Short-Term Monitoring 

Results for Advanced New 

Construction Test House—

Roseville, California

D. Stecher, K. Brozyna, and C. Imm

IBACOS, Inc.

September 2013
NOTICE

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iii

Short-Term Monitoring Results for Advanced 

New Construction Test House—Roseville, California

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: 

D. Stecher, K. Brozyna, and C. Imm

IBACOS, Inc.

2214 Liberty Avenue

Pittsburgh, PA 15222

NREL Technical Monitor: Michael Gestwick

Prepared under Subcontract No. KNDJ-0-40341-02

September 2013
iv

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v

Table of Contents

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

List of Tables ............................................................................................................................................. vii

Definitions................................................................................................................................................. viii

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

Acknowledgments ...................................................................................................................................... x

1 Introduction and Background ............................................................................................................. 1

1.1 Overview of the Builder.......................................................................................................1

1.2 Prototype House...................................................................................................................1

2 Design Development and Energy Modeling ...................................................................................... 3

2.1 Systems Integrated Measures Package Development..........................................................3

2.1.1 Slab Edge Insulation ................................................................................................3

2.1.2 Walls........................................................................................................................5

2.1.3 Systems Integrated Measures Package Comparison................................................6

2.1.4 Strategy for Locating Ductwork in Conditioned Space...........................................9

2.2 Whole-House Energy Modeling ........................................................................................14

2.3 Test Plan Development......................................................................................................16

2.3.1 Research Questions................................................................................................16

3 Short-Term Tests................................................................................................................................ 19

3.1 Room-by-Room Supply Register Airflow.........................................................................19

3.1.1 Methods..................................................................................................................19

3.1.2 Results....................................................................................................................19

3.1.3 Discussion..............................................................................................................20

3.2 Duct Air Leakage...............................................................................................................20

3.2.1 Methods..................................................................................................................20

3.2.2 Results....................................................................................................................20

3.2.3 Discussion..............................................................................................................21

3.3 Whole-Building Air Leakage.............................................................................................21

3.3.1 Methods..................................................................................................................21

3.3.2 Results....................................................................................................................21

3.3.3 Discussion..............................................................................................................22

3.4 Recessed Light Fixture and Wall Penetration Air Leakage...............................................22

3.4.1 Methods..................................................................................................................22

3.4.2 Results....................................................................................................................22

3.4.3 Discussion..............................................................................................................22

3.5 Room-to-Room Pressure Balancing ..................................................................................23

3.5.1 Methods..................................................................................................................23

3.5.2 Results....................................................................................................................23

3.5.3 Discussion..............................................................................................................23
vi

3.6 Infrared Flow Visualization ...............................................................................................23

3.6.1 Methods..................................................................................................................23

3.6.2 Results....................................................................................................................24

3.6.3 Discussion..............................................................................................................28

3.7 In-Room Temperature Uniformity Measurements ............................................................28

3.7.1 Methods..................................................................................................................28

3.7.2 Results....................................................................................................................30

3.7.3 Discussion..............................................................................................................32

4 Conclusions ........................................................................................................................................ 33

5 References .......................................................................................................................................... 34
vii

List of Figures

Figure 1. Front elevation of the test house .............................................................................................. 2

Figure 2. Slab edge insulation detail......................................................................................................... 4

Figure 3. Mechanical equipment and ductwork within unconditioned space of the vented attic .... 10

Figure 4. Mechanical equipment and ductwork within the semiconditioned bulkhead space 

at the floor of the vented attic ........................................................................................................... 10

Figure 5. Standard roof truss for the builder’s Plan 4 houses............................................................. 11

Figure 6. Modified roof truss for the Plan 4 test house, which provides a chase for ductwork 

at the ceiling plane and has 16-in. raised heels along the perimeter............................................ 12

Figure 7. Final layout of the centrally located bulkhead and mechanical equipment inside 

a closet ................................................................................................................................................ 13

Figure 8. Ductwork centrally distributed within the conditioned space of the bulkhead at the 

attic floor ............................................................................................................................................. 14

Figure 9. Output from BEopt source energy modeling by subcategory ............................................. 16

Figure 10. Low-flow balometer testing ................................................................................................... 19

Figure 11. Blower door testing ................................................................................................................ 21

Figure 12. Black felt IR viewing screen positioned adjacent to an exterior wall and parallel to 

the primary register airflow path....................................................................................................... 24

Figure 13. IR photo of black felt screen during cooling system operation (temperature scale 

in °F)..................................................................................................................................................... 25

Figure 14. IR photo of black felt screen during heating system operation (temperature scale 

in °F)..................................................................................................................................................... 26

Figure 15. IR photo of black felt screen shortly after system turnoff, clearly showing 

stratification (temperature scale in °F)............................................................................................. 26

Figure 16. IR photo showing vertical stratification (temperature scale in °F) .................................... 27

Figure 17. IR photo showing uniform horizontal distribution of heated air (temperature scale 

in °F)..................................................................................................................................................... 27

Figure 18. Layout of temperature measurements ................................................................................. 29

Figure 19. Sensor stands and a supply register in the kitchen/family room area.............................. 30

Figure 20. Temperatures (°C) at various sensor locations in the kitchen/family room area 

during 1 h ............................................................................................................................................ 31

Figure 21. Temperatures (°C) at various sensor locations in the master bedroom during 1 h ........ 32

Unless otherwise noted, all figures and photos were created by IBACOS.

List of Tables

Table 1. SIMPs for K. Hovnanian Homes.................................................................................................. 7

Table 2. Sample of Modeling Results from Mechanical Equipment and Ductwork Location 

Evaluation.............................................................................................................................................. 9

Table 3. Comparison of Standard Versus Prototype House Specifications....................................... 15

Table 4. Research Measurements and Equipment for Short-Term Characterization Tests.............. 18

Table 5. Pressure Balancing Results for Each Room. .......................................................................... 20

Table 6. Duct Air Leakage Test Results.................................................................................................. 20

Table 7. Characterization Testing: House Leakage............................................................................... 22

Unless otherwise noted, all tables were created by IBACOS.
viii

Definitions

ACCA Air Conditioning Contractors of America

ACH Air changes per hour

AFUE Annual fuel utilization efficiency

AHU Air-handling unit

BA Building America

BEopt Building Energy Optimization 

CEC California Energy Commission

cfm Cubic foot per minute

EF Energy factor

FF Finished floor

HERS Home Energy Rating System

HVAC Heating, ventilation, and air conditioning

ICC International Code Council

IR Infrared

kW Kilowatt

kWh Kilowatt-hour

Pa Pascal

PV Photovoltaic

SEER Seasonal energy efficiency ratio

SHGC Solar heat gain coefficient

SIMP Systems integrated measures package

XPS Extruded polystyrene
ix

Executive Summary

A test house constructed in Roseville, California, has a modeled energy savings of 60% with 

respect to the Building America House Simulation Protocols (Hendron and Engebrecht 2010). 

This prototype is a 2,253-ft2 single-story slab-on-grade ranch house with three bedrooms and two 

full bathrooms. 

To accomplish this increase in energy efficiency while minimizing construction costs, the builder 

(K. Hovnanian Homes), design consultant, and trades collaborated to identify a systems 

integrated measures package. This design development process for the test house lasted from late 

November 2010 through early July 2011. 

