NISTIR 7238

Investigation of the Impact of

Commercial Building Envelope

Airtightness on HVAC Energy Use

Steven J. Emmerich

Tim McDowell

Wagdy Anis
NISTIR 7238

Investigation of the Impact of

Commercial Building Envelope

Airtightness on HVAC Energy Use

Steven J. Emmerich

Building and Fire Research Laboratory

Timothy P. McDowell

TESS, Inc.

Wagdy Anis

Shepley Bulfinch Richardson and Abbott

Prepared for:

U.S. Department of Energy

Office of Building Technologies

June 2005

U.S. Department of Commerce

Carlos M. Gutierrez, Secretary

Technology Administration

Phillip J. Bond, Under Secretary of Commerce for Technology

National Institute of Standards and Technology

Hratch Semerjian, Acting Director
ABSTRACT 

This report presents a simulation study of the energy impact of improving envelope airtightness 

in U.S. commercial buildings. Despite common assumptions, measurements have shown that 

typical U.S. commercial buildings are not particularly airtight. Past simulation studies have 

shown that commercial building envelope leakage can result in significant heating and cooling 

loads. To evaluate the potential energy savings of an effective air barrier requirement, annual 

energy simulations were prepared for three nonresidential buildings (a two-story office building, 

a one-story retail building, and a four-story apartment building) in 5 U.S. cities. A coupled 

multizone airflow and building energy simulation tool was used to predict the energy use for the 

buildings at a target tightness level relative to a baseline level based on measurements in existing 

buildings. Based on assumed blended national average heating and cooling energy prices, 

predicted potential annual heating and cooling energy cost savings ranged from 3 % to 36 % with 

the smallest savings occurring in the cooling-dominated climates of Phoenix and Miami. In order 

to put these estimated energy savings in context, a cost effectiveness calculation was performed 

using the scalar ratio methodology employed by ASHRAE SSPC 90.1. 

Keywords: energy efficiency, infiltration, office buildings, ventilation 

iii 
TABLE OF CONTENTS 

ABSTRACT iii 

INTRODUCTION 1 

ANALYSIS METHOD 2 

BUILDING DESCRIPTIONS 3 

AIRFLOW MODELS 16 

SYSTEM MODELS 18 

SCALAR CALCULATION 19 

RESULTS 21 

DISCUSSION 34 

ACKNOWLEDGEMENTS 35 

REFERENCES 36 

Appendix A: Commercial Building Airtightness Data 39

iv
1
Introduction 

The objective of this study is to investigate the impact of envelope airtightness on the energy consumption 

of typical commercial buildings in the U.S. Despite common assumptions that envelope air leakage is not

significant in office and other commercial buildings, measurements have shown that these buildings are 

subject to larger infiltration rates than commonly believed (Persily 1998, Proskiw and Phillips 2001). 

Infiltration in commercial buildings can have many negative consequences, including reduced thermal 

comfort, interference with the proper operation of mechanical ventilation systems, degraded indoor air 

quality, moisture damage of building envelope components, and increased energy consumption. For these 

reasons, attention has been given to methods of improving airtightness both in existing buildings and new 

constructions (Persily 1993). Since 1997, the Building Environment and Thermal Envelope Council of the 

National Institute of Building Sciences has sponsored several symposia in the U.S. on the topic of air 

barriers for buildings in North American climates. Canada Mortgage and Housing Corporation has 

sponsored similar conferences in Canada. Others have also published articles on the importance of air 

leakage in commercial buildings (Anis 2001, Ask 2003). However, the focus of these conferences and 

publications has largely been air barrier technology and the non-energy impacts of air leakage in buildings. 

In order to evaluate the cost effectiveness of such measures to tighten buildings, estimates of the impact of

air leakage on energy use are needed. 

An earlier study estimated the national impact of infiltration in office buildings based on a simplified

method for calculating both the infiltration flows and the building energy use (Emmerich et al. 1995). The 

loads were calculated for a set of 25 buildings, each representing a certain percentage of the total office 

building stock of the United States. Twenty of these buildings represent the existing office building stock as 

of 1979 (Briggs, Crawley, and Schliesing 1992) and five represent construction between 1980 and 1995 

(Crawley and Schliesing 1992). Further work improved on this initial method by using airflows from multizone airflow simulations (Emmerich and Persily 1998) combined with a simple load calculation. More 

recently, a more detailed analysis method to determine the impact of infiltration and ventilation rates on 

building energy usage was developed (McDowell et al. 2003). This approach included the coupling of a 

detailed multi-zone airflow model based on the CONTAMW model (Dols and Walton 2002) and the 

detailed multi-zone building energy modeling program TRNSYS (Klein 2000). This project demonstrated 

the ability of the coupled programs to study the annual heating and cooling energy use in the US office 

building stock as a function of infiltration and ventilation rates. 

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Standard 

90.1 Envelope Subcommittee has formed a task group to consider updating the building air leakage 

requirements in the standard to require a continuous air barrier system. An air barrier system is the 

combination of interconnected materials, flexible joint systems, and components of the building envelope 

that provide the air-tightness of the building. Included in the current standard are detailed quantitative 

limits for air leakage through fenestration and doors but only general qualitative guidance for the opaque 

portion of the building envelope (ASHRAE 2001b). For example, the Standard requires sealing, caulking, 

gasketing, or weather-stripping such locations as joints around fenestration and doors, junctions between 

floors, walls, and roofs, etc. However, there is no quantitative air leakage limit specified for either the wall 

and other envelope components or the building as a whole. This is analogous to requiring that care be taken 

when installing insulation without requiring any minimum R-value. 

1 
Analysis Method

To provide input to the ASHRAE 90.1 Envelope Subcommittee in its consideration of the potential energy 

savings and cost effectiveness of an effective air barrier requirement, annual energy simulations and cost

estimates were prepared for three common, modern nonresidential buildings – a two-story office building, a 

one-story retail building, and a four-story apartment building. The apartment building is included because 

the scope of Standard 90.1 includes multi-family structures of more than three stories above grade. The 

new combined airflow-building energy modeling tool (described by McDowell et al. 2003) was used to

estimate the energy impact of envelope airtightness in multiple U.S. climate types. HVAC systems 

representative of the types used in these buildings were included in the building models. Other building

model parameters were chosen such that the buildings would be considered typical new construction and 

meet current ASHRAE Standard 90.1 requirements. 

Energy simulations were performed using TRNSYS (Klein 2000) - a transient system simulation program

with a modular structure that was designed to solve complex energy system problems by dividing the 

problem into a series of smaller components. Each of these components can then be solved independently

and coupled with other components to simulate and solve the larger system problem. Components (or 

Types as they are called) in TRNSYS may be as simple as a pump or pipe, or as complicated as a multizone building model. The entire program is then a collection of energy system component models grouped 

around a simulation engine (solver). The modular nature of the program makes it easier to add content to

the program by introducing new component models to the standard package. The simulation engine 

provides the capability of interconnecting system components in any desired manner, solving differential 

equations, and facilitating inputs and outputs. The TRNSYS multi-zone building model (called Type 56) 

includes heat transfer by conduction, convection and radiation, heat gains due to the presence of occupants 

and equipment, and the storage of heat in the room air and building mass. 

The infiltration in the buildings was modeled using a TRNSYS type based on an updated version of the 

AIRNET model (Walton 1989), which is included in the multizone airflow and contaminant dispersal 

program CONTAMW (Dols and Walton 2002). CONTAMW combines the best available algorithms for 

modeling airflow and contaminant transport in multizone buildings with a graphic interface for data input 

and display of results. The multizone approach is implemented by constructing a network of elements 

describing the flow paths (HVAC ducts, doors, windows, cracks, etc.) between the zones of a building. The 

network nodes represent the zones, each of which are modeled at a uniform temperature and pollutant 

concentration. The pressures vary hydrostatically, so the zone pressure values are a function of the 

elevation within the zone. The network of equations is then solved at each time step of the simulation. 

McDowell et al. (2003) described the coupling of the TRNSYS and CONTAM models. 

Simulations of annual energy use were run using TMY2 files (Marion and Urban 1995) for five different

cities representing different climate zones of the US (Miami, Phoenix, St. Louis, Bismarck, and

Minneapolis) and at three levels of airtightness representing different construction practices. The levels of 

airtightness were selected to represent 1) no air barrier, 2) target air barrier, and 3) best achievable levels

through a review of measured commercial building airtightness data (Persily 1998), ASHRAE Handbook 

data (ASHRAE 2001c) and other sources. Each building was modeled once with frame construction and 

then masonry construction. Thus, the matrix of simulations is 3 building types X 2 envelope construction 

types X 3 airtightness levels X 5 climates, for a total of 90 simulation cases. 

2 
Building Descriptions 

This section describes the three buildings modeled in the study. 

Thermal Properties, Setpoints, and Schedules 

The building models were developed so that the wall constructions and windows would satisfy the 

requirements of ASHRAE Standard 90.1 (ASHRAE 90.1-2001b) for the different locations as described 

below. 

Office Building 

The building modeled is a two story office building with a total floor area of 2250 m2 (24,200 ft2) and a 

floorplan as shown in Figure 1. The building has a window-to-wall ratio of 0.2 with a floor-to-floor height

of 3.66 m (12 ft), broken up between a 2.74 m (9 ft) occupied floor and a 0.92 m (3 ft) plenum per floor. 

The building also includes a single elevator shaft. 

igure 1 Floorplan of two-story office building 

odeling the office building are summarized 

l, roof, slab and window thermal properties for office building 

ix Thickness Conductivity Density Specific Heat Resistance 

4.6 m Floor Plenum

33.5 m

24.4 m

B

L R

F

I

E

4.6 m 4.6 m

4.6 m

3.0 m

P

E

0.9 m

2.7 m

Plenum

Plenum

Floor 1

Floor 2

2.7 m

0.9 m

F, R, B, L are the front, right, back, and left perimeter zones.

I is the core zone. E is the elevator zone.

F

The wall, roof, slab and window thermal properties used for m

in Table 1. 

Table 1 Wal

Frame Wall Construction:

St. Louis, Miami and Phoen

Description m 

(ft)

W/m-K

(Btu/hr-ft-F) (Btu/lb-F) (h )

kg/m3

(lb/ft3

)

kJ/kg-K m2

-K/W

r-ft

2

-F/Btu

Face brick 0.092 

(0.302) (0.508) (0.59) 

0.879 1922 

(120) 

0.921 

(0.22) 

0.10 

Vertical wall air layer

 (0.89) 

0.16 

Gypsum board 0.0127 

(0.0417) 

0.160 

(0.0926) 

800 0.837 

(50) (0.2) 

0.079 

(0.45) 

Steel studs w/mineral wool insulation, R13 0.089 

(0.292) 

0.0751 

(0.0434) 

288 

(18) 

1.298 

(0.31) 

1.2 

(6.7) 

Gypsum board 

(0.0521) (0.0926) 

0.0159 0.160 800 

(50) 

0.837 

(0.2) 

0.099 

(0.56) 

3 
Bismarck and Minneapolis: Thickness Conductivity Density Specific Heat Resistance 

Description 

m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2-K/W

(hr-ft2-F/Btu)

Face brick 0.092 

(0.302) 

0.879 

(0.508) 

1922 

(120) 

0.921 

(0.22) 

0.10 

(0.59) 

Vertical wall air layer 0.16 

(0.89) 

Gypsum board 0.0127 

(0.0417) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.079 

(0.45) 

Steel studs w/mineral wool/fiber batt R13 

0.089 

(0.292) 

0.0751 

(0.0434) 

288 

(18) 

1.298 

(0.31) 

1.2 

(6.7) 

Expanded polystyrene, extruded 

0.0191 

(0.0625) 

0.0277 

(0.016) 

29 

(1.8) 

1.214 

(0.29) 

0.70 

(4.0) 

Gypsum board 0.0159 

(0.0521) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.099 

(0.56) 

Masonry Wall Construction:

St. Louis Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3

)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Face brick 0.092 

(0.302) 

0.879 

(0.508) 

1922 

(120) 

0.921 

(0.22) 

0.10 

(0.59) 

Vertical wall air layer 0.16 

(0.89) 

Hollow medium weight concrete block 

0.203 

(0.667) 

0.779 

(0.450) 

1842 

(115) 

0.837 

(0.2) 

0.26 

(1.48) 

Expanded polystyrene, extruded 

0.0254 

(0.0833) 

