

Inspect and assess the building for:

• Structural integrity of the frame and foundation 

• Safety and serviceability of the electrical system

• Presence of hazardous materials (e.g., lead, radon, asbestos) 

• Rainwater, groundwater, or plumbing water leaks 

• Rot or decay in framing 

• Insect and pest damage and activity.

Deficiencies or hazards must be remediated prior to or as part of the project. 

Identify any atmospherically vented (or naturally aspirated) combustion appliances in the home. 

With the exception of gas stoves and cooktops, combustion appliances—including fireplaces—

should be direct-vented or direct exhaust-vented equipment. Atmospherically vented appliances 

must be replaced or reconfigured to direct-vented or direct exhaust-vented operation prior to or 

as part of the project.

Verify that all kitchen and bathroom exhausts are vented to the exterior of the building. Source 

control ventilation deficiencies must be corrected either prior to or as part of the project.
43 

If the home lacks a ventilation system meeting the requirements of 2012 IRC, Section M1507.3, 

a ventilation system meeting this requirement must be installed either prior to or as part of the 

project.

4.2.4 Implementation Risks

Construction and renovation work entails inherent risks to workers. All applicable safety 

procedures must be followed. 

Implementation risks specific to mineral fiber insulation board retrofit derive from the fibrous 

nature of the material. It is recommended that all

workers handling or cutting material: 

1. Wear protective clothing and avoid exposed 

skin. 

2. Wear goggles or similar enclosed eye 

protection. 

3. Wear gloves that are impermeable to fibers.

4. Use tight-fitting dust masks to provide 

appropriate protection from airborne fibers.

5. Refer to material safety data sheets and 

manufacturer instructions for safe handling and 

exposure. 

4.2.5 Installation Procedure

1. Remove existing cladding and trim. Prepare the 

wall sheathing to receive the air and water 

control membrane.

Removal of siding and trim is a well-established 

procedure. Also remove decking that is adjacent to the 

exterior wall as needed to allow for continuous 

insulation of the wall.

Appropriate preparation of the wall sheathing will depend upon the nature of the existing 

sheathing and the air control strategy pursued. If a sheet good is used as the air and water control 

layer, all protruding fasteners must be removed to avoid punctures or tears in the membrane. 

Gaps or voids in the sheathing layer may need to be in filled. Use a primer for self-adhered 

membranes if recommended by the membrane manufacturer.

2. Remove windows and doors. 

Typically, the windows and doors will need to be removed to allow proper flashing of the 

window and door openings and to permit the installation of air control transition membranes. 

Ensuring Success 

Significant retrofit of building 

enclosure components will change the 

dynamics of water, air, vapor, and 

heat flow within the home. To ensure 

that these changing dynamics do not 

have negative ramifications for health 

and safety or for building durability, 

the follow conditions below must be 

met either prior to or as part of the 

project.

• Combustion safety—All noncooking appliances, including 

fireplaces, direct-vented or direct 

exhaust-vented appliances.

• Ventilation—Whole-house 

ventilation meeting the 

requirements of 2012 IRC, Section 

M1507.3 is installed and 

operational.

The following is also recommended:

• Soil gas control system—An active 

or passive soil gas control system 

installed and operational.
44 

3. Install and implement air and water control membrane. 

Install a continuous water and air control membrane. 

OR

Tape the wood panel sheathing with flashing tape (acrylic or bituminous adhesive) to form a 

continuous air control membrane and install a water control membrane over the wood panel 

sheathing. 

Connect the air control membrane to the air control layer of adjacent assemblies in an airtight 

and durable manner. Seal all penetrations against air and water leaks. 

The water and air control membrane or water control membrane must provide vapor control as 

required: class II (or lower) in hot humid climates, class III (or lower) elsewhere. See Section 3. 

4. Install flashings and air control transitions. 

Transition the air control into window and door rough openings and air seal all penetrations 

through the wall. Flash window and door rough openings as well as all wall penetrations. 