One of the key building improvements that the team chose to incorporate was applying R-10 

insulation to the slab edge. This strategy consisted of insulating the slab edge on the exterior 

from 1 in. below the finished floor to a depth of 15 in. below the finished floor with 2-in.-thick 

extruded polystyrene (R-10 total). 

Several alternatives were considered to improve the thermal performance of the walls, but the 

decision was made to increase the standard-density R-13 fiberglass batt in the wall cavity with a 

higher density R-15 fiberglass batt. The attic insulation also was increased from R-30 to R-38. 

Regarding placement of the mechanical heating, ventilation, and air-conditioning equipment, the 

air-handling unit was relocated from the unconditioned attic to a central location inside the 

conditioned space of the house. Likewise, the ductwork was relocated within the thermal 

enclosure along the attic floor by building an insulated bulkhead above it. All energy 

improvements were implemented without requiring changes to the drawings that would impact 

local code or zoning approval. 

IBACOS used a combination of REM/RateTM and EnergyGauge USA modeling to evaluate the 

whole-house energy consumption of the prototype. Energy modeling using Building Energy 

Optimization Version 1.3 was also performed. Although models predicted that the builder’s 

standard inputs would provide a savings of 11.8% relative the Building America House 

Simulation Protocols (Hendron and Engebrecht 2010), the prototype house specifications 

provided savings of 35% without photovoltaics and 60% with photovoltaics (both relative to the 

Building America House Simulation Protocols; see Hendron and Engebrecht 2010).

Research questions focused on measuring the performance of the proposed space conditioning 

system and the capacity of the system to maintain acceptable levels of indoor temperature and 

relative humidity. Short-term testing and commissioning of long-term monitoring equipment 

were performed. 

The airflow from each supply register in each room was measured using a calibrated low-flow 

balometer, and the tightness of the air distribution system was tested with a duct blaster to 

determine the total air leakage in the system and, in conjunction with the blower door test, to 

determine air leakage to the outdoors. During the blower door test, further testing was conducted 

to measure air leakage around recessed light fixtures and wall penetration air leakage. 
x

A digital manometer was also used to measure the pressure difference between rooms with the 

doors closed to the central space while the mechanical system was operating to ensure the 

installed over-the-door transfer grilles operated as an adequate passive return pathway. 

Flow visualization testing using an infrared thermal imaging camera was conducted in the master 

bedroom to determine the temperature uniformity of those spaces provided by the compact duct 

system layout and the use of ceiling-mounted supply distribution. Further in-room temperature 

uniformity measurements were also conducted at five critical locations throughout the master 

bedroom and six locations throughout the kitchen/family room area.

The results of the short-term testing showed that duct air leakage was low, as anticipated, due to 

the short duct runs and the placement of the ductwork in conditioned space. Whole-building air 

leakage improved considerably after air sealing all penetrations through the drywall. However, 

recessed light fixture and wall penetration leakage showed significant air leakage levels, and 

exhaust fans represented another source of air leakage.

One problem foreseen during planning was realized during commissioning, where the lack of 

access for servicing the ductwork and dampers in the bulkhead area prevented retroactive 

balancing of individual branches, resulting in significant differences between specified and 

measured airflow values for some duct runs. The results of thermal imaging performed for the 

house when operating in both the heating mode and the cooling mode showed that the alternative 

register placement in the test house provided equivalent horizontal distribution to the builder’s 

standard house. The tests validated historical stratification issues of ceiling supply registers with 

high supply air temperatures.

Long-term monitoring results for this test house will be detailed in a future report after at least

1 year of monitored data has been collected.

Acknowledgments

This report was prepared for the U.S. Department of Energy Building America program. Funding 

for this work was provided by the National Renewable Energy Laboratory under Subcontract 

No. KNDJ-0-40341-02.

The authors wish to thank Ed Hancock and Lieko Earle for their assistance in short-term testing 

and monitoring equipment commissioning.
1

1 Introduction and Background

1.1 Overview of the Builder

K. Hovnanian Homes is headquartered in Red Bank, New Jersey. Founded more than 50 years 

ago, K. Hovnanian Homes has grown into a company with divisions building homes in 199 

communities across 16 states. In 2011, the company had 4,316 closings and was ranked the 

nation’s seventh largest builder of new homes in the United States by Professional Builder

magazine. 

1.2 Prototype House

The prototype house is located in the Stone Mill community of the Fiddyment Farm master plan 

in the northwest portion of the City of Roseville, within Placer County, California. The 

development of this community is considered part of K. Hovnanian Homes’ Sacramento region, 

which is overseen by its Northern California group. The community is composed of 135 home 

sites and offers several one- and two-story slab-on-grade plan types ranging in size from 

approximately 2,500 to 3,750 ft2. With prices starting in the mid- to upper $300,000 range, these 

homes are priced closer to the upper end of the market and are targeting second-time and moveup home buyers. 

The Northern California group of K. Hovnanian Homes decided to participate in the Building 

America (BA) program with IBACOS to design and construct a test house with several goals in 

mind:

• Evaluate the benefits, costs, and challenges of the technologies and building practices that 

are available on the market and that can be readily incorporated into current production.

• Experiment with those technologies that will enable compliance with upcoming building 

code cycles in order to be prepared when higher performing codes are required in the 

future.

• Provide the builder’s trade contractors the opportunity to recommend and construct 

alternative practices for bringing mechanical equipment and ductwork inside the 

conditioned space and improving the overall thermal performance and airtightness of the 

building enclosure.

• Demonstrate to the regional team and trade contractors the benefits of using a wholehouse systems integrated approach to designing and constructing a home.

The builder elected to construct a ranch-style house in Roseville, California, that would achieve 

the 60% level of source energy savings in relation to the BA House Simulation Protocols

(Hendron and Engebrecht 2010). A popular house type that K. Hovnanian Homes develops in the 

region, Plan 4 is a 2,253-ft2 single-story slab-on-grade home that has three bedrooms and two 

full bathrooms. Figure 1 shows the front elevation of the test house. 
2 

Figure 1. Front elevation of the test house

The current standards for the builder’s Northern California group are is ENERGY STAR® 2.0 

and Title 24 of the California Building Code (California Building Standards Commission 2007). 

Selection of the systems integrated measures package (SIMP) for the test house to achieve the 

60% level of energy savings required several months of iterative design and costing analysis in 

early 2011. During this process, modeling was performed using a combination of Building 

Energy Optimization (BEopt) Version 1.3, EnergyGauge USA Version 2.8.03, and REM/Rate 

Version 12.96 to demonstrate the impact on whole-house energy use among various building 

SIMPs while using the California Energy Commission (CEC) 2008 Building Energy Efficiency 

Standards requirements as a baseline for comparing the various packages (CEC 2010). 