0.0277 

(0.016) 

29 

(1.8) 

1.214 

(0.29) 

0.88 

(5.0) 

Gypsum board 0.0159 

(0.0521) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.099 

(0.56) 

Bismarck and Minneapolis Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3

)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Face brick 0.092 

(0.302) 

0.879 

(0.508) 

1922 

(120) 

0.921 

(0.22) 

0.10 

(0.59) 

Vertical wall air layer 0.16 

(0.89) 

Hollow medium weight concrete block 

0.203 

(0.667) 

0.779 

(0.450) 

1842 

(115) 

0.837 

(0.2) 

0.26 

(1.48) 

Expanded polystyrene, extruded 

0.0508 

(0.1667) 

0.0277 

(0.016) 

29 

(1.8) 

1.214 

(0.29) 

1.76 

(10.0) 

Gypsum board 0.0159 

(0.0521) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.099 

(0.56) 

4 
Miami and Phoenix Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2-K/W

(hr-ft2-F/Btu)

Face brick 0.092 

(0.302) 

0.879 

(0.508) 

1922 

(120) 

0.921 

(0.22) 

0.10 

(0.59) 

Vertical wall air layer 0.16 

(0.89) 

Hollow medium weight concrete block 

0.203 

(0.667) 

0.779 

(0.450) 

1842 

(115) 

0.837 

(0.2) 

0.26 

(1.48) 

Gypsum board 0.0159 

(0.0521) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.099 

(0.56) 

Roof Construction:

All Locations Thickness Conductivity Density Specific Heat Resistance 

Description 

m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Built-up roofing 0.0095 

(0.0313) 

1.63 

(0.939) 

1120 

(70) 

1.47 

(0.35) 

0.058 

(0.33) 

Polyisocyanurate insulation 0.0634 

(0.208) 

0.0242 

(0.014) 

24 

(1.5) 

1.59 

(0.38) 

2.62 

(14.85) 

Vegetable Fiber Board Sheathing 

0.0128 

(0.042) 

0.0554 

(0.032) 

288 

(18) 

1.298 

(0.31) 

0.23 

(1.32) 

Slab Construction:

All Locations Thickness Conductivity Density Specific Heat Resistance 

Description 

m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2-K/W

(hr-ft2

-F/Btu)

Concrete normal weight

0.127 

(0.4167) 

1.31 

(0.7576) 

2240 

(140) 

0.837 

(0.2) 

0.097 

(0.55) 

Window:

U-value SHGC

Location 

W/m2

-K 

(Btu/hr-ft2

-F) 

St. Louis, Bismarck, and Minneapolis 3.24 

(0.57) 0.39 

Miami and Phoenix 6.93 

(1.22) 0.25

The internal gains for the occupied spaces are divided into three parts: lighting, receptacle loads, and 

occupants. These gains are all applied using a peak value and fraction of peak schedule. The lighting peak 

is 10.8 W/m2

 (1.0 W/ft2), the peak receptacle load is 6.8 W/m2 (0.63 W/ft2), and the peak occupant density

is 53.4 persons/1000 m2

 (5 persons/1000 ft2). The fraction of peak schedules are shown in Figures 2 to 4. 

The thermostats operate on a setpoint with setback/setup basis. The heating setpoint is 21.1 °C (70 °F) with

a setback temperature of 12.8 °C (55 °F) and the cooling setpoint is 23.9 °C (75 °F) with a setup

temperature of 32.2 °C (90 °F). The schedule for the setback/setup differs between weekdays (hours from

6 to 20 at setpoint), Saturdays (hours from 7 to 14 at setpoint) and Sundays (always at setup/setback). 

However, for the first hour of operation at setpoint, the system does not bring any outdoor air into the zone. 

This hour is prior to building occupancy and is used to bring the zone back to setpoint from the 

setup/setback temperature. 

5 
0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour of Day

Fraction of Peak Occupancy

Weekday

Saturday

Sunday

Figure 2 Fractional occupancy schedule for office 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour of Day

Fraction of Peak Lighting

Weekday

Saturday

Sunday

Figure 3 Fractional lighting schedule for office 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour of Day

Fraction of Peak Receptacle Load

Weekday

Saturday

Sunday

Figure 4 Fractional receptacle load schedule for office 

6 
Retail Building 

The retail building modeled in this study is a one-story building with a total floor area of 1125 m2 (12,100 

ft2

) and a floorplan as shown in Figure 5. The building has a window-to-wall ratio of 0.1 with a floor-tofloor height of 3.9 m (13 ft), broken up between a 3.0 m (10 ft) occupied floor and a 0.9 m (3 ft) plenum

per floor. 

igure 5 Floorplan of one-story retail building 

he wall, roof, slab and window thermal properties used in modeling the retail building are summarized in

all, roof, slab and window thermal properties for retail building 

ix Thickness Conductivity Density Specific Heat Resistance 

4.6 m Floor Plenum

33.5 m

24.4 m

B

L R

F

I

4.6 m 4.6 m

4.6 m

P

Plenum

Floor 1 3.0 m

0.9 m

F, R, B, L are the front, right, back, and left perimeter zones.

I is the core zone.

F

T

Table 2. 

Table 2 W

Frame Wall Construction:

St. Louis, Miami and Phoen

Description m 

(ft)

W/m-K

(Btu/hr-ft-F) (Btu/lb-F) (h )

kg/m3

(lb/ft3)

kJ/kg-K m2

-K/W

r-ft

2

-F/Btu

Face brick 0.092 

(0.302) (0.508) (0.59) 

0.879 1922 

(120) 

0.921 

(0.22) 

0.10 

Vertical wall air layer

(0.89) 

0.16 

Gypsum board 0.0127 

(0.0417) 

0.160 

(0.0926) 

800 0.837 

(50) (0.2) 

0.079 

(0.45) 

Steel studs w/mineral wool/fiber batt R-13 (8.06) 

0.089 

(0.292) 

0.0627 

(0.0362) 

9.6 

(0.6) 

0.837 

(0.2) 

1.42 

Gypsum board 0.0159 

(0.0521) (0.0926) 

0.160 800 

(50) 

0.837 

(0.2) 

0.099 

(0.56) 

7 
Bismarck and Minneapolis Thickness Conductivity Density Specific Heat Resistance 

Description 

m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2-K/W

(hr-ft2-F/Btu)

Face brick 0.092 

(0.302) 

0.879 

(0.508) 

1922 

(120) 

0.921 

(0.22) 

0.10 

(0.59) 

Vertical wall air layer 0.16 

(0.89) 

Gypsum board 0.0127 

(0.0417) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.079 

(0.45) 

Steel studs w/mineral wool/fiber batt R-13

0.089 

(0.292) 

0.0627 

(0.0362) 

9.6 

(0.6) 

0.837 

(0.2) 

1.42 

(8.06) 

Expanded polystyrene, extruded 

0.0191 

(0.0625) 

0.0277 

(0.016) 

29 

(1.8) 

1.214 

(0.29) 

0.70 

(4.0) 

Gypsum board 0.0159 

(0.0521) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.099 

(0.56) 

Masonry Wall Construction:

St. Louis Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3

)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Face brick 0.092 

(0.302) 

0.879 

(0.508) 

1922 

(120) 

0.921 

(0.22) 

0.10 

(0.59) 

Vertical wall air layer 0.16 

(0.89) 

Hollow medium weight concrete block 

0.203 

(0.667) 

0.779 

(0.450) 

1842 

(115) 

0.837 

(0.2) 

0.26 

(1.48) 

Expanded polystyrene, extruded 

0.0254 

(0.0833) 

0.0277 

(0.016) 

29 

(1.8) 

1.214 

(0.29) 

0.88 

(5.0) 

Gypsum board 0.0159 

(0.0521) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.099 

(0.56) 

Bismarck and Minneapolis Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3

)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Face brick 0.092 

(0.302) 

0.879 

(0.508) 

1922 

(120) 

0.921 

(0.22) 

0.10 

(0.59) 

Vertical wall air layer 0.16 

(0.89) 

Hollow medium weight concrete block 

0.203 

(0.667) 

0.779 

(0.450) 

1842 

(115) 

0.837 

(0.2) 

0.26 

(1.48) 

Expanded polystyrene, extruded 

0.0508 

(0.1667) 

0.0277 

(0.016) 

29 

(1.8) 

1.214 

(0.29) 

1.76 

(10.0) 

Gypsum board 0.0159 

(0.0521) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.099 

(0.56) 

8 
Miami and Phoenix Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2-K/W

(hr-ft2-F/Btu)

Face brick 0.092 

(0.302) 

0.879 

(0.508) 

1922 

(120) 

0.921 

(0.22) 

0.10 

(0.59) 

Vertical wall air layer 0.16 

(0.89) 

Hollow medium weight concrete block 

0.203 

(0.667) 

0.779 

(0.450) 

1842 

(115) 

0.837 

(0.2) 

0.26 

(1.48) 

Gypsum board 0.0159 

(0.0521) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.099 

(0.56) 

Roof Construction:

All Locations Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Modified bitumen mineral surface roofing 

0.0063 

(0.0208) 

0.109 

(0.063) 

1120 

(70) 

1.47 

(0.35) 

0.058 

(0.33) 

Vegetable fiber board coverboard 

0.0128 

(0.042) 

0.0554 

(0.032) 

288 

(18) 

1.298 

(0.31) 

0.23 

(1.32) 

Polyisocyanurate insulation – aged value 

0.0634 

(0.208) 

0.0312 

(0.018) 

24.0 

(1.5) 

1.59 

(0.38) 

2.42 

(13.75) 

Slab Construction:

All Locations Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2-K/W

(hr-ft2

-F/Btu)

Concrete normal weight 0.127 

(0.4167) 

1.31 

(0.7576) 

2240 

(140) 

0.837 

(0.2) 

0.097 

(0.55) 

Window:

U-value SHGC

Location 

W/m2

-K 

(Btu/hr-ft2

-F)

St. Louis 3.24 

(0.57) 0.39

Bismarck and Minneapolis 

3.24 

(0.57) 0.49 

Miami and Phoenix 6.93 

(1.22) 0.25 

The internal gains for the occupied spaces are divided into three parts: lighting, receptacle loads, and 

occupants. These gains are all applied using a peak value and fraction of peak schedule. The lighting peak 

is 16.15 W/m2

 (1.5 W/ft2), the peak receptacle load is 2.58 W/m2 (0.24 W/ft2), and the peak occupant

density is 162 persons/1000 m2

 (15 persons/1000 ft2). The fraction of peak schedules are shown in Figures 

6 to 8. 

The thermostats operate on a setpoint with setback/setup basis. The heating setpoint is 21.1 °C (70 °F) with

a setback temperature of 12.8 °C (55 °F) and the cooling setpoint is 23.9 °C (75 °F) with a setup

temperature of 37.2 °C (99 °F). The schedule for the setback/setup differs between weekdays (hours from 7 

to 21 at setpoint), Saturdays (hours from 7 to 21 at setpoint) and Sundays (hours from 9 to 19 at setpoint). 

However for the first hour of operation at setpoint the system does not bring any outdoor air into the zone. 

9 
This hour is prior to building occupancy and is used to bring the zone back to setpoint from the 

setup/setback temperature. 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour of Day

Fraction of Peak Occupancy

Weekday

Saturday

Sunday

Figure 6 Fractional occupancy schedule for retail

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour of Day

Fraction of Peak Lighting

Weekday

Saturday

Sunday

Figure 7 Fractional lighting schedule for retail

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour of Day

Fraction of Peak Receptacle Load

Weekday

Saturday

Sunday

Figure 8 Fractional receptacle load schedule for retail 

10 
Residential Building 

The residential building modeled in this study is a four story building with a total floor area of 3425 m2

(36,864 ft2

) and a floorplan as shown in Figure 9. The building has a window-to-wall ratio of 0.25 with a 

floor-to-floor height of 3.0 m (10 ft), broken up between a 2.4 m (8 ft) occupied floor and a 0.6 m (2 ft) 

plenum for the bottom three floors and a 2.4 m (8 ft) occupied floor and a 3.0m (10 ft) attic at the top. The 

attic has a pitched roof and is vented. The building also includes a single elevator shaft with two elevators. 

The corner units will have a doorway connecting to the corridor. One of bottom mid-units is used as a 

lobby entrance instead of a living unit.