5. Install windows and doors. 

Reinstall windows and doors or install new windows and doors in properly flashed openings. Air 

seal window and door units to the air control transition membranes at the interior perimeters of 

window and door units. 

6. Install mineral fiber insulation board. 

Install over the air and water control membrane. Butt joints tight. When installing multiple 

layers, offset seams in two directions. Until furring strips are installed, mineral fiber insulation 

board pieces can be held in place with cap nails or screws with roofing washers.

7. Install furring strips. 

Install furring strips over insulation board and attached furring strips to the wall structure through 

the insulation board. Install furring strips in a vertical orientation only. It is important to install 

furring strips in a vertical orientation only to allow drainage from behind the cladding/trim and to 

prevent water from dwelling within the system. With mineral fiber insulation board 1 × 4 furring 

is recommended. The furring need not be preservative treated for moisture protection. 

The spacing of fasteners through the furring strips must be such that the cladding load is 

distributed to no more than 10 lb per fastener. 

8. Install cladding and trim. 

Attach the wall cladding and trim to the vertical furring strips.

See Figure 18 through Figure 31 for details about this procedure. 
45 

4.2.6 High Performance Mineral Fiber Retrofit Details

Figure 18. Schematic detail for “chainsaw” eave transition from a high performance

mineral fiber retrofit roof assembly to a high performance mineral fiber retrofit wall assembly
46 

Figure 19. Schematic detail for non-“chainsaw” eave transition from a high performance

mineral fiber retrofit roof assembly to a high performance mineral fiber retrofit wall assembly
47 

Figure 20. Schematic detail for “chainsaw” gable rake transition from a high performance

mineral fiber retrofit roof assembly to a high performance mineral fiber retrofit wall assembly
48 

Figure 21. Schematic detail for eave transition from a high performance mineral fiber

retrofit wall assembly to a non-retrofit roof assembly
49 

Figure 22. Schematic detail for gable/rake transition from a high performance mineral fiber

retrofit wall assembly to a non-retrofit roof assembly
50 

Figure 23. Schematic detail for transition from a lower high performance mineral fiber

retrofit roof assembly to a high performance mineral fiber retrofit wall assembly
51 

Figure 24. Schematic detail for transition from a high performance mineral fiber

retrofit wall assembly to an insulated lower roof assembly
52 

Figure 25. Schematic detail for transition from a high performance mineral fiber

retrofit wall assembly to an existing lower attic
53 

Figure 26. Schematic detail for transition from a high performance mineral fiber

retrofit wall assembly to a porch roof
54 

Figure 27. Schematic detail for transition from a high performance mineral fiber

retrofit wall assembly to an attached deck in a field of wall
55 

Figure 28. Schematic detail for transition from a high performance mineral fiber

retrofit wall assembly to an attached deck at base of wall
56 

Figure 29. Schematic detail for transition from a high performance mineral fiber retrofit

wall assembly to a top of high performance mineral fiber retrofit foundation wall assembly
57 

Figure 30. Schematic detail for transition from a high performance mineral fiber retrofit

wall assembly to a flat-surface foundation wall without exterior retrofit
58 

Figure 31. Schematic detail for transition from a high performance mineral fiber retrofit

wall assembly to a bumpy-surface foundation wall

Figure 32 through Figure 43 show the installation of a new window or the reinstallation of a 

window in the high performance mineral fiber retrofit wall assembly. The schematic details 

include schematics for the head, jamb, and sill of the window opening. The sequence illustrations 

demonstrate (1) installation of a window in a wall assembly using a non-adhered sheet good 

water and air control membrane; and (2) installation of the exterior trim extension. The window 

installation sequence for a fully adhered or liquid-applied water and air control membrane is 

slightly different in how the head flashing is integrated into the water and air control membrane. 
59 

The trim installation sequence is applicable to situations where the existing window is left in 

place.