BEopt Version 1.3 was used to evaluate the current level of building performance of the entire 

division, with the builder’s standard specification package achieving an 11.8% level of source 

energy savings with respect to the BA House Simulation Protocols (Hendron and Engebrecht 

2010) using a combination of REM/Rate Version 12.96, EnergyGauge USA Version 2.8.03, and 

BEopt Version 1.3 modeling tools. 
3

2 Design Development and Energy Modeling

2.1 Systems Integrated Measures Package Development

The design development process for the test house began in late November 2010 and ended in 

early July 2011. During this time, IBACOS worked with the builder to perform several rounds of 

modeling to evaluate the impact on whole-house energy performance and cost for various 

building enclosure components that included exterior walls, insulated ceiling assembly, slab edge 

insulation, windows, and building envelope airtightness. Ultimately, the goal of the enclosure 

evaluation was to identify a cost-effective insulation strategy for the building envelope that 

would help reduce the heating and cooling load requirements of the home and would allow for 

the mechanical equipment and ductwork to be centrally located within conditioned space. 

Locating the mechanical equipment and ductwork inside conditioned space was a key feature in 

the design of the home because the builder recognized that regional building codes are moving 

toward making this building practice mandatory. 

The builder’s team is very conscious of the impact that building systems improvements may 

have on the construction cost of its homes if trade-offs are not evaluated as part of a whole-house 

systems approach to design. Consideration of existing, as well as upcoming, code requirements 

was a critical part of the evaluation process for the builder. Identifying the building practices that 

would allow the builder to satisfy the requirements of the 2008 Building Energy Efficiency 

Standards (CEC 2010) and prepare for the proposed 2013 code and ENERGY STAR Version 3.0 

requirements were the basic guidelines for the packages of measures outlined. The key building 

improvements that the builder wanted to incorporate were changes to the slab edge, exterior 

walls, and attic insulation. These improvements would allow the company to reduce the size of 

the mechanical equipment and consider bringing it inside the conditioned space at a central 

location in the house.

2.1.1 Slab Edge Insulation

As a result of the increased focus of upcoming codes on reducing energy loss through the floor 

slab (International Energy Conservation Code 2009; 2012), IBACOS worked with the builder to 

evaluate the impact and benefit of introducing insulation at the foundation level. Several 

approaches were analyzed, including horizontal insulation under the entire slab, horizontal 

insulation around the inside perimeter of the slab, and vertical insulations along the interior and 

exterior portions of the footings.

After discussions with the builder, it was determined that the strategy with the best energy 

performance—insulating the slab edge and underside of the footing—would not be practical to 

construct in a reasonable time frame due to perceived difficulties in receiving approval from 

local code officials for the use of foam under a load-bearing portion of the foundation. The 

builder’s team agreed to the slab edge insulation strategy shown in Figure 2.

1 The strategy 

consists of insulating the slab edge on the exterior from 1 in. below the finished floor (FF) to a 

depth of 15 in. below the FF with 2-in.-thick extruded polystyrene (XPS; R-10 total). Although 

 1 The open stud framing method shown in Figure 2 is prevalent in the southwestern United States (e.g., Southern 

California, Nevada, Arizona, and New Mexico). For the most part, the building paper is unsupported (i.e., there is 

“let-in” bracing and/or shear panels but no wood sheathing over most of the wall plane).
4

the XPS does not cover the entire height of the slab edge, it is the solution that provided the best 

insulation for its installation efforts. 

Figure 2. Slab edge insulation detail

To implement this strategy, the foundation contractor was asked to install an additional 8-in.-

high form board to the bottom of the existing one to ensure that there was a minimum of 18 in. of 

smooth slab edge down from the FF. After the form work was removed, the foundation 

contractor applied the foam to the edge of the slab. To allow for the detailing of the termite break 
5

and flashing details, the top of the foam was located 1 in. below the FF height. It extended to 

15 in. below the FF height for a total of 14 in. of foam board. The foam was held in place by 

construction adhesive and backfill at the slab edge.

Several finishes for the foam were evaluated, including painted galvanized sheet metal, selfadhering flexible polyvinyl chloride sheet material, and troweled-on stucco. Concerns with longterm maintenance and ease of repair led the team to select troweled-on stucco as the finish. This 

also allowed for the best color and finish match between the slab edge and the above-grade wall. 

2.1.2 Walls

For the exterior walls, IBACOS and the builder discussed several opportunities to increase the 

thermal performance of the walls. The builder’s standard wall assembly consisted of 2 × 4 wood 

framing, with R-13 batts in the cavity and a one-coat stucco system (including R-3 expanded 

polystyrene insulating sheathing) on the exterior. The following possible improvements were 

discussed with the builder and its trade contractors:

• Changing the framing from 16-in. on-center (o.c.) 2 × 4 boards to 24-in. o.c. 2 × 6 boards

• Using a higher R-value/inch rigid insulation board on the exterior in conjunction with the 

one-coat stucco system

• Using higher R-value/inch cavity fill insulation.

It was determined that making the shift to a 2 × 6 advanced framed wall required unacceptable 

changes, including reducing the interior square footage of the home (which would require the 

plan set to be redrawn and reapproved by the township) and changing the window and door 

frame details. 

Discussed next were the options of changing the R-3/inch expanded polystyrene board used with 

the one-coat stucco system to either R-5/in. XPS board or R-6.5/in. polyisocyanurate board. 

When reviewed with the stucco contractor, it was determined that neither of these alternative 

boards had been approved for use with the stucco system, which was a fire-rated assembly. 

Therefore, without additional testing and certifications being pursued, neither of these options 

could be used. 

The remaining improvement considered was swapping the standard-density R-13 fiberglass batt 

in the wall cavity with a higher-density R-15 fiberglass batt. The builder realized that the impact 

on the design and installation process of the cavity insulation would be negligible and agreed to 

incorporate this change. 

Because the monolithic stucco finish contributed to exterior walls that were inherently airtight, 

attention turned to air sealing the attic. This was accomplished by applying spray foam insulation 

to the penetrations into the attic and at junctions between the top plates of interior partition walls 

and ceiling drywall. In addition to these improved enclosure measures, which led to reduced air 

infiltration through the building envelope, IBACOS recommended that the builder should 

consider ventilation strategies to ensure that outside makeup air would be introduced into its 

homes as well. 
6 

2.1.3 Systems Integrated Measures Package Comparison

As a result of these discussions, IBACOS developed the packages of measures listed in Table 1 

to fulfill the requirements outlined by the builder. The table shows the system improvements 

made among the various packages, as well as the estimated source energy use and Home Energy 

Rating System (HERS) Index for each package of measures.

During the SIMP evaluation process, the builder’s marketing team requested that IBACOS 

develop a comprehensive analysis of how houses available in the region compare to the builder’s

standard product, as well as the high performance packages that were being considered for the 

test house. Incorporating this added level of evaluation into the analysis would enable the 

builder’s sales team to demonstrate to potential customers the anticipated savings they could 

experience when purchasing a new home from the builder versus an older home on the market. 

Therefore, based on input from the builder about the typical age of homes available on the 

market, IBACOS developed two SIMPs that represented homes constructed to the 1990s and 

early 2000s code levels of performance. Table 1 includes both SIMPs. 

A note about modeling should be added here. Initially, IBACOS utilized BEopt and 

EnergyGauge USA to conduct the whole-house energy modeling. Feedback from the builder was 

that the modeling results were not useful for its evaluation because those modeling results did 

not relate to a performance metric with which the builder or its building raters were familiar. 