9.8 m

6.1m

3.0m E

Unit BL Unit BM Unit BR

Unit LM

Corridor

Unit RM

Unit FL Unit FM Unit FR

9.8 m 9.8 m

9.8 m

9.8 m

9.8 m

9.8 m

6.1m

3.0m E

Plenum BL Plenum BM Plenum BR

Plenum LM

Core Plenum

Plenum RM

Plenum FL Plenum FM Plenum FR

9.8 m 9.8 m

9.8 m

9.8 m

9.8 m

Ceiling Space

Floor 3

Ceiling Space

Floor 2

Ceiling Space

Floor 1

Floor 4

Attic

2.4 m

0.6 m

2.4 m

0.6 m

2.4 m

0.6 m

2.4 m

3.0 m

Figure 9 Floorplan of modeled four-story residential building 

The wall, roof, slab and window thermal properties used for modeling the apartment building are 

summarized in Table 3. 

11 
Table 3 Wall, roof, slab and window thermal properties for apartment building 

Brick Walls Construction:

Bismarck and Minneapolis Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3

)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Face brick 0.092 

(0.302) 

0.879 

(0.508) 

1922 

(120) 

0.921 

(0.22) 

0.10 

(0.59) 

Vertical wall air layer 0.16 

(0.89) 

Extruded polystyrene foam insulating 

sheathing 

0.0191 

(0.0625) 

0.0294 

(0.017) 

28.8 

(1.8) 

1.21 

(0.29) 

0.66 

(3.75) 

OSB sheathing 0.0127 

(0.042) 

0.0917 

(0.053) 

288 

(18) 

1.30 

(0.31) 

0.139 

(0.79) 

Wood studs w/ batt R-13 0.089 

(0.292) 

0.0485 

(0.028) 

73.4 

(4.58) 

0.837 

(0.2) 

1.82 

(10.34) 

Gypsum board 0.0127 

(0.042) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.079 

(0.45) 

St Louis, Miami, Phoenix Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3

)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Face brick 0.092 

(0.302) 

0.879 

(0.508) 

1922 

(120) 

0.921 

(0.22) 

0.10 

(0.59) 

Vertical wall air layer 0.16 

(0.89) 

OSB sheathing 0.0127 

(0.042) 

0.0917 

(0.053) 

288 

(18) 

1.30 

(0.31) 

0.139 

(0.79) 

Wood studs w/ batt R-13 0.089 

(0.292) 

0.0485 

(0.028) 

73.4 

(4.58) 

0.837 

(0.2) 

1.82 

(10.34) 

Gypsum board 0.0127 

(0.042) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.079 

(0.45) 

Clapboard Wall Construction:

Bismarck and Minneapolis Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3

)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Wood fiber-cement clapboards 

0.0634 

(0.208) 

0.171 

(0.099) 

1922 

(120) 

1.00 

(0.24) 

0.037 

(0.21) 

Extruded polystyrene foam insulating 

sheathing 

0.0191 

(0.0625) 

0.0294 

(0.017) 

28.8 

(1.8) 

1.21 

(0.29) 

0.66 

(3.75) 

OSB sheathing 0.0127 

(0.042) 

0.0917 

(0.053) 

288 

(18) 

1.30 

(0.31) 

0.139 

(0.79) 

Wood studs w/ batt R-13 0.089 

(0.292) 

0.0485 

(0.028) 

73.4 

(4.58) 

0.837 

(0.2) 

1.82 

(10.34) 

Gypsum board 0.0127 

(0.042) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.079 

(0.45) 

12 
St Louis, Miami, Phoenix Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2-K/W

(hr-ft2-F/Btu)

Wood fiber-cement clapboards 

0.0634 

(0.208) 

0.171 

(0.099) 

1922 

(120) 

1.00 

(0.24) 

0.037 

(0.21) 

OSB sheathing 0.0127 

(0.042) 

0.0917 

(0.053) 

288 

(18) 

1.30 

(0.31) 

0.139 

(0.79) 

Wood studs w/ batt R-13 0.089 

(0.292) 

0.0485 

(0.028) 

73.4 

(4.58) 

0.837 

(0.2) 

1.82 

(10.34) 

Gypsum board 0.0127 

(0.042) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.079 

(0.45) 

Roof Construction:

All Locations Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Asphalt shingles 0.0114 

(0.0375) 

1.475 

(0.852) 

1120 

(70) 

1.47 

(0.35) 

0.078 

(0.44) 

Oriented strand board (waferboard) 

sheathing 

0.0128 

(0.042) 

0.0917 

(0.053) 

288 

(18) 

1.298 

(0.31) 

0.14 

(0.79) 

Top Floor Ceiling Construction:

All Locations Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Insulated wood trusses 0.254 

(0.833) 

0.0389 

(0.0225) 

57.5 

(3.59) 

0.837 

(0.2) 

6.52 

(37.04) 

Slab Construction:

All Locations Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2-K/W

(hr-ft2

-F/Btu)

Concrete normal weight 0.127 

(0.4167) 

1.31 

(0.7576) 

2240 

(140) 

0.837 

(0.2) 

0.097 

(0.55) 

Floor Construction:

All Locations Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3

)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Gypcrete 0.0128 

(0.042) 

0.160 

(0.0926) 

800 

(50) 

0.84 

(0.2) 

0.079 

(0.45) 

Plywood 0.0191 

(0.0625) 

0.116 

(0.0669) 

545 

(34) 

1.21 

(0.29) 

0.164 

(0.93) 

Wood Joists w/acoustic batts 0.254 

(0.833) 

0.0673 

(0.0389) 

57.5 

(3.59) 

1.67 

(0.4) 

3.78 

(21.44) 

13 
Ceiling (except top floor) Construction:

All Locations Thickness Conductivity Density Specific Heat Resistance 

Description m 

(ft) 

W/m-K

(Btu/hr-ft-F) 

kg/m3

(lb/ft3)

kJ/kg-K 

(Btu/lb-F) 

m2

-K/W

(hr-ft2

-F/Btu)

Gypsum board 0.0127 

(0.042) 

0.160 

(0.0926) 

800 

(50) 

0.837 

(0.2) 

0.079 

(0.45) 

Window:

U-value SHGC

Location 

W/m2

-K 

(Btu/hr-ft2

-F) 

St. Louis, Bismarck, and Minneapolis

3.80 

(0.67) 0.39 

Miami and Phoenix 7.21 

(1.27) 0.25 

The internal gains for the occupied spaces are calculated based on a total sensible heat gain per day per unit 

to account for a combination of lights, people and equipment per the Space Conditioning calculation 

procedure of Standard 90.2 (ASHRAE 2001d). These gains equal 21,100 kJ (20,000 Btu) plus the floor 

area times 170 kJ/m2

 (15 Btu/ft2) and are scheduled as shown in Figure 10. The total latent heat gains are 

assumed to be 0.2 times the sensible gains. 

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 2 4 6 8 10 12 14 16 18 20 22 24

Hour of day

Multiplier for internal gai

ns

 

Figure 10 Residential building internal gains schedule 

The thermostats operate on a setpoint with setback/setup basis. The heating setpoint is 20.0 °C (68 °F) and 

the cooling setpoint is 25.6 °C (78 °F). The schedule for the setback/setup for the living units is shown in

Figure 11. The lobby and corridor zones are heated to 20.0 °C (68 °F) and cooled to 25.6 °C (78 °F). 

14 
0

5

10

15

20

25

30

0 2 4 6 8 10 12 14 16 18 20 22 24

Hour of day

Temperature (°

C)

Workday_Heat

Workday_Cool

Weekend_Heat

Weekend_Cool

Figure 11 Thermostat schedule for residential building 

15 
Airflow Models 

This section provides the details of the airtightness levels used in the study. Three different airtightness 

levels (No air barrier, target, and best achievable) were modeled in each building by changing the leakage 

characteristics in the CONTAM multizone airflow models for each building. The values for the no air 

barrier level varied for each location, while the target and best achievable construction cases were the same

for all locations. The values for the no air barrier (i.e., baseline) case were established through an analysis

of the available published airtightness data for buildings other than low-rise residential buildings. 

The majority of the data were compiled in a 1998 summary (Persily 1998) supplemented by additional data 

including more Florida commercial buildings, additional U.K. office buildings, and Canadian apartment

buildings added during this study [see references in Appendix A]. The entire dataset of 166 buildings (144 

in North America and 22 in U.K.) and the references are presented in Appendix A. This dataset includes all

data from the ASHRAE Handbook of Fundamentals (ASHRAE 2001c) but adds data from over 150 

additional buildings reported in 13 different studies. Since these data are intended to represent only the 

baseline case, no buildings known to have been constructed to a specific airtightness level are included. 

Most of the air leakage rates in the dataset were determined using ASTM E779 fan pressurization tests 

(ASTM 1999). Others were tested by very similar methods such as Canadian (CGSB 1986 and CGSB

1999), International (ISO 1996) or British (CIBSE 2000) standards. Proskiw and Philips (2001) summarize 

and compare these and other current or proposed building airtightness testing methods. 

As reference points, average airtightness levels from various subsets of the data, in units of L/s-m2

 (cfm/ft2) 

at an indoor-outdoor pressure difference of 75 Pa (0.3 in H2O), normalized by above-grade envelope 

surface area are as follows: 

NIST studies (U.S. office buildings): 4.2 L/s-m2

 (0.83 cfm/ft2) 

Brennan paper (NY schools): 2.4 L/s-m2

 (0.47 cfm/ft2) 

NRCC (Canadian large offices): 2.9 L/s-m2

 (0.57 cfm/ft2) 

NRCC (Canadian schools): 7.9 L/s-m2

 (1.6 cfm/ft2) 

NRCC (Canadian retail buildings): 13.7 L/s-m2

 (2.7 cfm/ft2) 

Mulitple studies (Canadian apartment buildings): 3.1 L/s-m2

 (0.61 cfm/ft2) 

BRE and BSRIA (U.K. office buildings): 7.2 L/s-m2

 (1.4 cfm/ft2) 

FSEC studies (mixed small commercial): 12.6 L/s-m2

 (2.5 cfm/ft2) 

Based on the available information, the dataset was reduced by excluding buildings older than 1960 (even 

though examination of the data by U.S., Canadian and U.K. authors have found no trends toward increased 

airtightness in more recent buildings [Persily 1998, Proskiw and Phillips 2001, and Potter et al. 1995]), all 

industrial buildings, and one extremely leaky building. The data were then divided into north (Standard 

90.1 climate zones 5 and above) and south (Standard 90.1 climate zones 4 and below) subsets for North 

American buildings only. Unfortunately, the available data are inadequate to support a breakdown by the 

individual climate zones. Finally, within those North and South subsets, average airtightness was calculated 

for short buildings (3 stories and less) and tall buildings (4 stories and up) as the data demonstrate that the 

tall buildings are tighter on average. The average airtightness values (again in units of L/s-m2

 at 75 Pa 

(cfm/ft2

 at 0.3 in H2O), normalized by above-grade envelope surface area) are as follows: 

North_short (29 buildings): 6.6 L/s-m2

 (1.3 cfm/ft2) 

South_short (74 buildings): 11.8 L/s-m2

 (2.3 cfm/ft2) 

Based on consideration of the available data, the average measured value from the short buildings in the 

south was used as the baseline value in the warmest climate (Miami) and the average measured value from

the short buildings in the north was used as the baseline value in the coldest climate (Bismarck). The values 

for the remaining locations were assigned by linearly interpolating between these values using the number 

of heating degree days (HDD) for the location. As a result, the whole building air leakage values used were 

(in units of L/s-m2

 at 75 Pa (cfm/ft2 @ 0.3 inH2O) and normalized by above-grade envelope surface area) 

as follows: 

16 
No air barrier: 

Miami 11.8 L/s-m2

 (2.3 cfm/ft2) 

Phoenix 11.1 L/s-m2

 (2.2 cfm/ft2) 

St. Louis 9.1 L/s-m2 (1.8 cfm/ft2) 

Minneapolis 7.2 L/s-m2

 (1.4 cfm/ft2) 

Bismarck 6.6 L/s-m2

 (1.3 cfm/ft2) 

In addition to the baseline level, all buildings were modeled at two levels of increased airtightness. Both

published building airtightness data and current commercial buildings airtightness standards were 

considered in selecting these levels. The ‘target’ level was selected to represent a level of airtightness that 

can be achieved through good construction practice, while the ‘best achievable’ level is based on the 

tightest levels reported for nonresidential buildings. Achieving the tightest level would require an 

aggressive program of quality control during construction and airtightness testing, combined with efforts to

identify and repair any leaks. 

