Evaluating an Exterior 

Insulation and Finish System 

for Deep Energy Retrofits

Jordan Dentz and David Podorson 

Advanced Residential Integrated Energy 

Solutions Collaborative

January 2014
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iii

Evaluating an Exterior Insulation and Finish System 

for Deep Energy Retrofits

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:

ARIES Collaborative 

The Levy Partnership, Inc.

1776 Broadway, Suite 2205 

New York, NY 10019 

NREL Technical Monitor: Michael Gestwick

Prepared under Subcontract No. KNDJ-0-40347-03

January 2014 
iv

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v 

Contents

List of Figures ............................................................................................................................................ vi

List of Tables .............................................................................................................................................. vi

Definitions.................................................................................................................................................. vii

Acknowledgments ................................................................................................................................... viii

Executive Summary................................................................................................................................... ix

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

1.1 Research Questions ..............................................................................................................2

1.2 Relevance to Building America Goals .................................................................................2

2 Background........................................................................................................................................... 3

3 Field Study ............................................................................................................................................ 6

3.1 Approach ..............................................................................................................................6

3.2 Case Study Site ....................................................................................................................6

3.3 Exterior Insulation and Finish System Application .............................................................6

4 Modeling.............................................................................................................................................. 12

5 Discussion........................................................................................................................................... 18

5.1 Site and Safety Risks .........................................................................................................18

5.2 Installation Risks ................................................................................................................18

5.3 Code and Regulatory Issues ...............................................................................................18

5.4 Trade Resources .................................................................................................................19

5.5 Maintenance .......................................................................................................................19

5.6 Durability and Reliability ..................................................................................................19

5.7 Occupant Comfort, Health, and Safety ..............................................................................19

5.8 System Interactions—Enclosure ........................................................................................19

5.9 System Interactions—Equipment ......................................................................................20

5.10 Application Alternatives ........................................................................................20

5.10.1 Waterproofing ........................................................................................................20

5.10.2 Finishes ..................................................................................................................21

5.10.3 Fabrication .............................................................................................................21

5.10.4 Thickness ...............................................................................................................21

5.11 Cost ........................................................................................................................21

5.12 Energy Efficiency ..................................................................................................22

6 Conclusions ........................................................................................................................................ 23

References................................................................................................................................................. 24

Appendix A Construction Details............................................................................................................ 26
vi 

List of Figures

Figure 1. Typical lightweight EIFS wall panel .......................................................................................... 4

Figure 2. Field-applied EIFS showing yellow water resistive barrier, white EPS insulation with 

yellow reinforcing mesh, and gray basecoat in foreground ............................................................ 5

Figure 3. Front and rear elevations of the pre-retrofit home.................................................................. 6

Figure 4. After scaffolding is set up a bottom track is attached to the base of the sheathing to 

accept the bottom of the EIFS system. .............................................................................................. 7

Figure 5. A liquid water resistive coating is brushed onto the sheathing; a layer of reinforcing 

mesh is embedded into the coating at the sheathing joints............................................................ 7

Figure 6. After the coating is complete, more reinforcing mesh affixed around the newly installed 

windows; it will be used to wrap the edges of the insulation.......................................................... 8

Figure 7. Sections of EPS insulation, 4 in. thick and measuring 2 ft × 4 ft are adhered to the walls. 

Where necessary the backside of the panels are rasped to conform to irregularities in the 

substrate wall. The EPS joints are smoothed out. ............................................................................ 8

Figure 8. EPS panels are placed around the new windows; an additional 1-in. thick by 4-in. wide 

layer of EPS is used to form window trim. Other applied shapes can be used to create 

architectural forms as desired. ........................................................................................................... 9

Figure 9. The gray basecoat is troweled on over an embedded layer of reinforcing mesh................ 9

Figure 10. The basecoat is applied over the formed window trim and edges of the EPS panels, 

embedding the yellow mesh around windows and other penetrations.......................................... 9

Figure 11. The finish coat is mixed and applied with trowels. ............................................................. 10

Figure 12. The finished system ............................................................................................................... 10

Figure 13. BEopt modeled source energy savings and utility bill savings— Islip, New York; climate 

zone 4................................................................................................................................................... 13

Figure 14. BEopt optimization curve with midrange vinyl siding reference (Islip, New York).......... 14

Figure 15. BEopt optimization curve with high-end vinyl siding reference (Islip, New York)........... 15

Figure 16. BEopt modeled source energy savings and utility bill savings (Boston)......................... 16

Figure 17. BEopt optimization curve with midrange vinyl siding reference (Boston)....................... 16

Figure 18. BEopt optimization curve with high-end vinyl siding reference (Boston)........................ 17

Figure 19. Eave detail. The existing eave was removed. ...................................................................... 26

Figure 20. Detail at porch roof. A 2-in. gap is left between at the bottom of the upper wall EIFS.... 27

Figure 21. Detail at foundation ................................................................................................................ 28

Figure 22. Detail at window head. The water resistive barrier ties into the window flashing. (figure 

adapted from Fusion Architects) ...................................................................................................... 29

Figure 23. Detail at window sill................................................................................................................ 30

Figure 24. Detail at rake............................................................................................................................ 31

Unless otherwise indicated, all figures were created by ARIES. 

List of Tables

Table 1. Case Study Home Characteristics.............................................................................................. 6

Table 2. Labor Breakdown ....................................................................................................................... 11

Table 3. Modeled House Characteristics ................................................................................................ 12

Table 4. Optimization Options ................................................................................................................. 14

Table 5. Optimization Modeling Assumptions ....................................................................................... 15

Table 6. Case Study Site Costs ............................................................................................................... 22

Unless otherwise indicated, all tables were created by ARIES. 
vii 

Definitions

ARIES Advanced Residential Integrated Energy Solutions 

Collaborative Building America team

BEoptTM Building Energy Optimization program

CO2 Carbon dioxide

EIFS Exterior insulation and finish system

EPS Expanded polystyrene

HVAC Heating, ventilation, and air conditioning

NYSERDA New York State Energy Research and Development Authority

XPS Extruded polystyrene
viii

Acknowledgments

The authors wish to acknowledge the assistance and support of Rick Wertheim and Stephen 

Muzyka from United Way of Long Island, J.P. Lardoux of Fusion Architecture, PLLC, George 

Etts of Performance Contracting of Long Island, Daniel Canova and John Edgar of Sto

Corporation, and Sto applicators Colm Freehill and Martin Darcy of D.N.F. Wall Systems, Inc. 