Therefore, IBACOS chose to use REM/Rate software because the builder’s energy rating 

consultants use it and because the output from that program would provide a HERS Index, a 

widely accepted industry metric with which the consultants would be familiar. 
7

Table 1. SIMPs for K. Hovnanian Homes

SIMPs

Building 

System

1990s 

House

2000s 

House

Standard 

House

Standard 

House with 

Slab Edge 

Insulation

Option 1

Option 1 

with 

Slab Edge 

Insulation

Option 2

Option 2 

with 

Solar 

PV

Enclosure

2 × 4 wood 

framed, R-11 

batt cavity 

insulation, 

R-30 blown 

insulation at 

attic floor, 

windows 

U = 0.65 and 

SHGC = 0.70, 

ACH50 = 8

2 × 4 wood 

framed, R-13 

batt cavity 

insulation, 

R-30 blown 

insulation at 

attic floor, 

windows 

U = 0.60 and 

SHGC = 0.40, 

ACH50 = 6

2 × 4 wood 

framed, R-3 

one-coat stucco, 

R-13 batt cavity 

insulation, R-30 

blown insulation 

at attic floor, 

windows 

U = 0.35 and 

SHGC = 0.30, 

ACH50 = 3

2 × 4 wood 

framed, R-3 

one-coat stucco, 

R-13 batt cavity 

insulation, R-30 

blown insulation 

at attic floor, 

windows 

U = 0.35 and 

SHGC = 0.30, 

ACH50 = 3, 

R-10 slab edge 

insulation 

vertical around 

the exterior 

perimeter

2 × 4 wood 

framed, R-3 

one-coat stucco, 

R-13 batt cavity 

insulation, R-38 

blown insulation 

at attic floor, 

windows 

U = 0.35 and 

SHGC = 0.30, 

ACH50 = 3

2 × 4 wood 

framed, R-3 

one-coat stucco, 

R-13 batt cavity 

insulation, R-38 

blown insulation 

at attic floor, 

windows 

U = 0.35 and 

SHGC = 0.30, 

ACH50 = 3, 

R-10 slab 

insulation 

vertical around 

the exterior 

perimeter

2 × 4 wood 

framed, R-3 onecoat stucco, R-15 

batt cavity 

insulation, R-38 

blown insulation 

at attic floor, 

radiant barrier at 

roof deck,

windows 

U = 0.28 and 

SHGC = 0.26, 

ACH50 = 1.7, 

R-10 slab 

insulation vertical 

around the 

exterior perimeter

2 × 4 wood 

framed, R-3 onecoat stucco, R-15 

batt cavity 

insulation, R-38 

blown insulation 

at attic floor, 

radiant barrier at 

roof deck, 

windows 

U = 0.28 and 

SHGC = 0.26, 

ACH50 = 1.7, 

R-10 slab 

insulation vertical 

around the 

exterior perimeter

Heating

78% AFUE gas 

furnace, no 

ventilation

80% AFUE gas 

furnace, no 

ventilation

80% AFUE gas 

furnace, exhaust 

only ventilation

80% AFUE gas 

furnace, exhaust 

only ventilation

95% AFUE gas 

furnace, exhaust 

only ventilation

95% AFUE gas 

furnace, exhaust 

only ventilation

95% AFUE gas 

furnace, balanced 

ventilation, ducts 

inside conditioned 

space

95% AFUE gas 

furnace, balanced 

ventilation, ducts 

inside conditioned 

space

Cooling (airconditioning

unit)

10 SEER 10 SEER 13 SEER 13 SEER 14.5 SEER 14.5 SEER 16 SEER 16 SEER

Hot Water 50-gal gas, 

EF = 0.53

50-gal gas, 

EF = 0.58

50-gal gas, 

EF = 0.60

50-gal gas, 

EF = 0.60

50-gal gas, 

EF = 0.62

50-gal gas, 

EF = 0.62

Tankless gas, 

EF = 0.94

Tankless gas, 

EF = 0.94
8

SIMPs

Building 

System

1990s 

House

2000s 

House

Standard 

House

Standard 

House with 

Slab Edge 

Insulation

Option 1

Option 1 

with 

Slab Edge 

Insulation

Option 2

Option 2 

with 

Solar 

PV

Lighting and 

Appliances

Gas appliances, 

no ENERGY 

STAR

Gas appliances, 

ENERGY 

STAR, 10% 

fluorescent 

lighting

Gas appliances, 

ENERGY 

STAR, 60% 

fluorescent 

lighting

Gas appliances, 

ENERGY 

STAR, 60% 

fluorescent 

lighting

Gas appliances, 

ENERGY 

STAR, 80% 

fluorescent 

lighting

Gas appliances, 

ENERGY 

STAR, 80% 

fluorescent 

lighting

Gas appliances, 

ENERGY STAR, 

80% fluorescent 

lighting

Gas appliances, 

ENERGY STAR, 

80% fluorescent 

lighting

PV None None None None None None None 1.1-kW system

Source 

Energy Use 202 186 153 139 138 126 113 92

HERS Index 97 89 68 62 60 56 45 37

Estimated 

Annual 

Operating 

Costa

$2,217 $1,968 $1,590 $1,464 $1,435 $1,330 $1,192 $996

Notes: SHGC, solar heat gain coefficient; ACH50, air changes per hour at 50 Pascals; AFUE, annual fuel utilization efficiency; SEER, seasonal energy efficiency 

ratio; EF, energy factor; PV, photovoltaics.

a Utility rates used for the estimated annual operating cost were based on electricity from the City of Roseville and natural gas from

the Pacific Gas and Electric Company, as follows.

Tier 1 –

Up to 500 kWh/month

Tier 2 –

501 to 1,000 kWh/month

Tier 3 –

Greater than 1,000 kWh/month

Electric from City of Roseville ($/kWh) 

including state energy surcharge

$0.1086 $0.1544 $0.1759

Winter Summer

Natural gas from the Pacific Gas and Electric Company 

($/therm)

$0.9878 $1.0229
9

2.1.4 Strategy for Locating Ductwork in Conditioned Space

As a result of the increased benefits in energy savings, Option 2 was chosen for the enclosure 

specification. Then attention turned to location of insulation and air sealing in the attic, as well as 

the specific strategy to ensure placement of the mechanical equipment and ductwork inside 

conditioned space. This was part of a long, iterative design process among the builder, IBACOS, 

and several of the trade contractors, including framing, insulation, and mechanical. A high 

priority for the builder was to use this project as an opportunity to evaluate the most costeffective approach with the fewest design modifications. Table 2 provides a sample of the 

modeling work performed using EnergyGauge USA that IBACOS completed to represent the 

source energy and operational cost savings associated with bringing ductwork inside conditioned 

space. The results show an anticipated source energy savings of 11 MMBtu/yr and 

approximately $116 savings in annual operating costs. Note that the values in Table 2 are not 

directly comparable to the values in Table 1 due to the use of two different modeling programs.