Target: 1.2 L/s-m2

 (0.24 cfm/ft2) 

Best achievable: 0.2 L/s-m2 (0.04 cfm/ft2)

About 6 % of the tested buildings listed in Appendix A would meet the 1.2 L/s-m2

 (0.24 cfm/ft2) selected 

target airtightness level. Note that none of these tested buildings was built to an airtightness standard. For 

comparison, the average reported airtightness level was calculated for non-residential buildings in the U.K., 

Ireland, and Germany that were constructed to specified whole building airtightness targets as reported in

Building Services Journal articles and elsewhere (Anon. 1998, Anon. 2002, Anon. 2003, Cohen 2003, 

Olivier 2001and Kennett 2004). These 14 buildings, which were of various envelope construction types 

(curtain wall, masonry, frame, and mixed) and ranged from 1 story to 6 stories, averaged 1.3 L/s-m2

 at 

75 Pa (0.25 cfm/ft2

 at 0.3 inH2O). 

In addition to simulations at these levels, the ‘no air barrier’ and target levels were varied as part of a 

sensitivity analyses, as described below. 

Although the whole building air leakage dataset in Appendix A lacks data for U.S. apartment buildings, a 

literature review by Edwards (1999) reported air leakage for apartment units in 16 U.S. buildings from four 

studies (Modera et al. 1985, Diamond et al. 1986, Synertech 1987, Feustel and Diamond 1996). The 

average leakage of these 16 buildings was 20 cm2

 per m2 (0.29 in2 per ft2) of floor area at 4 Pa. For the 

apartment building modeled in this study (and assuming uniform distribution over all apartment surfaces), 

this value corresponds to 11.6 L/s-m2

 at 75 Pa (2.3 cfm/ft2 at 0.3 in H2O), which is leakier than the average 

value used in the models discussed above. Also, no direct leakage between adjacent units was assumed for 

the apartment building. Suite access doors from the hallways were modeled as an effective leakage area of 

200 cm2

 (31 in2) at 4 Pa based on measurements by Wray et al. (1998). 

17 
System Models 

The HVAC systems modeled were specified to be representative of systems that would be installed in 

typical practice. The systems were different for the different building types and were sized for the 

appropriate locations. Whether each system included an economizer for the different locations was based 

on the criteria in ASHRAE 90.1. 

Office Building:

The office building system included water-source heat pumps (WSHPs) with a cooling tower and a boiler 

serving the common loop. Each zone had its own WSHP rejecting/extracting heat from the common loop. 

The outdoor air for each zone was supplied to each individual heat pump, and the heat pump blower was on 

at all times when the zone was occupied. When the location of the building required an economizer, the 

outdoor air controls were applied to the individual heat pump’s airflow. With this approach, different heat

pumps could have a different percentage of outdoor air at the same time depending on the loads. For the 

five modeled locations, St. Louis, Bismarck and Phoenix included economizers and Minneapolis and 

Miami did not. Return airflow was specified to equal 95 % of supply airflow. 

Retail Building:

The retail building system was a packaged rooftop unit including a DX cooling coil and a gas furnace, with 

a separate system for each individual zone. The required outdoor air was provided by each individual unit 

so the blower was on at all times when the zone was occupied. When the location of the building required 

an economizer the outdoor air controls were applied to the individual unit’s airflow. In this manner 

different units could have a different percentage of outdoor air at the same time depending on the loads. For 

the selected locations, St. Louis, Bismarck and Phoenix included economizers and Minneapolis and Miami

did not. Return airflow was specified to equal 95 % of supply airflow. 

Residential Building:

The systems are modeled using manufacturer's data for a residential DX coil with gas furnace, with a 

separate system for each individual zone. No outdoor air is provided by the system, and therefore no 

economizer system is modeled. For the gas furnace a simple unit efficiency is used to calculate the required 

gas input and the heat output for each timestep that requires heating. (This is around 80 % for all the units.) 

For cooling, the manufacturer’s data has corrections for the coil performance and energy consumption 

based on air conditions at the condenser and evaporator coils. These were single speed units that operate on 

a on/off basis rather than a reduced speed basis. The simulation uses 5 min timesteps so the minimum time 

that a unit is on is 5 min. (These units range from 12.0 to 13.25 SEER at ARI 210 rating conditions.) Also, 

exhaust ventilation will be modeled for each unit with the following values and schedules: 

Bathroom exhaust: 23.6 L/s (50 cfm) from 7:00 a.m. to 7:30 a.m. daily

Kitchen exhaust: 47.2 L/s (100 cfm) from 6:00 p.m. to 7:00 p.m. daily

Dryer exhaust: 118 L/s (250 cfm) from 1:00 p.m. to 4:00 p.m. on Saturday only

18 
Scalar Calculation 

ASHRAE Standing Standard Project Committee 90.1 has historically selected, and then implemented, 

energy conservation measures for inclusion in the standard on the basis of a reasonable return on 

investment in terms of energy saved vs. first cost using life cycle cost economic analysis. In order to apply

uniform rules across the different requirements of the standard, whether they are insulation levels or 

lighting efficiency, a uniform rule is applied to all measures according to whole building energy analysis of 

prototypical buildings. This rule is based on a multiplier for the energy saved that includes mulitple 

economic factors, such as the number of years, the cost of money and interest rates. The dimensionless 

multiplier is termed a Scalar Ratio by the 90.1 committee. At the time of update of the standard from

ASHRAE 90.1-1989 to ANSI/ASHRAE/IESNA Standard 90.1- 1999, the development of the scalar ratio

and its application across disciplines was documented in McBride (1995) and the value used in this update

process was “8”. 

This life cycle cost methodology was employed in this study to assess the impact of an air barrier 

requirement as simulated. Specifically, the Scalar Ratio pass-fail methodology used when considering 

requirements for potential inclusion in ANSI/ASHRAE/IESNA 90.1 was employed, i.e., the value must be 

less than or equal to a scalar of 8 based on the following equation:

(FYSh*Ph + FYSc*Pc) *8 => ∆FC 

where: FYSh = First year savings in heating (therms) 

Ph = Cost of heating energy ($ per therm)

FYSc = First year savings in cooling (KWh) 

Pc = Cost of cooling energy ($ per KWh) 

∆FC = Cost premium for the energy conservation measure ($) 

The actual scalar for each city was then calculated as: 

∆FC / (FYSh*Ph + FYSc*Pc) = Sac 

where: Sac = Actual scalar 

 

The values used for the cost premium ∆FC were estimated as described below, and were employed to allow 

application of the methodology for the purposes of this study. They are not intended to represent absolute

or standardized cost values; the cost values, like the pass-fail scalar ratio, used by SSPC 90.1 are ultimately 

a committee decision. 

Cost of Energy 

The development of the Standard 90.1 envelope criteria is predicated on the use of national average prices 

for the heating and cooling energies. The fundamental issue is that the buildings covered by the standard 

consist of high-rise residential, commercial and warehouses. Furthermore, each building type can have 

different energy rate schedules, use different energy sources and have a different type of HVAC equipment 

or system. The solution to this problem used by the 90.1 committee has been the development of blended 

heating and cooling energy prices. National averages for electricity and gas were calculated from 2005 

Energy Information Agency data for natural gas, electricity and fuel oil for both residential and commercial

customers. The national average prices are then weighted by the level of construction activity, energy

intensities and end uses, and current efficiencies for the HVAC equipment and forced air distribution 

systems. The energy price for heating consisted of a blending of 75 % natural gas, 14 % fuel oil and 11 % 

electricity. The final blended heating price was $1.01 per therm. The cooling energies investigated were 

electricity (98.3 %) and natural gas (1.7 %) but a decision was made to use just the electricity cost. The 

final blended cooling price was $0.0827 per kWh of electricity. 

Cost Estimate of the Continuous Air Barrier

There are many possible materials and technologies currently available to construct a building envelope 

that will meet the whole building target discussed above. The proposal being considered by the 90.1 

19 
committee would allow buildings to meet the air barrier requirement through any of three paths: 1) a 

material airtightness specification, 2) an assembly airtightness specification, or 3) a whole building 

airtightness specification. The cost estimates were based on selected options to meet the proposed material

airtightness level (0.02 L/s.m2 at 75 Pa [0.004 cfm/ft2 at 0.3 inH2O]) that is judged to be consistent with the 

whole building target used in the energy modeling. 

A cost estimate for both the frame building (option 1 below) and the masonry building was obtained using 

average labor rates from an experienced contractor (TWC 2004) licensed by the Air Barrier Association of 

America (ABAA). A second estimate was obtained from an independent estimator (HFG 2004). The two 

estimates were then reconciled to determine the value used in this analysis. A contractor licensed by a 

national manufacturer of a housewrap product made a third estimate for the frame building (option 2 below, 

Spinu 2004). Sealing the wall air barrier to the windows, foundation and roof or ceiling air barrier was 

excluded from the estimate since they are required under 90.1 presently. It was assumed that these existing 

requirements would be met and the manufacturers’ instructions followed. 

The three tightening approaches considered for the air barrier, and used in the cost estimates presented in 

Table 5, are: 

1. Masonry Back-up Wall Building:

Standard practice in the industry is to use a damp-proofing material on the concrete block in the 

cavity behind the brickwork. Asphaltic damp-proofing can dry and crack over time due to

shrinkage after evaporation of the volatile solvents. Continuous air barrier requirements for 

durability can be achieved using a polymer-modified bituminous elastomeric liquid-applied air 

barrier product, tested to the maximum air leakage requirements of the proposed material

(0.02 L/s.m2

 at 75 Pa [0.004 cfm/ft2 at 0.3 inH2O]). The cost difference between the two materials 

is included in Table 4. 

2. Frame building: 

(Option 1). Since typical housewrap does not meet the requirements for maximum air leakage of 

air barrier materials in the proposed change to the 90.1 standard and gypsum sheathing does 

(Bombaru et al. 1988), the cost of taping the sheathing joints with a durable tape was estimated for 

each building. 

(Option 2). This option is an upgrade from residential quality housewrap material to a commercial 

grade wrap that would meet the proposed air barrier material requirements. An upgrade cost

(Spinu 2004) of $0.028/ft2 multiplied by the gross exterior wall area was used, with a 10 % waste 

and overlap factor added. 

The final cost estimates used for analyzing the target cases in the study are summarized in Table 5. As 

discussed above there are other options that may be used to meet the proposed new criteria for the 90.1 

standard. 

In order to achieve the target air barrier air leakage rate, normal attention to design, construction and 

enforcement is expected to become standard practice after a period of education. However, for the best

achievable case used in the study, additional expenditure would have to be included for quality assurance 

and quality control (i.e., for inspections and testing) as shown in Table 4.

Table 4 Estimated Air Barrier Costs (in dollars) 

Target Case–

Masonry 

Target Case – 

Frame (Option 1) 

Target Case– 

Frame (Option 2) 

Additional QA/QC for 

Best Achievable Case 

Office 12054 4612 325 5795

Retail 7287 2604 176 4745

Apartment NA 5317 370 8153

20 
Results 

The annual gas use, electrical use and average infiltration predicted for the office building is presented in 

Table 5. The annual average infiltration rate with the baseline air leakage ranges from 0.17 h-1 to 0.26 h-1

depending on the climate. Reducing the air leakage rate to the target level results in annual average 

infiltration rates ranging from 0.02 h-1 to 0.05 h-1 for an average reduction in infiltration of 83 %. Further 

tightening of the building envelope to the best achievable level essentially eliminates infiltration for the 

office building. There were no differences in average infiltration between the frame and masonry buildings, 

and only small differences between the masonry and frame buildings for gas and electricity use for heating 

and cooling. Table 6 summarizes the annual energy cost savings for the office building at the target air 

leakage level relative to the baseline level. The annual cost savings are largest in the heating dominated 

climates with potential gas savings of greater than 40 % and electrical savings of greater than 25 %. 