Figure 32. Schematic detail for window head of new window or

reinstalled window in a high performance mineral fiber retrofit wall assembly
60 

Figure 33. Schematic detail for window jamb of new window or

reinstalled window in a high performance mineral fiber retrofit wall assembly
61 

Figure 34. Schematic detail for window sill of new window or

reinstalled window in a high performance mineral fiber retrofit wall assembly
62 

Figure 35. Steps 1 and 2 of installation sequence for new window or

reinstalled window in a high performance mineral fiber retrofit wall assembly
63 

Figure 36. Steps 3 and 4 of installation sequence for new window or

reinstalled window in a high performance mineral fiber retrofit wall assembly
64 

Figure 37. Steps 5 and 6 of installation sequence for new window or

reinstalled window in a high performance mineral fiber retrofit wall assembly
65 

Figure 38. Steps 7 and 8 of installation sequence for new window or

reinstalled window in a high performance mineral fiber retrofit wall assembly
66 

Figure 39. Steps 9 and 10 of installation sequence for new window or reinstalled window in

a high performance mineral fiber retrofit wall assembly
67 

Figure 40. Steps 1 and 2 of exterior trim installation sequence for

window in a high performance mineral fiber retrofit wall assembly
68 

Figure 41. Steps 3 and 4 of exterior trim installation sequence for

window in a high performance mineral fiber retrofit wall assembly
69 

Figure 42. Steps 5 and 6 of exterior trim installation sequence for

window in a high performance mineral fiber retrofit wall assembly
70 

Figure 43. Step 7 of exterior trim installation sequence for window in

a high performance mineral fiber retrofit wall assembly

Figure 42 through Figure 46 show the implementation of the high performance mineral fiber 

retrofit wall assembly at a window opening where the existing window is to remain in place. 

There may be many reasons for leaving an existing window in place; however, this prevents the 

contractor from ensuring that the window opening is properly flashed. The air control and water 

control transitions around a window that remains in place are not as robust as for a window 

opening that can be flashed and lined as part of the retrofit project. The exterior trim sequence 

illustrated above is applicable to this condition. 
71 

Figure 44. Schematic detail for window head of an existing window remaining

in place in a high performance mineral fiber retrofit wall assembly
72 

Figure 45. Schematic detail for window jamb of an existing window remaining

in place in a high performance mineral fiber retrofit wall assembly
73 

Figure 46. Schematic detail for window sill of an existing window remaining

in place in a high performance mineral fiber retrofit wall assembly

Figure 47 through Figure 59 show the installation of a new door or the reinstallation of a door in 

the high performance mineral fiber retrofit wall assembly. 
74 

Figure 47. Schematic detail for door head of new door or reinstalled door

in a high performance mineral fiber retrofit wall assembly

Note: See installation sequence for new door or reinstalled door in a high performance mineral fiber retrofit wall 