The authors also wish to recognize the guidance provided by Robert Carver and Greg Pedrick of 

New York State Energy Research and Development Authority, and Michael Gestwick of the 

National Renewable Energy Laboratory. 
ix

Executive Summary

The expression deep energy retrofit lacks precision but broadly suggests a program of existing 

building improvement that has as one its goals a dramatic improvement in the level of energy 

efficiency while providing a healthier living environment and improving durability and safety. 

Adding insulation to exterior walls is often a key piece of a deep energy retrofit. However, this 

measure is often cost prohibitive and there are formidable challenges to altering the thermal 

envelope of existing, older structures. This report provides a case study of a deep energy retrofit 

using a site-applied exterior insulation and finish system (EIFS). Prefabricated EIFS panels are 

also discussed as a potential wall insulation retrofit solution.

EIFSs are common in new and retrofit commercial construction. Such products typically consist 

of five layers installed over the top of a water resistive barrier as follows: 

1. Adhesive 

2. Foam insulation

3. Base coat

4. Reinforcing mesh embedded in the base coat

5. Top or finish coat. 

They can be applied to new or existing buildings that employ wood or masonry construction, and 

can utilize an insulation thickness of up to 16 in. However, such systems are rarely used in lowrise residential retrofits. Reasons for this might include a lack of demand for or knowledge of the 

systems in residential retrofit industry, high cost, and/or lack of suitable distribution channels 

serving the residential market.

While the final appearance of an EIFS installation resembles stucco, it is a distinctly different 

system. Stucco is a generic cementitious-based material, whereas EIFSs are proprietary synthetic 

formulations distributed by manufacturers to a network of authorized applicators. An EIFS is 

composed of polymeric (organic) bonded aggregate and cement reinforced with a glass mesh. 

Stucco is made of inorganic cement, sand, and lime. 

In this project, a home was retrofitted using a site-applied 4-in.-thick EIFS. Site-specific details 

were developed as required for the residential retrofit application. Site work and the costs of the 

EIFS were documented. 

The case study home was modeled using version 2 of the National Renewable Energy 

Laboratory-developed Building Energy Optimization (BEoptTM) energy and cost analysis 

software. While a package utilizing the 4-in. EIFS is the optimal retrofit of the options analyzed 

in terms of annualized energy-related costs, it is higher cost than replacing the siding with 

midrange vinyl alone. However, compared to high-end vinyl, the EIFS package has a lower 

annualized energy cost. This held true for both the Islip, New York (climate zone 4) and Boston 

(climate zone 5) case studies. 

The report discusses the risks, selection criteria, interactions with other building systems, cost, 

performance, and other aspects of using an EIFS in a deep energy retrofit. EIFSs do not require 
x 

special site safety precautions beyond general construction site precautions. Moisture design is 

important. Trapping moisture between two vapor/air barriers is a risk of all wall systems, 

including EIFS cladding applications if an interior vapor barrier exists and if there is not 

adequate ventilation through the drainage plane behind the insulation layer. Face-sealed 

approaches that rely on exposed sealants do not provide acceptable rain control or durability and 

are very risky. Generally, fire codes permit EIFSs for most building types and conditions.

The costs for the case study project were about $15.50/ft2 of net wall area (not including 

windows and door openings) for a 4-in.-thick EIFS, including the water resistive barrier and a 

standard finish coat. Costs for other insulation thicknesses mainly vary with material costs, 

because the labor does not change significantly. Extrapolated costs for 2-in. and 6-in. thicknesses

are $15 and $16, respectively. BEopt modeling indicates that 4-in. thickness results in lower 

annualized energy-related costs compared to 2-in. and 6-in. thicknesses for a sample retrofit in 

climate zones 4 and 5. The 4-in. system can be cost effective (i.e., have a lower annualized 

energy cost compared to no retrofit) when the existing siding is at the end of its lifetime and the 

alternative is a high-end vinyl siding or similar cost replacement. The literature contains case 

studies of other R-15 to R-20 exterior-applied wall insulation retrofits at costs of $13–$25/ft2. 

The case study project achieved a blower door test result of 2 ACH50. While this is an indication 

of how tight an EIFS home can be, superior construction of the other components, such as the 

foundation, ceiling, and windows, which were impacted by the retrofit, contributed to the low air 

leakage test result compared to the pre-retrofit leakage rate of 15 ACH50. 

Prefabricated EIFS panels are another potential retrofit approach that will be explored in a future 

case study. The possible benefits of panelization include greater speed and schedule reliability 

that can potentially convert to cost savings, less dust and dirt on site that are a result of rasping 

backs of panels to fit on walls for a site-fabricated system, and greater safety because of less time 

on scaffolds and fewer trips around the building. Prefabricated panels may be less costly for 

certain projects under certain conditions, such as in poor weather and/or where site labor costs 

are high or working conditions difficult. Prefabricated panels can be delivered to the site for 

approximately $7–$9/ft2 (net panel area). If proficient applicators can install the water resistive 

barrier and panels for under $6/ft2

, then off-site panelization becomes a viable alternative to siteapplied systems. Another case study using an off-site panelized EIFS is in progress. 
1 

1 Introduction

Interest in sustainability and carbon emission reductions are driving an interest in higher levels of 

energy efficiency for new and existing buildings. Performance of the building envelope is clearly 

critical in this endeavor. Whole-wall R-values of about R-30 (Aldrich, Arena, & Zoller, 2010) to 

R-40 (Building Science Corporation, 2010) (Wilson, 2009) are sometimes cited as targets for 

cold climate new construction or retrofit. High R-value building envelopes reduce energy 

consumption for space heating and cooling, in addition to enhancing thermal comfort for the 

occupants. Exterior insulating sheathings can significantly improve thermal continuity to achieve 

high R-value walls (Straube & Smegal, 2009). Deep energy retrofits of the thermal enclosure 

also can permit downsizing or elimination of space conditioning equipment because of lower 

loads imposed on the home. 

To achieve a true R-30 wall, retrofits that add at least R-15 to exterior walls are generally

required, as most existing homes do not have greater than R-15 walls. Greater values would be 

needed if existing walls have a lower true R-value or if higher final efficiency levels are desired, 

for example in colder climates. Achieving R-15 additional insulation requires an insulation 

thickness of 2–5 in., depending on the material. With exterior insulation of this thickness, the 

issue of trimming around doors and windows and other details becomes a barrier, potentially 

increasing costs and complicating the work. As a result, exterior wall insulation upgrades at the 

levels required for a deep energy retrofit are often costly. In addition, they can be time 

consuming and disruptive to building occupants. 