Table 2. Sample of Modeling Results from Mechanical Equipment and Ductwork Location 

Evaluation

Option 2 Package From 

Table 1—Mechanical 

Equipment and 

Ductwork in the Vented 

Attic

Option 2 Package From 

Table 1—Mechanical 

Equipment and 

Ductwork Inside 

Conditioned Space

Source Energy Use 

(MMBtu/yr) 123 112

HERS Index 54 52

Estimated Annual 

Operating Costs $1,274 $1,158

IBACOS has significant experience working with other builder partners in bringing mechanical 

systems and ductwork inside conditioned space through the use of either cathedralized attic 

spaces or dropping bulkheads below the insulated ceiling plane. However, the builder stated that 

neither approach would be acceptable for its product line. Cathedralizing the insulation in the 

attic space (i.e., locating it at the underside of the roof deck rather than along the attic floor) 

would increase the total amount of insulation needed due to the increased surface area that would 

have to be covered, ultimately resulting in higher material costs. Additionally, changing the 

location of the insulation to the roof deck would increase the volume of conditioned space for the 

house but would not add usable square footage for the homeowner. The alternative of bringing 

the equipment and ductwork inside the conditioned space through dropped soffits or bulkheads 

below the ceiling plane was also deemed unacceptable by the builder.

In design meetings with the mechanical and framing trade contractors, the group discussed 

inverting the bulkhead or soffit space that typically would be installed below the ceiling plane 

and instead locating it at the attic floor, as shown in Figure 3 and Figure 4.
10

Figure 3. Mechanical equipment and ductwork within unconditioned space of the vented attic

Figure 4. Mechanical equipment and ductwork within the semiconditioned

bulkhead space at the floor of the vented attic

For the inverted bulkhead approach to be considered for this test house project, the team outlined 

several design parameters that had to be met, including that the redesigned truss not affect the 

bearing location at the footing level. If structural bearing supports had to be relocated, this would 

require an engineer to reevaluate the structural package for the home, and the plans would need 

to be resubmitted to the township for review. In addition, the trusses would need to create an 

unobstructed space to accommodate the largest diameter insulated flexible ductwork that was 
11

anticipated for use, based on the room-by-room heating and cooling load calculations for the 

house. In this case, a 12-in.-diameter duct with R-6 insulation was the largest specified. 

The roof truss manufacturer also participated in the design discussions and was able to provide a 

proposed redesign of the roof truss within the time allotted. By modifying the original design 

(see Figure 5), the proposed design as shown in Figure 6 provided a centrally located chase along 

the floor of the attic. To provide the central bearing location that was consistent with the existing 

structural design for the home, a framing member was dropped from the truss web to bear on the 

interior load-bearing partition wall. Figure 7 shows in plan view the approximate area of the 

cavity created by the new truss design and the ductwork layout. Not all the duct runs terminate 

within the centralized bulkhead. Due to the layout of the girder trusses, the bulkhead area was 

limited to the area shown. To maintain register locations at the ceiling plane, rather than 

dropping down into a high sidewall register (a recommended change for future projects), some 

runs had to penetrate through the side of the bulkhead and extend up to 7 ft outside of it. 

Approximately 15% of the total installed duct length was outside conditioned space; this was not 

accounted for in the final BEopt models because that software does not allow for a fractional 

ductwork location.

Although not all of the ductwork fit in the area of the cavity, care was taken during installation to 

ensure that any ductwork passing out of the cavity (see Figure 8) was well sealed at the 

penetration, and the portions outside the cavity were buried in the full depth of loose-fill 

insulation.

Figure 5. Standard roof truss for the builder’s Plan 4 houses
12

Figure 6. Modified roof truss for the Plan 4 test house, which provides a chase for ductwork at the 

ceiling plane and has 16-in. raised heels along the perimeter
13

Figure 7. Final layout of the centrally located bulkhead and mechanical equipment inside a closet

The outer box represents the extents 

of the centrally located bulkhead at 

the attic floor.

The smaller inner box represents the 

location of the utility closet for 

mechanical equipment within the 

master bedroom closet.
14 

Figure 8. Ductwork centrally distributed within the conditioned space of the bulkhead at the attic 

floor 

2.2 Whole-House Energy Modeling

IBACOS used a combination of REM/Rate and EnergyGauge USA to evaluate the whole-house 

energy consumption of the prototype during the design process. As a result of the design efforts 

outlined in Section 2.1 above, the thermal envelope was changed from the standard 

specifications to include high performance construction features such as 2 in. of slab edge 

insulation, R-15 wall insulation, 16-in. raised heel trusses to accommodate R-38 insulation on the 

attic floor, and higher performing windows. Mechanical equipment with improved rated 

efficiency was incorporated and located in conditioned space via the use of a bulkhead built into 

the roof trusses. Additionally during construction, the decision was made to increase the attic 

insulation to R-49 in areas of the attic with sufficient clearance. Furthermore, the PV system was 

upgraded from the originally specified 1.1-kW system to a 2.4-kW system. These as-built 

specifications were used in BEopt models for BA program purposes. Energy modeling using 

BEopt Version 1.3 was performed based on the specifications for the as-built prototype and the 

builder’s standard shown in Table 3. 
15

Table 3. Comparison of Standard Versus Prototype House Specifications

Component 2011 Builder Standard Prototype House

Concrete Slab Uninsulated R-10 vertical slab edge insulation

Exterior Walls 2 × 4 16-in. o.c. R-13 with 

R-3 sheathing

2 × 4 16-in. o.c R-15 with 

R-3 sheathing

Roof Attic floor R-30 with radiant 

barrier

Attic floor R-49 with radiant 

barrier, with built-in bulkhead to 

accommodate ductwork below 

insulation and raised heel trusses

Exterior Doors R-4 R-4

Windows U = 0.35, SHGC = 0.30 U = 0.28, SHGC = 0.26

Building Airtightness 3.0 ACH50

2.45 ACH50 tested

(1.7 ACH50 target)

Mechanical Ventilation Exhaust only per ASHRAE 

62.2 (ASHRAE 2010a)

AirCycler VS into return duct with 

AirCycler SmartExhaust switch in 

bathrooms

Heating 80-AFUE natural gas furnace 

located in unconditioned attic

95-AFUE natural gas furnace 

located in mechanical closet in 

master bedroom closet

Cooling 13 SEER 16 SEER

Ductwork R-6 in unconditioned space

R-6 in conditioned bulkhead, R-8 

in unconditioned space buried 

under R-49 insulation; 2.4% total 

leakage compared to fan flow 

(measured results)

Water Heater 50-gal gas, EF = 0.6 Tankless gas, EF = 0.94

Appliances ENERGY STAR refrigerator 

and dishwasher

ENERGY STAR refrigerator and 

dishwasher

Fluorescent Lighting 60% 80%

PV None 2.4 kW

% Better than BA 

House Simulation 

Protocols (Hendron and 

Engebrecht 2010)

12.0% 35% without PV, 

60% with PV

BEopt models predicted that the builder’s standard inputs would provide a savings of 11.8% 

relative to the BA House Simulation Protocols (Hendron and Engebrecht 2010), whereas the 

prototype house specifications provided savings of 35% without PV and 60% with PV (both 

relative to the BA House Simulation Protocols) (Hendron and Engebrecht 2010). Figure 9

illustrates this comparison.
16

Figure 9. Output from BEopt source energy modeling by subcategory

2.3 Test Plan Development

After the test house was designed and the modeling was completed, a field test plan was 

developed to answer the research questions that arose during the design development process. 