21 
Table 5 Annual gas use, electrical use and annual average infiltration for office building 

Office

SI Units

Bismarck Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 4.6E+08 2.7E+08 2.3E+08 4.6E+08 2.7E+08 2.3E+08

Annual Electricity (kJ) 2.2E+08 1.7E+08 1.4E+08 2.2E+08 1.6E+08 1.4E+08

Annual Average Infiltration (h-1) 0.22 0.05 0.01 0.22 0.05 0.01

Minneapolis Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 4.5E+08 2.5E+08 2.1E+08 4.5E+08 2.5E+08 2.0E+08

Annual Electricity (kJ) 2.4E+08 1.6E+08 1.5E+08 2.4E+08 1.6E+08 1.4E+08

Annual Average Infiltration (h-1) 0.23 0.05 0.01 0.23 0.05 0.01

St. Louis Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 2.7E+08 1.1E+08 8.7E+07 2.7E+08 1.2E+08 8.9E+07

Annual Electricity (kJ) 2.4E+08 1.7E+08 1.7E+08 2.4E+08 1.7E+08 1.7E+08

Annual Average Infiltration (h-1) 0.26 0.04 0.01 0.26 0.04 0.01

Phoenix Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 1.7E+07 3.8E+06 2.8E+06 2.3E+07 8.2E+06 6.2E+06

Annual Electricity (kJ) 2.9E+08 2.6E+08 2.6E+08 2.9E+08 2.6E+08 2.6E+08

Annual Average Infiltration (h-1) 0.17 0.02 0.00 0.17 0.02 0.00

Miami Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 3.2E+05 3.3E+05 3.3E+05 3.2E+05 3.3E+05 3.3E+05

Annual Electricity (kJ) 3.5E+08 3.2E+08 3.2E+08 3.5E+08 3.2E+08 3.2E+08

Annual Average Infiltration (h-1) 0.26 0.03 0.00 0.26 0.03 0.00

IP Units

Bismarck Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 4.4E+08 2.6E+08 2.2E+08 4.4E+08 2.5E+08 2.1E+08

Annual Electricity (Btu) 2.1E+08 1.6E+08 1.3E+08 2.1E+08 1.6E+08 1.3E+08

Annual Average Infiltration (h-1) 0.22 0.05 0.01 0.22 0.05 0.01

Minneapolis Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 4.3E+08 2.4E+08 2.0E+08 4.2E+08 2.4E+08 1.9E+08

Annual Electricity (Btu) 2.3E+08 1.5E+08 1.4E+08 2.3E+08 1.5E+08 1.4E+08

Annual Average Infiltration (h-1) 0.23 0.05 0.01 0.23 0.05 0.01

St. Louis Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 2.5E+08 1.1E+08 8.3E+07 2.5E+08 1.1E+08 8.4E+07

Annual Electricity (Btu) 2.3E+08 1.7E+08 1.6E+08 2.3E+08 1.6E+08 1.6E+08

Annual Average Infiltration (h-1) 0.26 0.04 0.01 0.26 0.04 0.01

Phoenix Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 1.6E+07 3.6E+06 2.7E+06 2.2E+07 7.8E+06 5.9E+06

Annual Electricity (Btu) 2.7E+08 2.5E+08 2.5E+08 2.8E+08 2.5E+08 2.5E+08

Annual Average Infiltration (h-1) 0.17 0.02 0.00 0.17 0.02 0.00

Miami Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 3.1E+05 3.1E+05 3.1E+05 3.1E+05 3.1E+05 3.1E+05

Annual Electricity (Btu) 3.3E+08 3.0E+08 3.0E+08 3.3E+08 3.0E+08 3.0E+08

Annual Average Infiltration (h-1) 0.26 0.03 0.00 0.26 0.03 0.00

22 
Table 6 Energy cost savings for office building 

Retail building

Table 7 presents the annual gas use, electrical use and average infiltration predicted for the retail building. 

The annual average infiltration for the retail building with the baseline air leakage ranges from 0.13 h-1 to

0.24 h-1. Reducing the air leakage rate to the target level almost eliminates infiltration, with all climates 

having an average rate of less than 0.02 h-1. Further tightening of the building envelope to the best

achievable level completely eliminates infiltration for the retail building. Again, there were very few 

differences between the frame and masonry buildings in either average infiltration or energy. Table 8

summarizes the annual energy cost savings for the retail building at the target air leakage level relative to

the baseline level. Unlike the office building, the predicted cost savings for the retail building are fairly 

independent of climate. The electrical savings in the hot climates are about as large as the gas savings in the 

cold climates in absolute terms. 

City

Total 

Savings

Bismarck $1,854 42% $1,340 26% $3,195

Minneapolis $1,872 43% $1,811 33% $3,683

St. Louis $1,460 57% $1,555 28% $3,016

Phoenix $124 77% $620 9% $745

Miami $0 0% $769 10% $769

Electrical

 Savings

Gas

Savings

23 
24 

Table 7 Annual gas use, electrical use and annual average infiltration for retail building 

Retail

SI Units

Bismarck Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 7.4E+08 5.5E+08 5.3E+08 7.4E+08 5.5E+08 5.3E+08

Annual Electricity (kJ) 7.9E+07 7.7E+07 7.8E+07 7.8E+07 7.7E+07 7.7E+07

Annual Average Infiltration (h-1) 0.20 0.02 0.00 0.20 0.02 0.00

Minneapolis Frame Building Masonry Building

Baseline Target Best Baseline Target Best

st

E+08

8

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 2.9E+07 1.0E+07 1.0E+07 3.2E+07 1.3E+07 1.3E+07

Annual Electricity (kJ) 3.1E+08 2.6E+08 2.6E+08 3.1E+08 2.7E+08 2.7E+08

Annual Average Infiltration (h-1) 0.13 0.00 0.00 0.13 0.00 0.00

Miami Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 7.0E+05 1.6E+04 1.6E+04 5.0E+05 0.0E+00 0.0E+00

Annual Electricity (kJ) 3.7E+08 3.2E+08 3.2E+08 3.7E+08 3.2E+08 3.2E+08

Annual Average Infiltration (h-1) 0.21 0.01 0.00 0.21 0.01 0.00

IP Units

Bismarck Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 7.0E+08 5.2E+08 5.0E+08 7.0E+08 5.2E+08 5.0E+08

Annual Electricity (Btu) 7.5E+07 7.3E+07 7.4E+07 7.4E+07 7.3E+07 7.3E+07

Annual Average Infiltration (h-1) 0.20 0.02 0.00 0.20 0.02 0.00

Minneapolis Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 6.7E+08 4.8E+08 4.6E+08 6.7E+08 4.8E+08 4.6E+08

Annual Electricity (Btu) 8.2E+07 6.7E+07 6.3E+07 8.1E+07 6.6E+07 6.2E+07

Annual Average Infiltration (h-1) 0.22 0.02 0.00 0.22 0.02 0.00

St. Louis Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 3.8E+08 2.3E+08 2.2E+08 3.8E+08 2.4E+08 2.3E+08

Annual Electricity (Btu) 1.4E+08 1.3E+08 1.3E+08 1.4E+08 1.3E+08 1.3E+08

Annual Average Infiltration (h-1) 0.24 0.01 0.00 0.24 0.01 0.00

Phoenix Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 2.7E+07 9.9E+06 9.8E+06 3.0E+07 1.2E+07 1.2E+07

Annual Electricity (Btu) 2.9E+08 2.5E+08 2.5E+08 2.9E+08 2.5E+08 2.5E+08

Annual Average Infiltration (h-1) 0.13 0.00 0.00 0.13 0.00 0.00

Miami Frame Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 6.6E+05 1.5E+04 1.5E+04 4.8E+05 0.0E+00 0.0E+00

Annual Electricity (Btu) 3.5E+08 3.0E+08 3.0E+08 3.5E+08 3.0E+08 3.0E+08

Annual Average Infiltration (h-1) 0.21 0.01 0.00 0.21 0.01 0.00

Annual Gas (kJ) 7.1E+08 5.1E+08 4.9E+08 7.1E+08 5.1E+08 4.9E+08

Annual Electricity (kJ) 8.6E+07 7.0E+07 6.7E+07 8.6E+07 7.0E+07 6.6E+07

Annual Average Infiltration (h-1) 0.22 0.02 0.00 0.22 0.02 0.00

St. Louis Frame Building Masonry Building

Baseline Target Best Baseline Target Be

Annual Gas (kJ) 4.0E+08 2.5E+08 2.4E+08 4.0E+08 2.5E+08 2.4

Annual Electricity (kJ) 1.5E+08 1.4E+08 1.4E+08 1.5E+08 1.4E+08 1.4E+0

Annual Average Infiltration (h-1) 0.24 0.01 0.00 0.24 0.01 0.00

Phoenix Frame Building Masonry Building
Table 8 Energy cost savings for retail building 

Residential building

Table 9 presents the annual gas use, electrical use and average infiltration predicted for the apartment 

building. The annual average infiltration rate for the apartment building with the baseline air leakage ranges 

is slightly higher than the other buildings and ranges from 0.19 h-1 to 0.26 h-1. Reducing the air leakage to 

the target level results in an average reduction in infiltration of 64 %. Further tightening of the building

envelope to the best achievable level further reduces the infiltration by an average of 33 %. The infiltration

remains higher in the tighter apartment buildings relative to the other buildings due to the lack of a 

mechanical system pressurization effect. The clapboard siding and masonry veneer buildings were quite

similar with the masonry building resulting in slightly lower gas use. 

Table 10 summarizes the annual energy cost savings for the apartment building at the target air leakage 

level relative to the baseline level. Similar to the office building, the predicted cost savings for the 

apartment building are largest in the cold climates with gas savings of 40 % or more.

City

Total 

Savings

Bismarck $1,835 26% $33 2% $1,869

Minneapolis $1,908 28% $364 18% $2,272

St. Louis $1,450 38% $298 9% $1,748

Phoenix $176 64% $992 14% $1,169

Miami $6 98% $1,224 14% $1,231

Gas Savings

Electrical 

Savings

25 
Table 9 Annual gas use, electrical use and annual average infiltration for apartment building 

Apartment

SI Units

Bismarck Clapboard Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 5.7E+08 3.5E+08 2.9E+08 5.6E+08 3.4E+08 2.8E+08

Annual Electricity (kJ) 5.7E+07 6.2E+07 6.6E+07 5.7E+07 6.2E+07 6.6E+07

Annual Average Infiltration (h-1) 0.22 0.09 0.06 0.22 0.09 0.06

Minneapolis Clapboard Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 5.7E+08 3.2E+08 2.8E+08 5.6E+08 3.2E+08 2.6E+08

Annual Electricity (kJ) 5.3E+07 6.0E+07 6.2E+07 5.3E+07 6.0E+07 6.2E+07

Annual Average Infiltration (h-1) 0.24 0.09 0.06 0.24 0.09 0.06

St. Louis Clapboard Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 3.3E+08 1.4E+08 1.2E+08 3.2E+08 1.4E+08 1.2E+08

Annual Electricity (kJ) 8.7E+07 9.7E+07 1.0E+08 8.7E+07 9.7E+07 1.0E+08

Annual Average Infiltration (h-1) 0.25 0.09 0.06 0.26 0.09 0.06

Phoenix Clapboard Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 2.2E+07 8.1E+06 8.4E+06 2.0E+07 6.6E+06 7.3E+06

Annual Electricity (kJ) 1.9E+08 1.8E+08 1.9E+08 1.8E+08 1.8E+08 1.9E+08

Annual Average Infiltration (h-1) 0.19 0.07 0.05 0.19 0.07 0.05

Miami Clapboard Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (kJ) 5.3E+06 2.1E+06 2.0E+06 4.8E+06 1.7E+06 1.7E+06

Annual Electricity (kJ) 1.9E+08 1.8E+08 1.7E+08 1.9E+08 1.8E+08 1.7E+08

Annual Average Infiltration (h-1) 0.26 0.08 0.05 0.26 0.08 0.05

IP Units

Bismarck Clapboard Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 5.4E+08 3.3E+08 2.7E+08 5.3E+08 3.2E+08 2.7E+08

Annual Electricity (Btu) 5.4E+07 5.9E+07 6.2E+07 5.4E+07 5.9E+07 6.2E+07

Annual Average Infiltration (h-1) 0.22 0.09 0.06 0.22 0.09 0.06

Minneapolis Clapboard Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 5.4E+08 3.0E+08 2.6E+08 5.3E+08 3.1E+08 2.4E+08

Annual Electricity (Btu) 5.0E+07 5.7E+07 5.9E+07 5.0E+07 5.7E+07 5.9E+07

Annual Average Infiltration (h-1) 0.24 0.09 0.06 0.24 0.09 0.06

St. Louis Clapboard Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 3.1E+08 1.4E+08 1.2E+08 3.1E+08 1.3E+08 1.1E+08

Annual Electricity (Btu) 8.3E+07 9.2E+07 9.5E+07 8.2E+07 9.2E+07 9.5E+07

Annual Average Infiltration (h-1) 0.25 0.09 0.06 0.26 0.09 0.06

Phoenix Clapboard Building Masonry Building

Baseline Target Best Baseline Target Best

Annual Gas (Btu) 2.1E+07 7.6E+06 8.0E+06 1.9E+07 6.2E+06 6.9E+06

Annual Electricity (Btu) 1.8E+08 1.8E+08 1.8E+08 1.7E+08 1.7E+08 1.8E+08

Annual Average Infiltration (h-1) 0.19 0.07 0.05 0.19 0.07 0.05

Miami Clapboard Building Masonry Building

Baseline Target Best Baseline Target Best

nnual Gas (Btu) 5.0E+06 1.9E+06 1.9E+06 4.6E+06 1.6E+06 1.6E+06

nnual Electricity (Btu) 1.8E+08 1.7E+08 1.6E+08 1.8E+08 1.7E+08 1.6E+08

nnual Average Infiltration (h-1) 0.26 0.08 0.05 0.26 0.08 0.05

A

A

A

26 
apartment building cooling setpoints 

urs

al

cooling

would open windows for the free cooling. Figure 12 demonstrates this effect for the apartment building in

Phoenix. The tighter target air leakage level results in predicted increases in cooling energy use from

October through April but reduces cooling energy in the hottest months of June through September. The 

average savings during these hot months is 10 %. 