This project evaluates, via a case study project and modeling, one approach for exterior wall 

insulation retrofits that holds promise for lowering retrofit costs for certain building types: 

exterior insulation and finish systems.

Exterior insulation and finish systems (EIFSs) are suitable for a variety of existing substrates, 

including wood and masonry. EIFS is most commonly used in commercial construction but can 

be adapted for residential retrofit. Building types for which this alternative may be considered 

include low-rise residential buildings with vinyl or other siding that may need replacement and

the unornamented sides and rears of many masonry structures. For larger, repetitive projects, the 

product can be fabricated offsite into prefinished panels and adhered to the building substrate 

with adhesives, potentially further reducing costs and occupant disruption. 

Costs are a major barrier to mass adoption of any deep energy retrofit solution. Building Science 

Corporation has performed baseline engineering and cost analysis on installing thick layers of 

exterior rigid foam insulation to wood frame and masonry walls (Peter Baker, 2012). The report 

found that insulation up to 1.5 in. thick was cost optimized because above that thickness, 

additional costs for cladding attachment were incurred. Depending on climate zone, insulation 

thicknesses of 4–8 in. were found to be cost neutral compared to replacing cladding only 

(without insulation). 

In a January 2013 report (Jan Kosny, 2013), Fraunhofer CSE estimates costs for various exterior 

wall insulation systems, including vinyl siding over 3-in. extruded polystyrene (XPS) (R-15) at

$13.48/ft2

 and vinyl siding over 5-in. expanded polystyrene (EPS) (R-20) at $13.92/ft2. 
2 

Building Science Corporation reports costs of $14.43/ft2 of wall to retrofit a two-story masonry 

home with exterior insulation and cladding with projected future costs of $12.60/ft2; and 

$25.31/ft2 to retrofit a three-story brick home using a similar system, with estimated future costs 

of $20–$21/ft2 (Neuhauser, 2013). These sources indicate that the cost of exterior wall insulation 

is in the $14/ft2 range for typical single-family homes. This served as a cost target for the EIFS 

case study.

1.1 Research Questions

This research addressed the following questions: 

1. What is the cost to perform a deep energy retrofit on exterior walls using an EIFS, and 

what is the relative cost effectiveness of various EIFS thicknesses in selected climate 

zones? 

2. What level of airtightness can be achieved with an exterior wall retrofit using an EIFS, 

recognizing that other components such as the ceiling, foundation, and windows will also 

contribute to air leakage?

3. Can prefabrication of EIFS wall panels reduce the cost and time for deep energy retrofits, 

and if so, by how much and under what circumstances? 

By answering these questions, this report attempts to bring attention to EIFSs’ potential 

application for residential deep energy retrofits, provide independent data on costs and potential 

performance targets, and provide guidance to practitioners. 

1.2 Relevance to Building America Goals

The overall goal of the U.S. Department of Energy’s Building America program is to “reduce 

home energy use by up to 50% (compared to 2009 energy codes for new homes and pre-retrofit 

energy use for existing homes)” (Building America Research for the American Home, 2013). As 

described above, increasing exterior wall insulation levels is critical to achieving deep energy 

reductions. Finding lower cost approaches for this will be important in gaining market 

penetration. 
3 

2 Background

EIFSs are common in commercial new construction and retrofits.1 Such products typically 

consist of five layers installed over the top of a weather resistive barrier: 

1. Adhesive 

2. Foam insulation

3. Reinforcing plaster or base coat

4. Reinforcing mesh embedded in the base coat

5. Top or finish coat. 

They can be applied to new or existing buildings that employ wood or masonry construction, and 

can utilize an insulation thickness of up to 16 in. However, such systems are rarely used in lowrise residential retrofits. Reasons for this might include a lack of demand for or knowledge of the 

systems in the residential retrofit industry, high cost, or lack of suitable distribution channels 

serving the residential market. Another barrier that may limit EIFS retrofits is the change in 

appearance that would result from converting a vinyl, clapboard or brick home to an EIFS home. 

The stucco appearance of EIFS is accepted in certain regions of the country such as the West and 

Deep South; however, in most colder regions, where energy retrofits can result in greater energy 

savings, EIFS is an uncommon look for homes. 

Off-site panelized EIFSs are further limited in present application, with no known examples of 

their use in low-rise residential retrofits. An example of an off-site panelized system is pictured 

in Figure 1. It includes rigid insulation with narrow metal channels embedded in the back for 

temporary fastening purposes, and a prefinished EIFS surface. Other materials required for this 

system include a water resistive barrier (either liquid applied or house wrap) over the building 

sheathing and sealant between panels. 

The insulation material most commonly used is EPS, which has a low cost per R-value compared

to other rigid board insulations. Unlike XPS, it contains little greenhouse gas agents (Wilson, 

June 2010); however, other compatible rigid board insulation materials could be used in place of 

EPS with little change to panel production or installation. 

 

1 For example, StoTherm Classic (http://www.sto.com/evo/web/sto/32331_EN-Products-Products_ystems.htm) has 

been used worldwide for 40 years. 
4 

Figure 1. Typical lightweight EIFS wall panel 

(courtesy of Sto Corporation) 

While the final appearance of an EIFS installation resembles stucco, it is a distinctly different 

system. Stucco is a generic cementitious-based material, whereas EIFSs are proprietary synthetic 

formulations distributed by manufacturers to a network of authorized applicators. An EIFS is 

composed of polymeric (organic) bonded aggregate and cement reinforced with a glass mesh. 

Stucco is made of inorganic cement, sand, and lime. 
5 

Figure 2. Field-applied EIFS showing yellow water resistive barrier, white EPS

insulation with yellow reinforcing mesh, and gray basecoat in foreground

In the western United States, stucco is the dominant residential exterior finish. The two most 

common stucco systems are the traditional three-coat system and the one-coat system. One-coat 

stucco is typically about a 1⁄2-in. thick base and finish layer and may be applied over a 1-in.-thick 

EPS insulation board. Three-coat stucco is typically 7⁄8-in. thick (Rapport, Davis, & Brozyna, 

2012), including scratch, base, and finish layers. EIFSs typically range in thickness from 1 in. to 

4 in., but can be as much as 16 in. thick. 