2.3.1 Research Questions

Research questions for this test house project focused on measuring the performance of the 

proposed space conditioning system and specifically the capacity of the system to maintain 

acceptable levels of indoor temperature and relative humidity. Data were collected on the 

performance of both the equipment and distribution ducts. 

Much resistance to the load calculation, system sizing, and design strategies proposed for this 

test house was encountered in discussions with the heating, ventilation, and air conditioning 

(HVAC) trade contractor and mechanical system designer for this project. Contractors appear to 

be unfamiliar with the centrally located system using compact duct runs that throw air toward 

exterior walls. Thus, the contractors are reluctant to assume the liability of the performance of 

these systems because the systems deviate significantly from their standard system design 

approach. 
17

One of the main goals of the project was to involve the HVAC contractor and the mechanical 

system designer throughout the design, installation, and testing process of the space conditioning 

system to demonstrate to them the cost savings and performance benefits of these types of 

systems. The hope is that they will incorporate these practices into their system designs in the 

future. 

The following questions were developed to be answered via short-term testing and long-term 

monitoring: 

• How effective is the proposed space conditioning system at maintaining Air Conditioning 

Contractors of America (ACCA) Manual RS standards for temperature uniformity 

(Rutkowski 1997) in several rooms of the house: the master bedroom, the kitchen/family 

room, and one additional bedroom?

o What is the difference in temperature in the insulated bulkhead cavity compared 

to the uninsulated attic?

o What are the delivered supply temperatures at each register, and how long after 

system startup does it take for the temperature of the supply air measured at the 

point of delivery (register) to reach the temperature measured at the main plenum?

o How do temperature and relative humidity vary in each measured room from the 

temperature at the thermostat?

- Near a window or sliding door?

- Near an opaque wall?

- In the center of a room?

o What is the temperature distribution in each measured room using ceiling supply 

registers located closer to the center of the house? 

o How do temperature and relative humidity levels vary with system runtime?

o What is the homeowner perception of temperature and relative humidity levels in 

the house? 

• How does the actual measured energy consumption of four major subcategories (heating; 

cooling; hot water; and lighting, appliances, and miscellaneous electric loads) compare to 

the projected energy consumption using BEopt when actual weather and operating 

conditions are normalized? Is there any clear evidence that these differences are due to 

weather, occupant behavior, modeling errors, or system performance issues?

Although answering all of these questions will require long-term monitoring, the following

short-term characterization tests as detailed in Table 4 are necessary to understand the long-term 

results.
18

Table 4. Research Measurements and Equipment for Short-Term Characterization Tests

Measurement Equipment

Building Airtightness Energy Conservatory Blower Door

Duct Airtightness Energy Conservatory Duct Blaster

Room-by-Room Airflows ALNOR LoFlo Balometer 

Air Leakage at Recessed Cans and 

Wall Penetrations Energy Conservatory Pressure Pan

Room-to-Room Pressure Balancing DG-700 manometer

Infrared (IR) Flow Visualization FLIR T400 IR thermal imaging camera

Room Temperature Uniformity 

Measurements

Campbell Scientific CR1000 data logger 

with unshielded thermocouples mounted 

on wooden test stands

Short-term test results are detailed in the following sections. Long-term monitoring will be 

detailed in a future report after at least 1 year of monitored data has been collected.
19

3 Short-Term Tests

3.1 Room-by-Room Supply Register Airflow

3.1.1 Methods

The airflow from each supply register in each room was measured in cooling mode using a 

calibrated low-flow balometer as shown in Figure 10. The readings are documented for 

comparison to the design values for airflow. If necessary, flows can be adjusted and balanced to 

meet the design values through the use of balancing dampers in the ductwork. Flow hood 

measurements at each register will quantify airflow at those registers and will allow a 

comparison to be made against design values and to determine the existence of any potential low 

airflow situations that may affect occupant comfort.

Figure 10. Low-flow balometer testing

3.1.2 Results

Airflow from each supply register in each room was measured in cooling mode using a 

calibrated low-flow balometer. Table 5 lists the results. Variations from design values ranged 

from 1.4% to 110%. Although measured flows for the kitchen/family room area and master 

bedroom were substantially different from the design values, they were still within the ACCA 

Standard 5 requirements of a difference of no more than 20% or 25 CFM (whichever is greater) 

between design and measured flow rates (ACCA 2010). The laundry room was outside these 

limits, with flow 110% (32 CFM) greater than design. Balancing of the flows could not be 

completed due to the location of balancing dampers in the bulkhead space, which at the time of 

flow testing had already been rendered inaccessible by the installation of the ceiling drywall. 

Airflow at the master bathroom was not measured because the register location was overlooked 

during testing. 
20

Table 5. Pressure Balancing Results for Each Room

Location Design 

Airflows

Measured 

Airflows

% of 

Deviation 

from Design

Master Bedroom 229 270 18%

Bedroom 1 93 87 –6%

Bedroom 2 115 107 –7%

Laundry 29 61 110%

Office/Den 71 72 1.4%

Living Room 202 210 4%

Kitchen/Family Room Area 261 311 19%

Master Bathroom 50 – –

3.1.3 Discussion

Although balancing dampers were specified in the HVAC plans and were installed in the test 

house, due to the installation of drywall prior to the installation of the furnace/air-handler unit 

(AHU), the balancing dampers were unable to be used to balance the flow. This is unique to the 

design strategy of creating an airtight box around the ductwork, which rendered the balancing 

dampers inaccessible; however, access to balancing dampers can be difficult in any attic 

installation situation. In the future, if this design strategy of creating an airtight box around 

ductwork to place it inside conditioned space is used, the order of installation must be considered 

to accommodate system balancing, or provisions should be made to facilitate access to the 

dampers in the bulkhead space. The design flows compared to the measured flows indicate a 

68 CFM increase above design airflows, indicating that the proper fan speed had not been 

selected in the furnace/AHU. 

3.2 Duct Air Leakage

3.2.1 Methods

The tightness of the air distribution system was tested with a duct blaster to determine the total 

air leakage in the system and, in conjunction with the blower door test, to determine air leakage 

to the outdoors. The amount of air leakage found will allow the assessment of the performance of 

the capacity of the air distribution system for delivering and drawing air into the house. 

3.2.2 Results

Duct leakage tests were performed to determine total air leakage from the distribution system as 

a percentage of total system airflow. Table 6 shows the results. Duct leakage testing was also 

performed in conjunction with the blower door test to determine the amount of air leakage from 

the ductwork to the outdoors. Duct leakage to the outdoors was relatively low. 

Table 6. Duct Air Leakage Test Results

Performance Metric Results

House Size 2,311-ft2 finished area

Duct Leakage 2.4%
21

3.2.3 Discussion

Duct air leakage was within the CEC 2008 Building Energy Efficiency Standards (CEC 2010), 

validating the measures taken to reduce the duct length and to locate the ductwork within 

conditioned space. 

3.3 Whole-Building Air Leakage

3.3.1 Methods

To evaluate the airtightness performance of the building enclosure, a test using a blower door 

was conducted after the house was completed. The test measured the number of ACH under 

negative pressure for the house, and the test values can be compared to the benchmark values.