 

Table 10 Energy cost savings for apartment building 

Unlike the retail and o

City

Total 

Savings

Bismarck $2,187 40% -$116 -9% $2,071

Minneapolis $2,421 43% -$165 -14% $2,256

St. Louis $1,794 57% -$232 -12% $1,562

$133

$411

Gas 

Savin

Phoenix $133 65% $0 0%

Miami $31 63% $380 9%

gs

Electrical 

Savings

ffice buildings, tightening the residential building envelope in the cooler climates 

resulted in a predicted electrical cost penalty of up to 14 %. In all of the building types, there are some

hours where the reduction of infiltration eliminates a ‘free cooling’ effect during which time the cool 

outdoor air offsets the internal heat gain of the building. However, in the apartment building for these 

cooler climates, this impact summed over the course of the year more than offsets the impact of lower 

infiltration during hot hours when it adds to the cooling load. There are key differences between the 

building types that produce this effect. First, the apartment building lacks both an economizer to

purposefully take advantage of free cooling effect. In fact, the apartment also lacks continuous ventilation

to coincidentally take advantage of the free cooling effect. Second, the

are higher during the day and lower at night, which results in smaller cooling loads during the hottest ho

and larger cooling hours during the cooler hours. However, it is likely that some of the predicted electric

use for cooling in the residential building would not occur in the real world because part of the free

effect happens during winter or shoulder seasons when residents may not operate their air-conditioning and 

27 
0.0E+00

5.0E+06

1.0E+07

1.5E+07

2.0E+07

2.5E+07

3.0E+07

3.5E+07

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Monthly electrical use (kJ)

Baseline

Target

28 

Figure 12 Monthly electrical use in Phoenix apartment building 

Comparison to CBECS-derived benchmarks 

Since these prototype buildings are not based on an actual building, it is not possible to directly validate the 

model predictions. However, it is valuable to compare the predictions to available benchmarks of heating 

and cooling energy use in comparable U.S. buildings. One option is to compare the predicted annual gas 

and electricity use to recent Commercial Building Energy Consumption Survey (CBECS) results available 

from the U.S. Department of Energy. The most recent available commercial energy data available are for 

1999 (http://www.eia.doe.gov/emeu/cbecs/detailed_tables_1999.html). The CBECS does not directly

measure the portion of energy used in buildings for heating and cooling, but instead uses statistical methods 

to derive estimates of energy end-use consumption. 

For the 1999 CBECS, a new nonlinear regression method was used to estimate the total energy used, with a 

breakdown by principal building activity. To compare the results from this study, the results for the three 

baseline buildings were normalized by floorspace area. Similarly, the aggregate energy end-use data for the 

Office and Retail (Other than Mall) categories were normalized by the closest available floorspace numbers 

from the 1999 CBECS Building Characteristics tables. The 1999 CBECS value for natural gas used for 

space heating was normalized by total floorspace area in buildings with gas heating, the value for electricity 

used for cooling was normalized by total floorspace with cooling, and the value for ventilation was 

normalized by the total floorspace. CBECS also includes a small amount of electricity used for space 

heating but this amount was neglected. The normalized values of electricity used for cooling and electricity

were then added to obtain the total electricity used for space conditioning. 

The values derived from the 1999 CBECS data are presented in Table 11. Note that these values vary

considerably from the Commercial Buildings Energy End-Use Intensities listed in the 2004 Buildings 

Energy Databook (DOE 2004). One cause of the difference is that the Buildings Energy Databook uses 

older CBECS data from 1995. More significantly, the 1995 CBECS data is based on the discontinued 

methodology. As explained on the DOE Energy Information Agency website
(http://www.eia.doe.gov/emeu/cbecs/enduse_consumption/compare.html), applying the new methodology

to the 1995 data results in significant changes, presumably improvements, to the energy end-use estimates. 

Similarly, normalized national averages for space heating gas and air-conditioning electricity usage in the 

apartment buildings were calculated from the 2001 U.S. Department of Energy Residential Energy

Consumption Survey (RECS) data (http://www.eia.doe.gov/emeu/recs/contents.html). The housing 

category used was Apartments in Buildings with 5 or More Units and energy usage was based on Units

with Natural Gas as the Main Space Heating Fuel for gas and on Units with Central Air-Conditioning for 

electricity. 

Since the CBECS and RECS estimates represent national averages, they are compared to the average of the 

predicted results for the five locations. While the averaged results from this study should not be interpreted 

as representing a true national average, the goal of this comparison is not a comprehensive validation but

rather to establish the reasonableness of the baseline cases. As seen in Table 11, the average predictions for 

the baseline cases are all at least 20 % below the values calculated from the 1999 CBECS-derived and 2001 

RECS-derived national average data except for the gas used by the retail prototype, which is less than 10 % 

higher. Considering that the CBECS estimates include buildings of all ages, sizes, construction types, etc., 

there are many factors that could explain such differences. However since model input decisions were 

made with the intent of making a conservative prediction, it is not surprising that the predicted values are 

mostly lower than the CBECS derived values. This indicates that the calculated savings in absolute terms 

would be even larger than presented above thus resulting in lower scalar values than estimated. While the 

apartment baseline results are significantly different than the RECS average, the simulation results are 

similarly lower thus ensuring that the calculated energy savings are not due to reductions in unrealistically

large baseline loads. 

Table 11 Comparisons of Predicted Gas and Electricity Used to CBECS and RECS Estimates

 Baseline Office 

Prototype 

Baseline Retail Prototype Baseline Apartment 

Prototype 

Location

Gas 

MJ/m2

(kBtu/ft2

) 

Electricity 

kW·h/m2

 (kBtu/ft2

) 

 Gas 

MJ/m2

(kBtu/ft2

) 

Electricity 

kW·h/m2

 (kBtu/ft2

) 

 Gas 

MJ/m2

(kBtu/ft2

) 

Electricity 

kW·h/m2

 (kBtu/ft2

) 

Bismarck 200 (18) 28 (9.0) 660 (58) 19 (6.2) 171 (15) 4.7 (1.5) 

Minneapolis 200 (18) 30 (9.4) 630 (55) 21 (6.7) 171 (15) 4.4 (1.4) 

St. Louis 110 (10) 30 (9.6) 350 (31) 38 (12) 98 (8.6) 6.9 (2.2) 

Phoenix 8.0 (0.7) 35 (11) 26 (2.3) 76 (24) 6.8 (0.6) 15 (4.8) 

Miami 0 44 (14) 1.1 (0.1) 91 (29) 1.1 (0.1) 15 (4.9) 

Average 110 (9.4) 35 (11) 330 (29) 50 (16) 88 (7.7) 9.4 (3.0) 

 

1999 

CBECS 388 (34) 82 (26) 310 (27) 63 (20) NA NA 

2001 RECS NA NA NA NA 285 (25) 22 (6.9) 

In addition to the CBECS values, the office building simulation results were also compared to predictions

from a Pacific Northwest Laboratories study (Crawley and Schliesing 1992). In this study the DOE-2 

building energy simulation tool was used to predict the annual energy consumption for a two-story office 

building in Greensboro, NC, Tucson, AZ, and Scranton, PA. They found heating gas use of 207 MJ/m2

(18.2 kBtu/ft

2

) and cooling and fan electricity use of 67.1 kW·h/m2 (21.3 kBtu/ft

2

) for Greensboro, heating 

energy use of 52.2 MJ/m2

 (4.6 kBtu/ft2) and cooling and fan electricity use of 99.2 kW·h /m2 (31.5 kBtu/ft

2

) 

for Tucson, and heating gas use of 260 MJ/m2

 (22.9 kBtu/ft

2

) and cooling and fan electricity use of 

35.3 kW·h /m2

 (11.2 kBtu/ft

2

) for Scranton. While there are many differences between the PNL buildings 

nd the assumptions in this study, the gas and electricity use for the baseline office buildings in Table 12 

r the closest comparable climates are all conservative compared to the PNL study. 

a

fo

29 
Cost Effectiveness 

As described earlier, a cost effectiveness analysis of the air barrier energy savings was conducted using the 

scalar ratio methodology employed by SSPC 90.1. This cost analysis was performed to put the calculated 

energy savings in context using estimated values of the costs associated with the air barrier measures. As 

seen in Table 12, the majority of cases with one exception (the office building with masonry backup in

climate zones 1 and 2) have a Scalar Ratio less than 8 for the Target case. Based on this criterion, the 

residential building can use either of the airtightening options outlined in climate zones 3 and higher, but

Option 2 is more cost effective in climate zones 1 and 2. 

e continuous air barrier is cost-effective in climate 

1 and 2, although significant, is not enough to

air 

Office building: The masonry building expenditure on th

zoned 3 and higher. The energy savings in climate zones

offset the expenditure for the air barrier within the accepted guidelines of 90.1; in other words, with a 

Scalar of 16.2 or higher, it does not meet the maximum Scalar Ratio limit of 8. This would imply that an

exception for masonry buildings in climate zones 1 and 2 is suggested by the study. The frame building

barrier is cost effective with both airtightening strategies in all climates. 

Retail building: The Scalar Ratio calculated for all the climate zones for both the masonry and frame

building types indicate that all air barrier strategies are cost-effective. 

Multi-Unit Apartment Building: Based on the Scalar Ratio, the air barrier strategy option 1 is not costeffective in climate zones 1 and 2, but the air barrier strategy option 2 is cost-effective in all climates. 

There is no significant difference between the building with clapboard siding and masonry veneer. 