It merits noting that when EIFS became popular in the United States in the 1980s, there were a 

significant number of serious failures related to rain penetration. Early EIFSs used a face-sealed 

approach that required perfect installation and no deterioration and had no provision for 

drainage. This became a problem, especially because the system usually contained moisturesensitive materials such as gypsum board, oriented strand board, and other wood products. 

Drained EIFSs include a provision for drainage behind the foam insulation and can be 

successfully used as an exterior cladding system in most situations (Lstiburek, 2007). 
6 

3 Field Study

3.1 Approach 

One single-family detached home was retrofitted using a site-applied EIFS. Site-specific details 

were developed as required for the residential retrofit application. The EIFS thickness was 4 in. 

The 2-in. × 4-in. wall cavity was filled with blown-in cellulose as part of the overall retrofit 

project. Site work and costs of the EIFS were documented. Costs for a comparable off-site 

fabricated panel system were estimated with the assistance of panel fabricators. Envelope 

leakage was measured before and after EIFS application to assess the impact of the EIFS on 

infiltration.

3.2 Case Study Site

The case study site is a single-family detached frame home in Central Islip, New York. Basic 

characteristics of the home are provided in Table 1 and photographs of the pre-retrofit home are 

provided in Figure 3.

Table 1. Case Study Home Characteristics

Feature

Home Type Single-family detached

Conditioned Floor Area 2,200 ft2

Foundation Full unconditioned basement

Structure 2-in. × 4-in. wood frame

Exterior Vinyl siding—retrofit to 4-in. EIFS

Height Two stories above grade

Figure 3. Front and rear elevations of the pre-retrofit home

3.3 Exterior Insulation and Finish System Application

Off-site panelization and on-site fabrication were both considered for this project. On-site 

fabrication was chosen because the small scale of the project would have made setting up to 

produce panels cost prohibitive. The Appendix illustrates the major construction details used to 

apply the EIFS. 
7 

Figure 4 to Figure 12 illustrate the steps of the application process.

Figure 4. After scaffolding is set up a bottom track is attached to the base of the sheathing 

to accept the bottom of the EIFS. 

The bottom track serves to protect the edge of the EIFS and to assist in aligning the EPS panels 

during installation. It includes provisions for drainage. 

Figure 5. A liquid water resistive coating is brushed onto the sheathing; a layer of

reinforcing mesh is embedded into the coating at the sheathing joints. 

Overhangs at eaves were removed and added back on over rigid insulation to match the 4-in. 

EIFS thickness. At the gable ends, the roof deck was extended where necessary to match the 

4-in. EIFS depth. A metal drip edge was added to direct water away from the rake.
8 

Figure 6. After the coating is complete, more reinforcing mesh affixed 

around the newly installed windows; it will be used to wrap the edges of the insulation. 

The reinforcing mesh at the windows will be wrapped around the edges of the EPS panels, fully 

protecting them at all exposed surfaces. This obviates the need, in standard installations, for any 

additional window trim to be built out to the thickness of the added EIFS, thus eliminating a step 

required for other wall insulation retrofit techniques that use built-up insulation and siding.

Figure 7. Sections of EPS insulation, 4 in. thick and measuring 2 ft × 4 ft are 

adhered to the walls. Where necessary the backside of the panels are rasped to 

conform to irregularities in the substrate wall. The EPS joints are smoothed out. 

Smoothing the joints between EPS foam panels is essential to getting an even finish coat that 

avoids telegraphing joint lines. 
9 

Figure 8. EPS panels are placed around the new windows; an additional 1-in.

thick by 4-in. wide layer of EPS is used to form window trim. Other applied 

shapes can be used to create architectural forms as desired.

Figure 9. The gray basecoat is troweled on over an embedded layer of reinforcing mesh. 

The reinforcing mesh provides a durable surface. Additional layers of mesh can be added to 

increase impact resistance.

Figure 10. The basecoat is applied over the formed window trim and edges of the EPS panels, 

embedding the yellow mesh around windows and other penetrations. 
10 

Figure 11. The finish coat is mixed and applied with trowels. 

Figure 12. The finished system

Labor hours were logged for each major step in the process. Table 2 shows the labor breakdown. 
11 

Table 2. Labor Breakdown

*These steps require outdoor temperatures above 40°F for 24 hours after application and dry weather. 

Out of 19 nonholiday days during the EIFS application process from December 14, 2012 to 

January 10, 2013, 8 days were lost due to weather (either cold temperatures or rain). The total 

labor was 278 hours over 11 days. Gross wall area (including fenestration) was 2,122 ft2 and net 

wall area (not including fenestration) was 1,680 ft2

. Gross square feet per hour were 7.6 and net 

square feet per hour were 6. 

If this system were panelized off site, site labor would be reduced. The prep and water barrier 

labor would remain the same; however, the remaining tasks would be replaced by installation of 

the panels and the sealant joints. Total site labor for this home with off-site panelization might be

140–180 hours. 

Step Description Labor

Hours

Prep Work Set up two-story scaffold around entire house and install 

base track at bottom termination 28.0 

Water Barrier* Brush on liquid-applied coating with embedded mesh 

reinforcement at sheathing joints 40.0 

EPS Board Adhere 2-ft × 4-ft × 4-in. thick EPS boards and smooth 

joints; form window trim and cut drip edges 103.5 

Base Coat* Trowel on liquid-applied base coat with mesh reinforcement 53.0

Finish Coat* 

Trowel on 2-layer finish coat (single layer finish coats are 

also an option and would take approximately one half the 

time)

53.5 

Total 278.0
12 

4 Modeling

The case study home was modeled using version 2 of the National Renewable Energy 

Laboratory-developed Building Energy Optimization (BEoptTM) energy and cost analysis 

software. BEopt cases were run with EIFS thicknesses of 2 in., 4 in., and 6 in. plus a reference

case of vinyl siding. A post-retrofit enclosure air tightness of 2 ACH50 was used for the EIFS 

cases (case study house test result), compared to the 15 ACH50 pre-retrofit case. It was assumed 

that the vinyl siding was due for replacement (30 years old). The EIFS cases were compared to 

replacement with midrange vinyl siding at $4/ft2

 and to high-end vinyl siding at $7/ft2 (materials 

and labor). These vinyl siding costs were obtained from the contractor based on local costs. 