An intermediate blower door test (shown in Figure 11) was performed after drywall was installed 

but before trim, floors, and ceiling penetrations were sealed to measure the amount of air leakage 

in the whole house. 

Figure 11. Blower door testing

3.3.2 Results

An intermediate test to measure the house air leakage rate at 50 Pa depressurization was 

conducted when the house was mostly complete, except that all ceiling penetrations were 

unsealed. 

Final testing after sealing all ceiling penetrations revealed an improvement for the completed 

house. Table 7 compares these results to the intermediate test results.
22

Table 7. Characterization Testing: House Leakage

Performance Results

House Size 2,311-ft2 finished area

House Volume 20,799 ft3

Infiltration

Test 1a Final

1,400 cfm50 850 cfm50

4.03 ACH50 2.45 ACH50 a

Prior to trim and sealing of all penetrations but after sheetrock installation

3.3.3 Discussion

Whole-building air leakage improved considerably after air sealing all penetrations through the 

drywall. The final value of 2.45 ACH50 is greater than the target value of 1.7 ACH50. Possible 

reasons for the failure to meet this goal include recessed light fixture and wall penetration 

leakage. Despite attempts made at sealing them, they still showed significant air leakage levels, 

as discussed below in Section 3.4. The exhaust fans also represented a source of air leakage.

Although it was difficult to get a laborer into the attic to perform the air sealing because that 

effort was a new venture, a significant decrease in air leakage was possible. Using two people to 

perform the installation could have sped the installation time to enable one person to move the 

equipment, hose, and light while the other person performed the air sealing. The significant drop 

in air leakage is a result of this sealing process.

3.4 Recessed Light Fixture and Wall Penetration Air Leakage

3.4.1 Methods

Additional testing was conducted during blower door testing to measure air leakage around 

recessed light fixtures and wall penetration air leakage. A pressure pan and digital manometer 

were used to conduct testing at recessed light fixtures, wall outlets, and switches. 

3.4.2 Results

Additional testing was conducted during the blower door testing to document the specific air 

leakage contribution of various penetrations. The insulation-contact-rated airtight recessed light 

fixtures ranged from 2 to 3 CFM each; wall outlets and switches ranged from 1 to 13 CFM each.

3.4.3 Discussion

The recessed light fixture and wall penetration air leakage levels remained significant even after 

air sealing was performed at the junction between the recessed light fixtures to the drywall and 

wire penetrations at the top plates. 

Significant leakage through the outlets and switches remained, both on the interior partition walls 

and exterior walls. No sealing was performed at the switchbox; instead, rigorous air sealing was 

performed at the top plates of the interior walls. Blower door testing indicated that air leakage 

may be occurring to interior partition walls from the exterior wall via penetrations between the 

walls. Also, due to difficulty in accessing the top plate on the exterior wall of the house, sealing 

at this location may have been subpar. Spray foam was applied after the batts had been installed 

on the perimeter, which covered the top plate of the exterior wall that abutted the garage.

Lack of good connection between the drywall in the garage and the bottom plate contributed to 

significant air leakage into the house at that point. 
23

Due to the large number of outlets and switches, as well as low-voltage boxes, the total 

contribution to air leakage of the house was significant.

3.5 Room-to-Room Pressure Balancing

3.5.1 Methods

A digital manometer was used to measure the pressure difference between rooms with the doors 

closed to the central space. Readings were taken with the doors closed and the mechanical 

system operating at each room with transfer grilles over the doors. Readings can be compared to 

the benchmark values. 

3.5.2 Results

Pressure readings were taken with the doors closed and the mechanical system operating. The 

pressure readings between the spaces were within desired results, varying between 0.1 to 0.3 Pa.

3.5.3 Discussion

Pressure differences between individual rooms and the airspace containing the central return 

were acceptably low due to the use of over-the-door pressure relief grilles. 

3.6 Infrared Flow Visualization

3.6.1 Methods

Flow visualization testing using an IR thermal imaging camera was conducted in the master 

bedroom to determine the temperature uniformity of those spaces provided by the compact duct 

system layout and the use of ceiling-mounted supply distribution. 

Infrared cameras “see” the temperatures of surfaces but not air. For the camera to be able to see 

the flow pattern of the air, a “screen” was created from a 6-ft × 9-ft black sheet of felt, mounted 

on two paint-roller extension poles and a shower rod, with sufficient clamps to hold the assembly 

together (see Figure 12). When this black felt screen was placed parallel to the primary flow path 

from the register, its surface temperature responded based on the temperature and flow pattern of 

the air leaving the supply register. Then IR pictures of the felt were taken to visually observe 

flow patterns. Test equipment consisted of an IR camera and the black felt screen assembly.

The purpose of this testing was to observe if flow from the ceiling-mounted registers located 

toward the interior walls could provide sufficient “throw” to ensure that conditioned air reached 

the exterior walls. Flow was observed in both the heating mode and the cooling mode.
24

Figure 12. Black felt IR viewing screen positioned adjacent to an exterior wall and parallel 

to the primary register airflow path

3.6.2 Results

Conditions during the test were clear, 50°F outdoor temperature, and 70°F indoor temperature, 

and the testing was performed between 6:00 p.m. and 8:00 p.m. Because outdoor conditions were 

mild, it was possible to operate the HVAC system in both the heating mode and the cooling 

mode. During the cooling mode, the observed flow behavior from the register indicated that air 

was mixing uniformly upon leaving the register, as shown in Figure 13. 

The flow in heating mode was observed to reach the exterior wall of the room, as shown in 

Figure 14 and Figure 15. Note that the use of a wide range for these two photos prevents sharp 

visual contrast between the hot and cool areas. However, significant stratification was observed, 

with an obvious layer of cooler air extending upward about 4 ft from the floor. Further testing 

was performed in other rooms of the house (see Figure 16 and Figure 17) and revealed behavior 

consistent with that observed in the master bedroom. These measurements were taken by IR 

photographing of the walls of the house, revealing a clear pattern of stratification.

To help determine the cause of this behavior, IR photography during heating system operation 

also was measured in a nearby house built to the builder’s typical practices with respect to the 

construction of the thermal enclosure and the placement of the HVAC registers. Both houses 

shared the same floor plan and orientation, and testing was performed after dark. Observations 

from the house built to the builder’s typical standard showed the same behavior. No black felt 

setup was required in the nearby house because taking an IR picture of the walls was sufficient to 

observe the stratification.
25

Research conducted by Straub (1957) indicates that this behavior is due to the ceiling location of 

the registers, along with the supply temperatures associated with a typical forced-air, fuel-fired 

space heating system. If supply temperatures were closer to the temperature of the air in the 

room, less stratification would be observed. Straub (1957) recommends that supply temperatures 

for ceiling registers be no greater than 100°F to prevent stratification similar to that observed at 

the Roseville test house.