30 
31 

Table 12 Summary of Calculated Scalar Ratios 

Two Story Office Building Bismarck MinneapolisSt. Louis Phoenix Miami

Cost of energy saved x Scalar of 8 $25,701 $25,701 $24,122 $5,956 $6,153

Masonry Backup Wall

First cost of the air barrier $12,054 $12,054 $12,054 $12,054 $12,054

Calculated Scalar 3.8 3.8 4.0 16.2 15.7

Steel Frame Building - Taped sheathing (Option 1)

First cost of the air barrier $4,612 $4,612 $4,612 $4,612 $4,612

Calculated Scalar 1.4 1.4 1.5 6.2 6.0

Steel Frame Building - Commercial Wrap (Option 2)

First cost of the air barrier $325 $325 $325 $325 $325

Calculated Scalar 0.1 0.1 0.1 0.4 0.4

One Story Retail Building Bismarck MinneapolisSt. Louis Phoenix Miami

Cost of energy saved x Scalar of 8 $14,946 $18,174 $13,985 $9,345 $9,840

Masonry Backup Wall

First cost of the air barrier $7,287 $7,287 $7,287 $7,287 $7,287

Calculated Scalar 3.9 3.2 4.2 6.2 5.9

Steel Frame Building - Taped sheathing (Option 1)

First cost of the air barrier $2,604 $2,604 $2,604 $2,604 $2,604

Calculated Scalar 1.4 1.1 1.5 2.2 2.1

Steel Frame Building - Commercial Wrap (Option 2)

First cost of the air barrier $176 $176 $176 $176 $176

Calculated Scalar 0.1 0.1 0.1 0.2 0.1

Four Story Wood Frame Apartment Building (Clapboard Siding) Bismarck MinneapolisSt. Louis Phoenix Miami

$18,045 $12,498 $1,067 $3,294

$5,317 $5,317 $5,317 $5,317 $5,317

0

Co

Ta

st of energy saved x Scalar of 8 $16,567

ped sheathing (Option 1)

First cost of the air barrier 

Calculated Scalar 2.6 2.4 3.4 39.9 12.9

Commercial Wrap (Option 2)

First cost of the air barrier $370 $370 $370 $370 $37

Calculated Scalar 0.2 0.2 0.2 2.8 0.9

Four Story Wood Frame Apartment Building (Masonry Veneer) Bismarck MinneapolisSt. Louis Phoenix Miami

Cost of energy saved x Scalar of 8 $16,468 $17,067 $12,326 $994 $

Taped sheathing (Option 1)

First cost of the air barrier 

Calculated Scalar

3,286

$5,317 $5,317 $5,317 $5,317 $5,317

2.6 2.5 3.5 42.8 12.9

Commercial Wrap (Option 2)

First cost of the air barrier $370 $370 $370 $370 $370

Calculated Scalar 0.2 0.2 0.2 3.0 0.9

Color key:

3.8 Scalar = < 8

16.2 Scalar > 8
Sensitivity Analysis 

Although the energy and airflow models used for this study require many input values, two of the most

important values in determining the potential cost effectiveness of the proposed air barrier requirements are 

lues 

ilding

fm/ft2 at 0.3 in H2O). Scalar ratios were calculated using the predicted energy savings for each 

aseline level relative to the same target as above (i.e., 1.2 L/s-m2

 at 75 Pa (0.24 cfm/ft2 at 0.3 in H O)) and 

the baseline and target whole building air leakage values. As seen in Appendix A, the existing air leakage 

measurement cover a large range of air leakage values. To investigate the impact of the particular va

used in the study, sensitivity analyses were performed on each of these values for the frame office bu

in St. Louis (the middle climate studied). First, the whole building air leakage rate used for the baseline 

case was varied in steps over the range of 2.8 L/s-m2

 at 75 Pa to 9.0 L/s-m2 at 75 Pa (0.55 cfm/ft2 at 0.3 in

H2O to 1.8 c

b 2

the costs for option 1 in Table 5. As expected, Figure 13 shows the scalar ratio dropping as the baseline 

leakage increases. In other words, the energy savings of a building at the target airtightness relative to a 

tighter baseline building is smaller than the energy savings at the target airtightness relative to a leakier 

baseline building. However, the figure shows that even if the baseline leakage were set far lower than the 

9.1 L/s-m2

 (1.8 cfm/ft2) assumed in this study for St. Louis, the resulting scalar ratio would still be below 8

for this building and climate combination. For example, if the baseline building leakage rate were set at 4.2

L/s-m2 (0.8 cfm/ft2), which is the average of U.S. office buildings measured in past NIST studies, then the 

calculated scalar ratio would be about 3.3. 

6

7

8

0

1

2

3

4

.0 4.0 6 7.0 9.0

il ng A (L 5 P

Scalar Ratio

Depe scal on seli kage

rcise erformed in which the baseline air leakage rate was held s e val

is study but the target air leakage value was varied over a range of 1.2 L/s-m2

 at 75 Pa to 2.8 L/s-m2 at 75 

used

5

0.0 1.0 2 3.0 5.0 .0 8.0 10.0

Whole Bu di ir Leakage Rate /s·m2 @ 7 a)

Figure 13 ndence of ar ratio ba ne air lea rate

A similar exe was p teady at th ue used in

th

Pa (0.24 cfm/ft2

 at 0.3 in H2O to 0.55 cfm/ft2 at 0.3 in H2O). As above, simulations were performed for the

frame office building in St. Louis to estimate energy savings and the cost for option 1 in Table 5 were

to calculate the scalar ratios. While the predicted scalar ratio does increase with the target air leakage rate,

Figure 14 shows that the scalar ratio is relatively insensitive to the target air leakage rate over the range

studied for this building and climate combination. Specifically, if the building with the air barrier is 

assumed to be 2.33 times as leaky as the target of 1.2 L/s-m2

 at 75 Pa (0.24 cfm/ft2 at 0.3 in H2O) assumed 

in this study, the predicted scalar ratio increases by only 20 % and remains far below 8. 

32 
2.0

0.4

0.6

0.8

1.0

Scalar Ratio1.2

1.4

1.6

1.8

0.0

0.2

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8

Target Building Air Leakage Rate (L/s·m2 @ 75 Pa)

3

Figure 14 Dependence of scalar ratio on target air leakage rate

33 
Discussion

This simulation study included a small number of building types with a specific set of energy-related 

parameters (i.e., envelope construction types, internal loads, ventilation rates, etc.) in a limited set of

climates. Predicted potential annual heating and energy cost savings for these buildings ranged from 2 % to

36 % with the largest savings occurring in the heating-dominated climates of Minneapolis and Bismarck 

and the smallest savings occurring in the cooling-dominated climates of Phoenix and Miami. The cost

effectiveness analysis utilized costs for certain specific materials but other materials may be used to achieve

the whole building airtightness target level used in the study. 

Only a few other reports of the energy impacts of infiltration in commercial buildings and the potential 

savings due to tightening could be found for comparison. For the most part, these other studies are not as 

detailed as the current effort and may employ building configuration, airtightness, and other parameters that

vary significantly from this study but they do provide some reference for comparison. 

Potter et al. (1995) estimated the heating load due to infiltration for two U.K. office buildings of 

approximately equal size. They found that a 63 % reduction in air leakage could result in a reduction in

annual heating energy loss due to infiltration of about 300 MW/m2

. Since whole building energy analysis 

was not performed, this is not directly equivalent to the heating energy savings predicted in this study but it

does concur with the potential large impact of building airtightness on heating energy use. 

Edwards (1999) reported a modeling study of the ventilation and infiltration energy impacts in a 10-story 

apartment building in a range of Canadian climates. This study employed the CONTAM multizone airflow

model to create a model of an actual tested building and estimated that infiltration would be responsible for 

31 % to 46 % of the average peak heating load (based on measurements in four Toronto apartment

buildings reported by Scanada 1991). While the potential savings due to envelope tightening of 40 % to 

43 % calculated for Bismarck and Minneapolis predicted in the current study are not directly comparable, 

the impact of infiltration on heating loads are of a similar magnitude. The Scanada report estimated that 

infiltration contributed an average of 32 % of the annual heating load in those buildings. 

Building Sciences LTD presents an estimate of potential annual heating savings for an industrial building in

London of 60 MJ/m2

 due to a reduction in envelope leakiness of 75 % (http://www.airleakage.co.uk/why.htm). The gas savings for the target level relative to the baseline level in St. Louis (the

closest climate) estimated in this study ranged from 56 MJ/m2

 to 130 MJ/m2 depending on the building 

type. Again, these estimates are for different buildings with different assumptions but the magnitude of 

savings falls within the same overall range. 

Parekh (1992) described measured airtightness and monitored energy before and after sealing efforts in two 

existing high-rise residential buildings in Canada. The air leakage of the buildings was reduced by an 

average of 35 %, which resulted in an average heating energy consumption reduction of 9 %. While the 

energy saving is smaller than predicted in this study, the difference is readily explained by the modest

reduction in air leakage achieved for this retrofit study. 

Similarly, Shaw and Reardon (1995) reported an 11 % reduction in monitored heating energy consumption 

after a 43 % improvement in measured airtightness of a 20-story office building in Ottawa. Again, the 

in this study but the differences are easily explained 

duction in air leakage achieved in this retrofit study. 

s mentioned above, this study included a limited set of building-climate combinations and this work could 

be extended in a variety of ways. Specific recommendations for future work include:

• Continue study to develop more refined (i.e., climate-specific) airtightness targets, 

• Extend study to other building categories, 

• Perform factorial analysis to examine the potential interaction between airtightness and other 

building parameters, 

measured energy savings is smaller than the estimates 

by the different building type and the more modest re

 

A

34 
• Test airtightness of buildings built to a tightness standard (possibly in MA) to evaluate whether 

tightness targets are being met in practice, 

• Analyze the costs and potential energy savings from tightening of existing buildings and develop 

recommendations for the existing building stock, 

• And, develop diagnostic protocols and tools for failures of building envelopes that deteriorate IAQ

and energy efficiency.

Acknowledgements 

This work was sponsored by the US. Department of Energy, Office of Building Technologies under 

Interagency Agreement No. DE-AI01-01EE27615. The authors wish to acknowledge the efforts of Terry

Logee of DOE, Merle McBride and the ASHRAE SSPC90.1 Envelope Subcommittee in support of this 

project. 

35 
References 

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Cohen, R. 2003. “Tightly knit.” Building Services Journal, June 2003. 

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A

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Edwards, C. 1999. Modelling of Ventilation and Infiltration Energy Impacts in Mid- and High-Rise 

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E.

orida. 

. Building Services 

Res ch

Pros racteristics, Test Methods and Specifications for Large 

Buil g

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Buildings Using Multizone Airflow Simulation.” IAQ and Energy ’98, American Society of Heating,

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37 
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STP 125

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4072. Na

38 
Appendix A C

able A1 summa

ommercial Building Airtightness Data

rizes the measured whole building envelope airtightness data that was considered in

nalyzed by Persily (1998), however some additional buildings were added. The air leakage values in the 

r

ber of stories, or building floor area was not available for 

Data

Building type Year of Construction Stories Floor area Air leakage 

(0.3 in w.g.) 

Ref

T

developing the airtightness levels for this study. The majority of this data was previously reviewed and

a

table are normalized by the area of the above-ground portion of the building envelope. Information on yea

of construction, building construction type, num

all buildings. 

Table A1 Summary Table of Measured Nonresidential Building Envelope Airtightness

Building

construction type at 75 Pa 

 m2 L/s-m2 cfm/ft2

 

Anchorage Office 1981 Concrete panel 6 48500 3.8 0.75 1 

0.46 1 

1977 Concrete panel 15 21600 3.4 0.67 1 

Huron Office 1978 Masonry 4 6900 1.1 0.21 1 

.80 1 

00 2.0 0.39 1 

5.2 1.03 1 

100 12.0 2.37 7 

92 3 22300 3.1 0.60 2 

Admin School <1992 3 8200 2 

7 2 

B chool <1992 3 5600 1.8 0.36 2 

0.17 2 

.66 2 

4.1 0.80 2 

0.19 2 

0.80 2 

S. Pines School <1992 3 4400 1.0 0.19 2 

2 

2 

4 2 

1970 Concrete panel 9 6.2 1.23 3 

7 3.1 0.61 3 

1970 Concrete panel 20 2.6 0.61 3 

0.67 3 

0.39 3 

0.39 3 

3 

3 

 

1.77 4 

NRCC-S-B School 1971 Masonry 1 1900 8.2 1.61 4 

NRCC-S-C School 1965 Masonry 1 3800 7.4 1.45 4 

Ann Arbor Office 1975 Masonry 4 5300 2.3

Columbia Office

Norfolk Office 1978 Masonry 8 18600 4.1 0

Pittsfield Office 1977 Masonry 2 18

Springfield Office 1982 Concrete panel 5 14600 

Overland Office 1990 Curtain 5 35

 

Albany School <19

0.7 0.15 

Argentine School <1992 3 700 2.9 0.5

ishop Ryan S

CLC School <1992 3 4600 0.9

Green Mtn. School <1992 3 2400 3.3 0

Green Gym School <1992 3 900 

Laurel School <1992 3 1500 1.0

Middle School <1992 3 7200 4.1

S. Tama School <1992 3 700 2.3 0.45

Russell School <1992 3 3300 3.0 0.59

Velva School <1992 3 5600 2.7 0.5

 

NRCC-A Office 

NRCC-B Office 1964 Concrete panel 1

NRCC-C Office 

NRCC-D Office 1971 Curtain 20 3.4

NRCC-E Office 1968 Curtain 21 2.0

NRCC-F Office 1973 Concrete panel 16 2.0

NRCC-G Office 1974 Concrete panel 25 2.8 0.55

NRCC-H Office 1974 Curtain 20 1.4 0.27

 