BEopt modeling looks at costs and energy consumption over a long-term project analysis period 

(30 years in this case). During that period other components of the home, particularly equipment, 

may be replaced when they reach their end of lifetime. BEopt incorporates the costs and benefits 

(in the form of improved efficiency of the new equipment) of these normal replacements into the 

long-term analysis. The annualized energy-related costs (as indicated in the tables below) of the 

retrofit are the initial retrofit costs, plus the future replacement costs, plus the costs of operation 

(energy) averaged over the analysis period. 

For the purposes of this modeling exercise the retrofit was assumed to include only the EIFS 

walls, ceiling insulation, and air sealing because these were the three items deemed “costeffective” in the BEopt analysis. Cost effectiveness of an energy efficiency measure is defined as 

having a lower annualized energy-related cost compared to not implementing the measure.

The major modeled characteristics of the house, including capital costs of the initial retrofit 

measures, are described in Table 3. Capital costs of items to be replaced in the future (at wear 

out) are not shown in the table because they would have to be incurred regardless of the initial 

retrofit.

Table 3. Modeled House Characteristics

Measure Pre-Retrofit Post-Retrofit Capital Cost at Time 

of EIFS Retrofit

Foundation Unconditioned 

basement No change

Floor R-19 fiberglass batts No change

Exterior Walls R-7 batt, grade III 

Add 4-in. EPS 

insulation as part of 

EIFS (R-16)

$32,719 (offsetting 

cost for new vinyl 

siding)

Windows Single pane clear, 

non-metal frame

Double pane clear 

vinyl at wear out

Ceiling R-19 fiberglass batts R-38 fiberglass batts $1,214

Infiltration 15 ACH50 2 ACH50 $6,152

Ventilation Exhaust No change

Heating Gas 72% AFUE 

furnace

78% AFUE furnace at 

wear out

Air Conditioning 10 SEER 13 SEER at wear out
13 

Measure Pre-Retrofit Post-Retrofit Capital Cost at Time 

of EIFS Retrofit

Ducts R-6 in attic and 

basement No change

Lighting Benchmark No change

Water Heating Gas standard No change

BEopt annual energy and utility bill savings are shown in Figure 13. Annualized utility bill 

savings are $1,028; source energy savings are 141.9 MMBtu/year. Carbon dioxide (CO2) 

emission reductions are 8.6 metric tons/year. 

Figure 13. BEopt modeled source energy savings and utility bill savings— 

Islip, New York; climate zone 4

BEopt optimization curves were generated for two scenarios considering EIFS retrofits with the 

other enclosure measures listed in Table 4. The optimization was run with two reference cases: 

midpriced vinyl siding (Figure 14) and high-end vinyl siding (Figure 15), both 30 years old (end 

of lifetime). BEopt runs multiple cases with various combinations of energy measures 

considered, over the 30-year analysis period. It then plots the annualized energy-related cost of 

each case against the percent source energy saved compared to the reference case (in these cases, 

replacing vinyl siding only). Each point on the plot represents one case. The curve developed 

along the bottom of the points is the lowest cost package of measures at a given percent savings. 

The optimal point (lowest overall annual energy related costs) is the bottom of the curve. The 

reference case is shown on the Y-axis at 0% energy savings. 

In the analysis with the midrange vinyl siding reference case (Figure 14), the bottom point of the 

optimization curve includes 4-in. EIFS, ceiling insulation, and air sealing. While this package is 

the optimal retrofit of the options analyzed in terms of annualized energy-related costs, it is 

higher in cost than replacing the siding with midrange vinyl alone (increase of $333). However, 

compared to high-end vinyl, the EIFS package has a lower annualized energy-related cost 

(decrease of $28) as shown in Figure 15. Other modeling assumptions are provided in Table 5. 

Vinyl siding costs are based on local prices obtained from the contractor. EIFS costs are based 

on actual project costs for 4-in. thickness and manufacturer estimates for other thicknesses.
14 

Table 4. Optimization Options

Figure 14. BEopt optimization curve with midrange vinyl siding reference (Islip, New York) 

Measure Considered Capital Cost Selected

Mid-Range Vinyl Siding $9,673 Reference A

High-End Vinyl Siding $16,928 Reference B

2-in. Thick EIFS $31,510 No

4-in. Thick EIFS $32,719 Yes

6-in. Thick EIFS $33,928 No

R-38 Fiberglass Batts Ceiling Insulation $1,214 Yes

Air Sealing to 2 ACH50 $6,152 Yes

R-5 Whole-Wall Basement Insulation $1,901 No

Double Pane Vinyl Windows $13,594 No
15 

Figure 15. BEopt optimization curve with high-end vinyl siding reference (Islip, New York) 

Table 5. Optimization Modeling Assumptions

Modeling was repeated for Boston, located in the U.S. Department of Energy climate zone 5. 

The reference home and costs were the same as those used for the Islip location. BEopt annual 

energy and utility bill savings are shown in Figure 16. Annualized utility bill savings are $1,265; 

source energy savings are 174.4 MMBtu/year. CO2 emissions reductions are 10.6 metric 

tons/year. 

Economic Variable BEopt Input

Project Analysis Period 30 years

Inflation Rate 3.0%

Discount Rate (Real) 3.0%

Loan Interest Rate 7.0%

Loan Period 5 years
16 

Figure 16. BEopt modeled source energy savings and utility bill savings (Boston) 

Figure 17 and Figure 18 show the optimization results for Boston. The same options were 

selected by BEopt (Table 4). Again, the 4-in. EIFS is the optimal retrofit of the options analyzed 

in terms of annualized energy-related costs. The optimal retrofit is $95 higher (annualized energy 

costs) than replacing the siding with midrange vinyl alone (Figure 17). Compared to replacement 

with high-end vinyl, the EIFS package has a $265 lower annualized energy cost (Figure 18). 

Figure 17. BEopt optimization curve with midrange vinyl siding reference (Boston)
17 

Figure 18. BEopt optimization curve with high-end vinyl siding reference (Boston)
18 

5 Discussion

Before proceeding with the proper installation of an EIFS, it is valuable to understand the cost 

and performance considerations. The following sections explore the risks, selection criteria, 

interactions with other building systems, cost, performance, and other aspects of using an EIFS 

in a deep energy retrofit.

5.1 Site and Safety Risks

EIFSs do not require special site safety precautions beyond general construction site precautions 

such as ladder safety, personal protection (goggles, hard hats, gloves) and other general 

Occupational Safety and Health Administration requirements. Some more specific cautions 

likely to apply to EIFS work include: 

• Use proper scaffolding assembly and adequate fall protection to avoid putting workers at 

risk.