assembly for flashing installation details.
75 

Figure 48. Schematic detail for door jamb of new door or reinstalled door

in a high performance mineral fiber retrofit wall assembly
76 

Figure 49. Schematic detail for door sill of new door or reinstalled door

in a high performance mineral fiber retrofit wall assembly
77 

Figure 50. Steps 1 and 2 of installation sequence for new door or

reinstalled door in a high performance mineral fiber retrofit wall assembly
78 

Figure 51. Steps 3 and 4 of installation sequence for new door or

reinstalled door in a high performance mineral fiber retrofit wall assembly 
79 

Figure 52. Steps 5 and 6 of installation sequence for new door or

reinstalled door in a high performance mineral fiber retrofit wall assembly
80 

Figure 53. Steps 7 and 8 of installation sequence for new door or

reinstalled door in a high performance mineral fiber retrofit wall assembly
81 

Figure 54. Steps 9 and 10 of installation sequence for new door or

reinstalled door in a high performance mineral fiber retrofit wall assembly
82 

Figure 55. Steps 11 and 12 of installation sequence for new door or

reinstalled door in a high performance mineral fiber retrofit wall assembly
83 

Figure 56. Steps 1 and 2 of exterior trim installation sequence for door

in a high performance mineral fiber retrofit wall assembly
84 

Figure 57. Steps 3 and 4 of exterior trim installation sequence for door

in a high performance mineral fiber retrofit wall assembly
85 

Figure 58. Steps 5 and 6 of exterior trim installation sequence for door 

in a high performance mineral fiber retrofit wall assembly
86 

Figure 59. Step 7 of exterior trim installation sequence for door 

in a high performance mineral fiber retrofit wall assembly

Figure 60 through Figure 67 show the treatment of typical wall penetrations through the high 

performance mineral fiber retrofit wall assembly.
87 

Figure 60. Schematic plan (above) and section (below) details for wire penetration

and fixture mount in a high performance mineral fiber retrofit wall assembly
88 

Figure 61. Schematic plan and section details for wire penetration and exterior

outlet box mount in a high performance mineral fiber retrofit wall assembly
89 

Figure 62. Schematic plan and section details for duct penetration and vent

hood trim mount in a high performance mineral fiber retrofit wall assembly
90 

Figure 63. Steps 1 and 2 of sequence for treatment of duct/pipe penetration

through a high performance mineral fiber retrofit wall assembly
91 

Figure 64. Steps 3 and 4 of sequence for treatment of duct/pipe penetration

through a high performance mineral fiber retrofit wall assembly
92 

Figure 65. Steps 5 and 6 of sequence for treatment of duct/pipe penetration

through a high performance mineral fiber retrofit wall assembly
93 

Figure 66. Steps 7 and 8 of sequence for treatment of duct/pipe penetration

through a high performance mineral fiber retrofit wall assembly
94 

Figure 67. Step 9 of sequence for treatment of duct/pipe penetration

through a high performance mineral fiber retrofit wall assembly

4.3 High Performance Mineral Fiber Retrofit Foundation Wall Assembly

4.3.1 Scope of Work

1. Locate underground utilities and implement measures to ensure their protection. Verify 

safe conditions for perimeter excavation. 

2. Excavate the foundation perimeter to a depth and width required to implement the wall 

retrofit and foundation skirt measures. Install clean aggregate for insulated foundation 

skirt. Grade bottom of excavation to slope at least 5% away from foundation. 

3. Install metal closure/transition flashing at top of foundation wall. 

4. Install non-moisture-sensitive rigid insulation at bottom of excavation as required. 

5. Install ground roof/foundation skirt and secure high end to foundation with retaining bar. 

6. Install drainpipe at low end of ground roof/foundation skirt. Slope to daylight outlet or 

storm water collection. DO NOT connect drainpipe to foundation drain. 

7. Install mineral fiber insulation board with protective finish to the exterior of the 

foundation wall.

8. Backfill excavation to within 4 in. of finished grade with free-draining backfill.

9. Install a drip trench adjacent to foundation wall and separated from backfill/soil with a 

durable filter fabric.

4.3.2 Climate-Specific Factors

In climate zone 5 and above, the ground roof/foundation skirt for a slab-on-grade foundation 

should be insulated. The ground roof/foundation skirt should be insulated in climate zone 2 and 
95 

above if the home has a crawlspace or basement. The level of recommended insulation is as 

follows: 

• R-5 in climate zone 2 

• R-7.5 in climate zones 3 and 4 

• R-10 minimum in climate zones 5 and 6 

• R-15 minimum in climate zone 7 

• R-20 minimum in climate zone 8. 

The insulation used must be approved for below-grade applications (e.g., XPS or foamed glass) 

and placed over a capillary break consisting of a sloped bed of clean aggregate. 

4.3.3 Field Inspection

Identify and address risks to occupants or the building that could be aggravated by the work. 