Figure 13. IR photo of black felt screen during cooling system operation (temperature scale in °F)
26

Figure 14. IR photo of black felt screen during heating system operation (temperature scale in °F)

Figure 15. IR photo of black felt screen shortly after system turnoff, clearly showing stratification 

(temperature scale in °F)
27

Figure 16. IR photo showing vertical stratification (temperature scale in °F)

Figure 17. IR photo showing uniform horizontal distribution of heated air (temperature scale in °F)
28

3.6.3 Discussion

The use of modern IR equipment in an as-built house was able to confirm observations made by 

researchers 56 years ago. High supply temperatures from ceiling registers result in the separation 

of the warm and cool layers of air in the room and insufficient mixing. This is true regardless of 

the register placement, as verified by testing houses with the experimental register placement 

toward the interior of the room and the builder’s standard placement toward the exterior wall.

Temperature stratification observed via IR photography during and after heating system 

operation indicated a difference of approximately 7°F (3.9°C) between the head and ankles of a

standing occupant. According to ASHRAE Standard 55, this house would fall into Class C of 

Section 5.2.4.3 Vertical Temperature Difference, and approximately 15% of the occupants would 

be dissatisfied (ASHRAE 2010b).

The results of this test would have been optically superior if a smaller fixed range had been used 

on the IR camera. Given the placement of the camera relative to the supply register and black felt 

assembly, an upper temperature of 90°F (32°C) may have been sufficient and would have 

provided superior contrast in the images. The use of autorange provides a sharper contrast but 

results in difficulty in comparison of images later.

3.7 In-Room Temperature Uniformity Measurements

3.7.1 Methods

The performance of the ceiling-mounted supply registers located toward the interior of the house 

also was evaluated by taking temperature measurements at five critical locations throughout the 

master bedroom and six locations throughout the kitchen/family room area, including the supply 

air temperature and the room air near the window, near the opaque exterior wall, in the center of 

the room, and near an interior partition wall (see Figure 18).
29

Figure 18. Layout of temperature measurements

Temperature was measured using thermocouples mounted 43 in. above the FF using test stands 

made of wooden dowel rods inserted into an “x” base (see Figure 19). The temperature 

measurements consisted of thermocouple wire with ends twisted together (a junction) at the 

measurement point and the other end of the wire connected to a data logger, sampling every 20 s 

and averaging every minute and hour. Temperature measurements were conducted for an 11-h 

period over 1 night. Furnace and AHU runtime was not directly measured via electrical 
30

measurements during this time due to sensor malfunction. However, runtime was obtained 

indirectly using the temperature measured at the supply register, which increased dramatically 

during furnace operation.

Figure 19. Sensor stands and a supply register in the kitchen/family room area

3.7.2 Results

During the 11-h test, the outdoor temperature ranged from 48.0° to 39.9°F. The indoor 

temperature measured at the thermostat ranged from 71.6° to 72.5°F, and the furnace ran 

39 times.

Results showed temperatures within ±5.4°F throughout the kitchen/family room area and ±1.8°F 

throughout the master bedroom. The only large variation in temperature was because two sensors 

in the kitchen/family room area were hit directly by the flow of heated air provided by the 

register. The most affected sensor (T_Nook_Avg) was part of the long-term monitoring 

equipment. Located at the same height as all other sensors (43 in. above FF) on an interior 
31

partition wall near the exterior wall and approximately 10 ft horizontally from the register, its 

intended purpose was to measure the conditions near the exterior wall. Although it was 

unintentional that this sensor was hit by the register airflow, it is indicative of the ability of 

conditioned air to reach the exterior wall. Figure 20 shows an example of the variation observed 

in sensor locations in the kitchen/family room area during the course of a typical hour when three 

heating cycles occurred. The temperature measurements in the master bedroom did not display 

this behavior (see Figure 21) because their locations were not directly in line with the airstream 

from the heating supply register. Ignoring this behavior, intraroom variation in temperature in the 

kitchen/family room area was within 1.8°F (1.0°C).

The maximum temperature of air leaving the heating register was 118°F (48.0°C). Cyclical 

behavior observed in Figure 20 and Figure 21 was consistent throughout the 11-h test period.

Figure 20. Temperatures (°C) at various sensor locations in the 

kitchen/family room area during 1 h

20

21

22

23

24

25

26

27

0:000:100:200:300:400:50

Temperature (°C)

Time (Hour:Minute)

T_Family_Window

T_Kitchen_Center

T_Family_ExtWall

T_Family_Center

T_Kitchen_Avg

T_Nook_Avg

T_Thermostat_Avg
32

Figure 21. Temperatures (°C) at various sensor locations in the master bedroom during 1 h

3.7.3 Discussion

The purpose of these measurements was to determine the ability of the distribution system to 

maintain uniform temperatures throughout the air space of two observed rooms. The results show 

that the measurements did this successfully. Although the room air temperature was uniform 

when the impact of the heating system operation was ignored, the reality is that occupants in 

those locations at those times of system operation would experience those disruptions. It is 

important to remember that, although the heating system is responsible for eliminating large 

trends in temperature difference over time, it does this by causing small but substantial 

disruptions in temperature at regular intervals.

20

21

22

23

24

25

26

27

0:000:100:200:300:400:50

Temperature (°C)

Time (Hour:Minute)

T_Master_ExtWin

T_Master_ExtWall

T_Master_Center

T_Mast_Bed_SW_Avg

T_Mast_Bed_SE_Avg

T_Thermostat_Avg
33

4 Conclusions

As a result of the builder, design consultant, and trades working collaboratively to identify a 

package of measures satisfying the requirements of the CEC 2008 Building Energy Efficiency 

Standards (CEC 2010) and to prepare for the proposed 2013 CEC code and ENERGY STAR 

Version 3.0 requirements, the test house constructed in Roseville, California, has a modeled 

energy savings of 60% with respect to the BA House Simulation Protocols (Hendron and 

Engebrecht 2010). The energy improvements were implemented without requiring changes to the 

drawings that would have impacted local code or zoning approval. 

Short-term testing results showed that duct air leakage was low, as anticipated, due to the short 

duct runs and the placement of the ductwork in conditioned space. However, one problem 

foreseen during planning was realized during commissioning, where the lack of access for 

servicing the ductwork and dampers in the bulkhead area prevented retroactive balancing of 

individual branches, resulting in significant differences between specified and measured airflow 

values for some duct runs. The results of thermal imaging performed for the house when 

operating in heating and cooling modes showed that the alternative register placement in the test 

house provided equivalent horizontal distribution to the builder’s standard house. The tests 

validated historical stratification issues of ceiling supply registers with high supply air 

temperatures.

Research questions will continue to be addressed through the data gathered by the long-term 

monitoring equipment and will be reported at the end of the testing period. 
34

5 References

ACCA (2010). ANSI/ACCA Standard 5 QI-2010: HVAC Quality Installation Specification—

Residential and Commercial Heating, Ventilating, and Air Conditioning (HVAC) Applications.

Arlington, VA: ACCA.

ASHRAE (2010a). ANSI/ASHRAE Standard 62.2 – 2010, Ventilation and Acceptable Indoor Air 

Quality in Low-Rise Residential Buildings. Atlanta, GA: ASHRAE.

ASHRAE (2010b). ANSI/ASHRAE Standard 55-2010, Thermal Environmental Conditions for 

Human Occupancy. Atlanta, GA: ASHRAE.

California Building Standards Commission (2007). 2007 California Building Code, Title 24.

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CEC (2010). 2008 Building Energy Efficiency Standards: Residential Compliance Manual. 

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