• Utilize eye protection and respirators when sanding EPS insulation to avoid breathing in 

EPS dust. 

Unlike stucco, EIFS work does not involve handling dry stucco mix that can become airborne 

creating a risk of inhaling airborne silica. EIFS coatings arrive at the site premixed in pails and 

are water based.

5.2 Installation Risks 

Trapping moisture between two vapor/air barriers is a risk of all walls, including EIFS cladding 

applications if an interior vapor barrier exists and if there is not adequate ventilation through the 

drainage plane behind the insulation layer. To allow for drying of incidental moisture, EIFS

assemblies should not contain interior vapor barriers or impermeable interior finishes. “An 

important exception to this latter requirement is where the drainage plane is also a vapor 

impermeable air barrier membrane and the interior framing cavities are uninsulated” (Lstiburek, 

2007). Drying ability will be enhanced with adequate ventilation through the drainage plane. 

Note the drainage plane indicated in the details provided in the Appendix. 

In addition, as discussed above, bulk water must be managed; face-sealed approaches that rely on 

exposed sealants do not provide acceptable rain control or durability and are very risky.

5.3 Code and Regulatory Issues 

In most jurisdictions fire codes permit EIFSs for most building types and conditions. Generally, 

noncombustible details must be used at roof areas. This means that instead of plastic base track 

at roof setbacks and penthouses metal flashing must be used in conjunction with prebackwrapping (to 6 in.) of the EPS insulation with basecoat and mesh. 

Zoning ordinances may limit the extension of the building footprint beyond lot lines and past 

setback distances as caused by the addition to wall thickness. The additional footprint area may 

cause a building to exceed the maximum floor area limits, if such limits exist. Some jurisdictions 

are removing these barriers; for example, New York City recently revised laws to remove certain 

of these restrictions for energy retrofits (Urban Green Council, 2012).
19 

5.4 Trade Resources

Although EIFSs are not new, they may be new to the local residential construction industry and 

the local EIFS applicators may be unaccustomed to working on small-scale residential retrofits. 

There may be a learning curve as applicators figure out their cost structures for these new project 

types. Additionally, certain retrofit-specific details may need to be disseminated among 

applicators who are accustomed to new construction projects. 

Applicators familiar with prefabricated lightweight panel systems are even rarer. Because the 

market for this system is small, it may be difficult to get multiple bids and competitive pricing in 

many areas.

5.5 Maintenance

EIFSs require periodic (approximately every 5 years) inspections and possible maintenance to 

ensure sealant joints are intact. This is especially important for panelized systems that will 

typically have many more joints than field-applied projects. For large projects, factory-certified 

inspectors are available to do this work. On smaller low-rise buildings, an EIFS applicator can do 

the inspection. Cleaning also may be required (similar to other siding products) depending on the 

finish selected.

5.6 Durability and Reliability

The primary concern most homeowners will have when considering EIFS is the performance of 

the system in shedding water. Faulty system design and installation practices can cause problems 

with any cladding system; therefore, careful attention to waterproofing details is essential to long 

term durability. EIFSs with a moisture barrier and drainage plane behind the insulation can 

adequately protect the wall. The Appendix provides details showing one approach to achieving 

this design objective. The EIFS cladding is a durable exterior finish that will replace older 

cladding of unknown condition. Maintenance, as discussed above, is important to ensure 

durability. 

5.7 Occupant Comfort, Health, and Safety

The overall effect of adding exterior wall insulation is to improve comfort conditions for 

building occupants, versus a pre-retrofit wall assembly with high air leakage and little or no 

insulation. The added layer of continuous insulation provides a thermal break that reduces the 

heat flow rate through framing members and/or masonry and leads to more stable interior 

temperature conditions. 

The exterior insulation also should result in a quieter indoor environment. Furthermore, less 

outside air infiltration will result in less dirt and dust leaking into the home. However if the 

resulting home is too tight, mechanical ventilation may need to be added with a commensurate 

energy penalty.

5.8 System Interactions—Enclosure

Retrofitting an EIFS has implications for new or existing windows, doors, and other exterior wall 

penetrations. The overall wall thickness will increase by 2 in. or more. EIFSs can accommodate 

either an “innie” (window located at original wall surface as illustrated in the Appendix) or 

“outie” (window moved to the new outer wall surface). If windows or doors are being replaced at 

the time of the retrofit, then a choice can be made to leave them in the existing location at the 
20 

original wall surface (innies) or relocate them to the new outer wall surface (outies). For an outie 

configuration, new framing must be installed around the opening to support the window. Most 

masonry projects will retain an innie configuration because attaching framing to support the new 

window location is impractical.

An outie configuration is more costly to build (both for the exterior framing and wider interior 

trim) but allows for more robust waterproofing details. Aesthetics also play a role; innies will 

create recessed windows from the outside, outies will create deep window pockets on the 

interior.

Work also may be necessary to adjust roof overhangs to maintain an acceptable extension over 

the wall outer surface and to maintain clearance of soffit vents (Kosny, Fallahi, & Shukla, 2013).

5.9 System Interactions—Equipment

When adding a continuous layer of insulation to an exterior wall assembly, the overall R-value of 

the wall assembly will increase and will result in heating and cooling load reductions. This may 

result in the need for smaller capacity heating and cooling equipment, reduced ductwork, and 

potential redesign of the heating, ventilation and air-conditioning (HVAC) system. The overall 

effect is likely to reduce costs if equipment is being replaced. If equipment is not being replaced 

it may result in oversized equipment that could result in problems such as short-cycling or 

overheating if HVAC system controls are not altered to compensate. 

5.10 Application Alternatives

When considering an EIFS retrofit, a number of options are available related to waterproofing, 

finishes, thickness, and fabrication: 

5.10.1 Waterproofing

Building wrap or a liquid-applied water resistive barrier may be used as the waterproofing layer 

and drainage plane. Liquid-applied barriers are thought to perform better but often cost more on 

residential-scale projects. Also, the use of building wrap would render impossible the use of an 

adhesively bonded insulation layer and instead dictate mechanically fastened insulation. 