Verify safe working conditions. Determine whether the building has more urgent problems that 

must be addressed. Determine the feasibility of the retrofit solution and of options. 

Inspect and assess the building for:

• Structural integrity of the frame and foundation 

• Contaminated soil (e.g., with lead, pesticides) surrounding the foundation 

• Safety and serviceability of the electrical system

• Hazardous materials (e.g., lead, radon asbestos) in or on the building 

• Rainwater, groundwater, or plumbing water leaks 

• Rot or decay in framing 

• Insect and pest damage and activity.

Deficiencies or hazards must be remediated prior to or as part of the project. 

Locate any underground utilities (electric, gas, water, sewer) serving the building or passing near 

the foundation. Ensure these are protected during the retrofit project.

Identify any atmospherically vented (or naturally aspirated) combustion appliances in the home. 

With the exception of gas stoves and cooktops, combustion appliances—including fireplaces—

should be direct-vented or direct exhaust-vented equipment. Atmospherically vented appliances 

must be replaced or reconfigured to direct-vented or direct exhaust-vented operation prior to or 

as part of the project.

Verify that all kitchen and bathroom exhausts are vented to the exterior of the building. Source 

control ventilation deficiencies must be corrected either prior to or as part of the project.
96 

If the home lacks a ventilation system meeting the requirements of 2012 IRC, Section M1507.3, 

a ventilation system meeting this requirement must be installed either prior to or as part of the 

project.

4.3.4 Implementation Risks

Construction and renovation work entails inherent risks to 

workers. All applicable safety procedures must be 

followed. 

Implementation risks specific to mineral fiber insulation 

board retrofit derive from the fibrous nature of the 

material. All workers handling or cutting material should: 

1. Wear protective clothing and avoid exposed skin. 

2. Wear goggles or similar enclosed eye protection.

3. Wear gloves that are impermeable to fibers.

4. Use tight-fitting dust masks to provide appropriate 

protection from airborne fibers.

5. Refer to material safety data sheets and 

manufacturer instructions for safe handling and 

exposure. 

4.3.5 Installation Procedure

0. Locate underground utilities. Ensure these are 

protected throughout the project.

Locate utilities serving the building or passing near the foundation. Implement measures to 

protect these throughout the project.

STOP! Do not proceed if underground utilities are not located. 

1. Excavate the perimeter.

Excavate to a depth of at least 2 ft below grade and 4 ft from the foundation wall. The bottom of 

excavation must slope at least 5% away from the foundation. For an insulated ground 

roof/foundation skirt, the depth of the excavation must also accommodate a clean aggregate layer 

and the insulation thickness.

The base of the excavation furthest from the foundation should be shaped and graded to allow 

the ground roofing material to form a trough for the drainpipe that is sloped to the drain outlet.

2. Install a metal closure and transition flashing. 

Install a continuous metal closure and transition flashing at the top of the foundation wall. This

must be sealed to the foundation wall with bituminous flashing membrane and sealant. Use 

Ensuring Success

Significant retrofit of building 

enclosure components will change the 

dynamics of water, air, vapor, and 

heat flow within the home. To ensure 

that these changing dynamics do not 

have negative ramifications for health 

and safety or for building durability, 

the following conditions must be met 

either prior to or as part of the project. 

• Combustion safety—All noncooking appliances, including 

fireplaces, direct-vented or direct 

exhaust-vented appliances.

• Ventilation—Whole-house 

ventilation meeting the 

requirements of 2012 IRC, Section 

M1507.3 is installed and 

operational.

The following is also recommended:

• Soil gas control system—An active 

or passive soil gas control system 

installed and operational.
97 

primer to ensure robust adhesion of bituminous flashing membrane. Seal lapped seams in the 

metal closure and transition flashing with bituminous membrane flashing or bituminous sealant. 