Mechanically fastened installation is quicker, especially in retrofits of older buildings where the 

sheathing may be out of plane, because the insulation does not have to be sanded on the backside 

to lie flat; rather, the fasteners pull it close to the sheathing. However, fasteners put many more 

holes in the water resistive barrier and also have been known to cause aesthetic problems. When 

the temperature difference between the interior and exterior of a house increases (during extreme 

cold or heat), the increased rate of heat loss or gain through the fasteners can become visible as 

condensation or frost that adheres to the exterior of the stucco where the fasteners are located. 

This is called ghosting. Over time, the parts that are damper tend to collect more dust from the 

air, and as a result, the ghosting becomes permanently etched in the wall surface. Eliminating 

this effect as well as improving the overall thermal performance of the wall system provides 

additional motivation to consider the adhesively applied system. 
21 

5.10.2 Finishes

Many finish colors and other options are available from EIFS suppliers. Most basic finishes are 

one coat. Upgrade finishes that are intended to resemble stone or brick are often two coats and 

may involve stenciled patterns.

5.10.3 Fabrication

EIFSs, while traditionally field applied, may also be fabricated off site into panels prior to 

installation on the building. Advantages of a panelized approach include: 

• Less dependence on warm, dry weather for construction. For example, about 40% of the 

EIFS application time for the case study project was lost due to weather-related work 

stoppage. 

• Less debris on site including packaging, pails of liquid materials, and most significantly 

EPS debris that results from rasping the backs of panels to fit on walls and at joints for 

site application.

• Reduced disturbance to building occupants during retrofits because of the shorter time on 

site. 

• Potentially lower cost for areas where site labor is expensive or working conditions are 

difficult.

Disadvantages of off-site fabricated panels include: 

• The additional sealant joints between panels may require another trade and additional 

periodic maintenance. Sealant joint inspection is recommended every 5 years. Inspection 

and maintenance of sealant joints may be difficult for taller buildings that require scaffold 

drops for access. 

• Smaller tolerance for site irregularities such as dimensional variation or out-of-plane 

walls that can be more easily accommodated with site fabrication.

• Higher costs for smaller projects where panels may require high degrees of 

customization. 

• Also, as discussed in Section 5.4, fabricators and applicators capable of delivering the 

panelized system may be hard to find. 

5.10.4 Thickness

EIFS thickness will be influenced by energy efficiency requirements and limited by practical 

issues such as detailing at openings, inside corners, and other locations. As little as 1 in. to as 

much as 16 in. is possible. 

5.11 Cost

One of the primary motivations of this project is to evaluate the cost effectiveness of the EIFS 

(both site and off-site fabricated) compared to the traditional approach of multiple layers of rigid 

board insulation, strapping and siding, and building out fenestration openings. 

Total material and labor costs for the case study site were tabulated and are shown in Table 6. 

This cost includes the water resistive barrier, 4-in. insulation, and base and finish coats. 
22 

Table 6. Case Study Site Costs

Increasing the thickness of the EIFS would add little to labor costs. Based solely on the added 

thickness of the EPS, the additional cost would be $0.20–$0.35/ft2 per additional inch of 

thickness.2

For off-site fabricated panels, a number of sources were contacted for estimates. The lowest costs 

for panel components was found to be $7–$8/ft2 for 2-in. thick panels with an additional 

$0.40/ft2 for each additional inch of thickness beyond 2 in. Adhesives and caulk are estimated at 

$0.50/ft2

. Site labor is highly variable depending on the building configuration and experience of 

the contractor.

5.12 Energy Efficiency

The continuous layer of EPS insulation that is part of the EIFS enhances the thermal 

performance of the wall in every climate zone. When installed against a frame wall system, the 

continuous exterior insulation reduces the effects of thermal bridging. As a result, building

owners will have lower heating and cooling costs. Energy savings as projected by the modeling 

described above indicates that under certain conditions an EIFS retrofit can be cost effective (i.e., 

lower annualized energy related cost) if exterior cladding is in need of replacement. The specific 

return on investment will depend on the existing building condition, energy prices, equipment 

efficiency, retrofit characteristics, and the cost of the alternative cladding system. High fuel prices 

(e.g., oil heat rather than gas), a cold climate, poorly insulated existing walls, leaky existing walls, 

and low retrofit costs (relatively simple geometry) will improve the cost effectiveness of an EIFS 

retrofit. 

 

2 Cost extrapolation based on input from Sto Corp. and http://www.ecoevaluator.com/building/energyefficiency/insulation-application-and-cost.html.

Based on Gross 

Wall Area

Based on Net Wall Area 

(Deducting Fenestration)

EIFS Cost $32,000 $32,000

Wall Area 2,374 ft2 2,075 ft2

Cost per Square Foot $13.47 $15.42
23 

6 Conclusions 

This research addressed three primary research questions, each of which is repeated below along 

with the respective results.

1. What is the cost of a deep energy exterior wall retrofit using an EIFS, and what is the 

relative cost effectiveness of various EIFS thicknesses in selected climate zones? 

The costs for the case study project were about $15.50/ft2 of net wall area for a 4-in.-thick EIFS, 

including the water resistive barrier and a standard finish coat. Costs for other insulation 

thicknesses mainly vary with material costs, because the labor does not change significantly. 

Extrapolated costs for 2-in. and 6-in. thicknesses are $15 and $16, respectively. BEopt modeling 

indicates that 4-in. thickness results in lower annualized energy-related costs compared to 2-in. 

and 6-in. thicknesses for a sample retrofit in climate zones 4 and 5. The 4-in. system can be cost 

effective (i.e., have a lower annualized energy cost compared to no retrofit) when the existing 

siding is at the end of its lifetime and the alternative is a high-end vinyl siding or similar cost 

replacement.

2. What level of airtightness can be achieved with an exterior wall retrofit using an EIFS, 

recognizing that other components such as the ceiling, foundation, and windows will also 

contribute to air leakage?

The Gibbs Road case study project achieved a blower door test result of 2 ACH50. No in-process 

diagnostic blower door tests were conducted and no remedial air sealing was needed to obtain 

this result. While this is an indication of how tight an EIFS home can be, superior construction of 

the other components, such as the foundation, ceiling, and windows, contributed to the low air 

leakage test result compared to pre-retrofit rate of 15 ACH50).

3. Can prefabrication of EIFS wall panels reduce the cost and time for deep energy retrofits, 

and if so, by how much and under what circumstances? 