3. Install an insulated ground roof/foundation skirt. 

Where an insulated ground roof/foundation skirt is recommended or otherwise desired, place a 

capillary break of clean aggregate at the bottom of the excavation. Ensure that the surface of the 

aggregate slopes away from the foundation at 5% minimum. Place rigid insulation board over the 

aggregate and extending from the foundation wall to at least 3 ft from the foundation wall. The 

rigid insulation can be temporarily held in place with stakes at the bottom edge of the insulation 

boards. 

The insulation material used in this application must be a rigid insulation board that is nonmoisture sensitive. XPS and foamed glass rigid insulation meet these requirements. Even with 

the non-moisture-sensitive insulation material, it is important to provide capillary protection 

because sustained exposure to ground moisture could lead to moisture absorption and 

degradation in the insulation. 

4. Install rubber roofing.

Place rubber roofing or similar material across the bottom of the excavation or on top of the rigid 

insulation and secure to the foundation with a retaining bar. Seams in the roofing material should 

be lapped at least 8 in. 

5. Install a drainpipe. 

Install a perforated drainpipe at the low end of the ground roof/foundation skirt. Slope the 

drainpipe to a storm water collection system or to a daylight outlet. Wrap the drainpipe in clean 

aggregate and filter fabric.

6. Install mineral fiber insulation board. 

Install mineral fiber insulation board in multiple layers to a thickness as required to meet the 

thermal performance target for the foundation wall. The first layer installed against the 

foundation wall should be continuous with joints between insulation board pieces butted tight. 

Furring strips of plastic or preservative material (e.g., 1 in. decking ripped to width) is installed 

over the continuous insulation layer. Furring strips are fastened to the foundation wall using 

masonry fasteners. Mineral fiber insulation board with a thickness matching that of the furring 

strips is in filled between the furring strips. Additional layers of mineral fiber insulation board 

can be installed over the furring strip layer as needed or desired. 

7. Install a protective finish. 

Install an impact-resistant, non-ultraviolet-sensitive, non-moisture-sensitive finish over the 

mineral fiber insulation board from the top of the insulation to the level of finished grade. 

Examples of suitable protective finishes include brake-formed aluminum coil stock and cement 

stucco parge coat over cement backer board. The protective finish can be fastened to the furring 

inset in the second layer of mineral fiber insulation board. 
98 

The mineral fiber exterior foundation insulation does not need to be protected below grade. 

Certain protective finish materials such as stucco are not appropriate for ground contact and, 

therefore, are best terminated within the thickness of the drip trench and above the top of the 

backfill material.

8. Backfill with free-draining material. 

The excavation should be backfilled to within 4 in. of finished grade with free-draining material. 

Separate free draining material from the soil with filter fabric.

9. Install a drip trench and finished grade. 

Install a drip trench of clean stone that extends from the foundation wall finish past the drip line 

of the roof. The drip trench should be separated from the surrounding soil and backfill with 

landscape edging (at the side) and durable filter fabric. The drip trench serves two important 

functions: (1) it serves as a capillary break between the soil and the above-grade foundation 

retrofit assembly; and (2) it dissipates the energy of falling rain or roof runoff, thereby limiting 

splash-back. The drip trench may also serve an aesthetic landscape design purpose.

Finished grade should be sloped away from the foundation at a 5% or greater slope. 
99 

4.3.6 High Performance Mineral Fiber Retrofit Details

Figure 68. Schematic detail for insulated ground roof/foundation skirt with

a high performance mineral fiber retrofit foundation wall assembly
100 

Figure 69. Schematic detail for transition from a high performance mineral fiber retrofit wall 

assembly to a top of high performance mineral fiber retrofit foundation wall assembly showing 

how the metal closure/transition flashing is secured and sealed to the foundation wall.
101 

Figure 70. Schematic detail for transition from a non-retrofit wall assembly to a top of high 

performance mineral fiber retrofit foundation wall assembly showing how the metal 

closure/transition flashing is secured and sealed to the foundation wall.
102 

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DOE/GO-102015-4555 ▪ January 2015