Benefits of panelization include greater speed and schedule reliability that can potentially 

convert to cost savings, less dust and dirt on site that are a result of rasping backs of panels to fit 

on walls for a site-fabricated system, and greater safety because of less time on scaffolds and 

fewer trips around the building. Prefabricated panels may be less costly for certain projects under 

certain conditions such as in poor weather and/or where site labor costs are high or working 

conditions difficult. Prefabricated panels can be delivered to the site for approximately $7–$9/ft2

(net panel area). If proficient applicators can install the water resistive barrier and panels for 

under $6/ft2

 then off-site panelization becomes a viable alternative to site-applied systems. 

Another case study using an off-site panelized EIFS is in progress.
24 

References

Aldrich, R. A., Arena, L., & Zoller, W. (2010). Practical Residential Wall Systems: R-30 and 

Beyond. Norwalk, CT: Steven Winter Associates, Inc.

Bailey, C. (2012, June 26). Green Architect's Lounge. Retrieved March 9, 2012, from Green 

Building Advosor: http://www.greenbuildingadvisor.com/blogs/dept/green-architectslounge/what-deep-energy-retrofit

Building Science Corporation. (2010). Bedford Farmhouse High Performance Retrofit Prototype. 

Sommerville, MA: Building Science Corporation. 

Canova, D. (2013, April 8). Costs of EIFS systems. (J. Dentz, Interviewer) 

Holladay. (2012, March 2). Musings of an Energy Nerd. Retrieved March 9, 2012, from Green 

Building Advisor: http://www.greenbuildingadvisor.com/blogs/dept/musings/high-cost-deepenergy-retrofits?utm_source=email&utm_medium=eletter&utm_term=deep-energyretrofit&utm_content=20120307-deep-energy-retrofits&utm_campaign=green-building-advisoreletter

Jan Kosny, A. F. (2013). Cold Climate Building Enclosure Solutions. Cambridge: Fraunhofer 

CSE.

Kosny, J., Fallahi, A., & Shukla, N. (2013). Cold Climate Building Enclosure Solutions. 

Cambridge, MA: Fraunhofer CSE. 

Lstiburek, J. (2007). Building Science Digest 146: EIFS - Problems and Solutions. Sommerville, 

MA: Building Science Press.

National Renewable Energy Laboratory. (n.d.). National Residential Energy Efficiency Measures 

Database. Retrieved May 13, 2013, from National Renewable Energy Laboratory: 

http://www.nrel.gov/ap/retrofits/measures.cfm?gId=12&ctId=410&scId=6547 

Neuhauser, K. (2013, April 29). How Do We Retrofit the Tough Buildings? Cape Cod Style and 

Masonry. Denver. 

Pedrick, G. (2011, June 8). (J. Dentz, Interviewer) 

Peter Baker, P. (2012). TO2 7.2.3 External Insulation of Masonry Walls & Wood Framed Walls: 

Final Report. Sommerville: Building Science Corporation.

Rapport, A., Davis, G., & Brozyna, K. (2012). Measure Guideline: Transitioning From ThreeCoat Stucco to One-Coat Stucco With EPS. Pittsburgh, PA. 

Straube, J., & Smegal, J. (2009). Building America Special Research Project: High-R Walls Case 

Study Analysis. Sommerville, MA: Building Science Corporation. 
25 

Urban Green Council. (2010). NYC Green Codes Task Force: Full Proposals EO6. Retrieved 2 

22, 2012, from New York Chapter of the U.S. Green Building Council : 

http://www.urbangreencouncil.org/FullProposal 

Urban Green Council. (2012, August 8). NYC GREEN CODES LEGISLATIVE TRACKER. 

Retrieved April 25, 2013, from Urban Green Council: 

http://www.urbangreencouncil.org/ProposalStatus 

Wilson, A. (2009, July 15). How Much Insulation is Needed? Retrieved April 2, 2013, from 

Green Building Advisor: http://www.greenbuildingadvisor.com/blogs/dept/energysolutions/how-much-insulation-needed

Wilson, A. (June 2010). Avoiding the Global Warming Impact of Insulation. Environmental 

Building News. 
26 

Appendix: Construction Details

Figure 19. Eave detail. The existing eave was removed. 

(adapted from Fusion Architects)

To construct this eave detail, the existing eave overhang was removed by cutting off the rafter 

tails (often referred to as a chainsaw retrofit). Rigid foam insulation was added to the roof along 

with new roof sheathing and shingles that extend beyond to join with a new bolted-on eave 

assembly. The new eave assembly may be added after the EIFS is installed, or if (as is likely) the 

roof is installed first, then rigid insulation that matches the EIFS thickness can be installed 

behind the eave and the EIFS subsequently mated to it. The result is a continuous blanket of 4 in. 

(in this case) rigid insulation over the walls and roof, virtually eliminating thermal bridges.
27 

Figure 20. Detail at porch roof. A 2-in. gap is left between at the bottom of the upper wall EIFS. 

(adapted from Fusion Architects)

The wall at a roof-wall intersection is treated similar to at the foundation with a starter track and 

gap (minimum 2 in.) to provide drainage and facilitate future roof replacement without damaging 

the EIFS.
28 

Figure 21. Detail at foundation 

(adapted from Fusion Architects)

The EIFS should be kept at least 8 in. above grade to prevent dirt from clogging the bottom track 

weep holes. This detail includes interior rigid foam basement wall insulation and closed cell 

spray foam at the rim joist for a continuous thermal enclosure. 
29 

Figure 22. Detail at window head. The water resistive barrier ties into the window flashing. 

(figure adapted from Fusion Architects) 
30 

The window head detail includes a 1-in. × 4-in. casing detail built into the EIFS for architectural 

detail. It includes a kerf cut so water drips off the EIFS rather than running under the head 

towards the window. In this case study the windows were replaced in their original location at 

the sheathing surface of the existing wall. Window flashing was tied into the EIFS water resistive 

barrier. In an EIFS retrofit where windows are not replaced, care would need to be taken to 

ensure that window openings were adequately flashed and tied into the new water barrier. 

Figure 23. Detail at window sill 

(adapted from Fusion Architects)

Window sill flashing must tie into the new EIFS water resistive barrier, making sure that the 

drainage gap remains open from the window down to the bottom of the wall. The EIFS foam was 

built out to form a trim detail along the bottom of the window. The sill is sloped so water, 

including water that drips down from the kerf cut at the window head, flows to the outside. 
31 

Figure 24. Detail at rake

The new roof sheathing extends out beyond the existing wall to overhang the new EIFS. A metal 

drip edge protects the top of the EIFS from water intrusion. 
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