NRCC-S-A School 1970 Concrete panel 1 2700 9.0 

39 
NRCC-S-D School 1973 Masonry 1 3500 12.3

NRCC-S-E School 1957 Masonry 1 3700 7.1 1

2.41 4 

.41 4 

1.25 4 

4 

4 

2.25 4 

1.65 4 

3200 5.5 1.09 4 

 

1.77 5 

1.37 5 

tail 1978 Masonry 3 19.8 3.90 5 

2 5 

5 5 

tail 1955 Masonry 3 17.0 3.34 5 

7.4 3.42 5 

anel 3 14.1 2.77 5 

RCC-RM Retail 1957 Masonry 3 5.7 1.13 5 

 19.4 3.82 5 

 

 2.4 0.47 14

0.41 14

ent 1981 Masonry 5 4.9 0.96 6 

3.1 0.61 10

BRE-2 Office 1963 Masonry 0.59 10

0.61 10

 6.7 1.32 10

3.8 0.75 10

1.01 10

1.71 10

BRE-8 Office 1971 Concrete panel 9.5 1.88 10

10.2 2.00 10

BRE-10 Office 1985 Concrete panel 11.6 2.28 10

0.72 13

V Elizabethan Masonry 3 4.3 0.83 13

0.85

13

w/ 2 

2.14

13

panels on 

.07

13

masonry 8.5 1.67

13

.84

13

wall/brick 4.3 0.85

13

NRCC-S-F School 1952 Masonry 1 3100 6.3 

NRCC-S-G School 1968 Masonry 1 5400 5.9 1.17 

NRCC-S-H School 1965 Masonry 1 5200 4.9 0.96 

NRCC-S-I School 1968 Masonry 1 2600 11.4

NRCC-S-J School 1972 Masonry 1 3000 8.4

NRCC-S-K School 1968 Masonry 1 

NRCC-BH Retail 1957 Masonry 3 9.0

NRCC-CK Retail 1963 Masonry 3 6.9

NRCC-HC Re

NRCC-MD Retail 1977 Masonry 3 18.4 3.6

NRCC-MK Retail 1967 Masonry 3 9.4 1.8

NRCC-MS Re

NRCC-OD Retail 1979 Concrete panel 3 1

NRCC-PO Retail 1979 Concrete p

N

NRCC-WG Retail 1954 Masonry 3

Parekh1 Apartment <1992 21 

Parekh2 Apartment <1992 10 2.1

NRCC-R Apartm

 

BRE-1 Office 1980 Masonry

 3.0

BRE-3 Office 1991 Masonry 3.1

BRE-4 Office 1965 Masonry

BRE-5 Office 1987 Masonry

BRE-6 Office 1990 Masonry 5.1

BRE-7 Office 1990 Masonry 8.7

BRE-9 Office 1986 Masonry

 

BSRIA-1 OfficeNV 1970 Prefab panels 2 3.7

BSRIA-2 OfficeN

BSRIA-3 Office 1991 Steelframe w/

masonry

6 

 4.4

BSRIA-4 Office 1987.5 Steelframe

masonry 10.9

BSRIA-5 OfficeNV 1963 Concrete 7 

frame 5.4 1

BSRIA-6 Office 1991 Steelframe w/ 3 

BSRIA-7 Office 1986 Steelframe w/

masonry

6 

 14.5 2

BSRIA-8 Office 1989 Curtain 5

40 
BSRIA-9 Office 1991 Steelframe w/

masonry

2 

 6.9 1.36

13

SRIA-10 Office 1990 Steelframe w/ 3 

1.22

13

elframe w/

masonry

3 

 11.8 2.31

13

ame w/

masonry

3 

 13.5 2.64

13

0.52 11

<1999 Curtain 64 270000 2.8 0.55 11

 

0.32 9 

1.55 9 

3 Healthcare 1992 Masonry 1 260 13.2 2.59 9 

0.61 9 

310 10.9 2.15 9 

6 Office 1961 Masonry 2 1180 3.2 0.62 9 

7 School 1968 Masonry 1 1570 7.8 1.54 9 

8 Office 1981 Masonry/frame 1 80 12.3 2.43 9 

9 Healthcare 1959 Masonry 1 140 7.4 1.45 9 

10 Office 1986 Masonry 1 570 7.5 1.47 9 

11 Industrial 1960 Masonry/metal 1 170 15.2 3.00 9 

12 Sports 1987 Masonry 1 1550 6.4 1.27 9 

13 Daycare 1970 Masonry 1 240 17.3 3.40 9 

14 School 1990 Manufactured 1 160 4.2 0.82 9 

15 Healthcare 1986 Masonry 1 190 6.4 1.25 9 

16 Office 1988 Manufactured 1 460 4.3 0.84 9 

17 School 1975 Masonry 1 1550 5.5 1.08 9 

18 Assembly 1986 Masonry 2 2090 3.6 0.71 9 

19 Restaurant 1975 Frame/masonry 1 180 7.7 1.52 9 

20 Office 1969 Masonry 1 270 3.8 0.76 9 

21 Healthcare 1987 Frame 1 240 12.0 2.36 9 

22 Restaurant 1994 Masonry 1 330 2.5 0.49 9 

23 Industrial 1984 Metal 1 280 14.0 2.75 9 

24 Library 1989 Masonry 1 800 1.2 0.24 9 

25 Sports 1987 Masonry 1 250 17.0 3.34 9 

26 Office 1994 Frame 1 90 19.7 3.87 9 

27 Office 1994 Frame 1 90 19.5 3.84 9 

28 Industrial 1994 Frame 1 180 13.5 2.66 9 

29 Office 1983 Manufactured 1 470 15.1 2.96 9 

30 Industrial 1941 Frame 2 300 27.0 5.31 9 

31 Restaurant 1986 Masonry 1 220 9.6 1.88 9 

32 Restaurant 1994 Frame 1 400 7.9 1.56 9 

33 Restaurant 1994 Masonry 1 290 8.2 1.62 9 

34 Office 1931 Frame/masonry 1 170 11.5 2.25 9 

35 Restaurant 1986 Masonry 1 310 4.4 0.86 9 

36 Industrial 1966 Masonry 1 1500 3.5 0.69 9 

37 Office 1972 Masonry 1 170 4.5 0.89 9 

38 Office 1972 Masonry 1 370 3.4 0.67 9 

B

masonry 6.2

BSRIA-11 OfficeNV 1992 Ste

BSRIA-12 Office 1992 Steelfr

 

PSU-1 Library <1999 Curtain 6 12077 2.6

PSU-2 Office

 

Florida 

1 Office 1965 Masonry 1 500 1.6

2 Assembly 1965 Masonry 1 460 7.9 

4 Assembly 1970 Masonry/frame 2 980 3.1

5 Assembly 1959 Masonry 1

41 
39 Office 1946 Masonry 1 200 9.6 1.89 9 

2.95 9 

2.32 9 

.91 9 

8 9 

.44 9 

Industrial 1966 Frame/masonry 1 240 12.5 2.46 9 

6.81 9 

47 Sports 1966 Frame/masonry 1 90 12.7 2.51 9 

50 Retail nry 1 90 20.8 0 9 

51 Office 1951 Masonry 1 500 9 

52 Office 1964 Masonry 1 9 

53 Industrial 1986 M al 260 3.5 0.69 9 

1

I

I

R t

6 Of ce 1990 Masonry 620 2.1 0.40 

Masonry

Masonry

Masonry

Masonry

Masonry

Masonry

Masonry

ELEM. SCHOOL 1 

40 School 1966 Frame/masonry 1 230 15.0

41 Animal 1966 Frame/masonry 1 70 11.8

42 Office 1966 Frame/masonry 1 590 14.8 2

43 Bar 1966 Frame/masonry 1 200 20.7 4.0

44 Office 1966 Frame/masonry 1 120 17.5 3

45

46 Office 1966 Frame/masonry 1 350 34.6

49 Retail 1966

1966 Fram

Frame/masonry

e/maso

1 90 8.9 1.75

4.1

6.6 1.30

9 

170 3.4 0.66

et 1 

54 Office 1976 Masonry 1 240 1

8.6

.6 2.29 

1.69

9 

55 ndustrial 1978 Metal 1 930 9 

56 ndustrial 1983 Metal 1 1150 5.6 1.10 9 

57 Sports 1982 Masonry 1 660 15.3

3.3

3.00

0.64

9 

58 Retail 1994 Masonry 1 430 9 

59 Retail 1973 Masonry 1 150 9.9 1.95 9 

60 Office 1985 Manufactured

Ma ed

1 80 4.3 0.86 9 

61

6

Office

esta ran

1983

19 3

nufactur

Frame

1

1

120

730

9.0

5.3

1.78

1.04

9 

2 9 

3

u

fi

6

1 9 

64 School 1965 1 940 3.1 0.61 9 

65 School 1965 1 190 3.0 0.59 9 

66 School 1965 1 470 9.1 1.79 9 

67 Hotel 1977 1 1400 6.7 1.32 9 

68 Hotel 1977 2 1180 6.3 1.24 9 

69 Retail 1989 1 400 10.9 2.16 9 

70 Retail 1969 1 230 1.1 0.22 9 

FSEC2

1 1966 MAS NRY 4

CHIC ST.

O 1 657.9 40.0 7.85 12

2 KEN RE 1993 MASONRY 2

COMMUNITY ENTE

1 93.66 3.7 0.73 12

3 C R 1991 MET/FRAME 2223.5 1

ELEM. SCHOOL 2

1 01.6 19.93 12

4 1998 MET/MAS

ELEM. SCHOOL 3

1 464.5 41.8 8.21 12

5 1998 MET/MAS

REST.

1 464.5 46.5 9.13 12

6 SEAFOOD 1998 FRAME 762.15 28.2 5.54 1

RIVER FRONT REST.

1 2

7 1986 MASONRY 2 543.47

STEAK REST.

3.8 0.74 12

8 HOUSE 1995 MET/FRAME 1 568.08

MDL. SCHOOL 1 B

29.1 5.70 12

9 1996 FRAME 1 65.587

MDL. SCHOOL 1 SW

6.1 1.20 12

10 1991 FRAME 1 60.385

MDL. SCHOOL 1 D

3.9 0.77 12

11 1991 FRAME 1 70.232

MDL. SCHOOL 1 E

5.3 1.05 12

12 1991 FRAME 1 70.232

MDL. SCHOOL 2 1

11.6 2.27 12

13 1997 FRAME 1 66.888

MDL. SCHOOL 2 6

12.0 2.36 12

14 1997 FRAME 1 66.888

15 MDL. SCHOOL 2 7

13.9 2.72 12

1997 FRAME 66.888 19.9 3.89 1

16 BAR AND GRILL

1 2

1985 MASONRY 1 222.96 9.5 1.87 12

17 CONVEN. STORE 1988 MASONRY 1 4

OCEAN FRONT REST.

01.33 10.1 1.98 12

18 1962 FRAME 1 555.26 27.3 5.36 12

42 
19 GREEK REST. 1960 M 1

CHAR FICE

ASONRY 1 39.35 35.7 6.99 12

20 ITY OF 1984 MET/MAS 3

O

l parame orted fo uildi

s for Me Airtightn ta

A.K. and ot. 1986. "Pr tion Fede Buildi easured

uildings STP 904, H schse agu ds., Am Society Test

s, Philadel

, T., Turn Fisher, G., T on, B. gman. 1992. "Fan Pressurizat

ings," Th erformance xteri es of ildings V, ASHRAE, nta,

G.T. and aw. 1976. "Studies on Ex ll Air Tightness an Air Infiltr of T

ASHRAE ctions, Vol. pp. 1

.Y. and L 1979. "Air T ss and Air Infiltration of School Buildings," ASHRAE 

, Vol.85, pp. 85-95.

.Y. 1981. ghtness: Sup ets an g Ma AE Journal, 198

pp.44-46 

6. .Y., Ma ousseau. 1991. "Overal and Com Airtightness Valu a Fi

S tment B RAE Tr ns, Vol.97, Part 2, pp.347-353. 

7. Persi , A.K., Dol nger, S.J. and S. Kirchner. 1991. "Preliminary R sults of the

E ental Evalu the Federal R s Cent land M ssouri," NISTIR 4634. 

8 n, L.I. 1986 akage in Ind Build cripti pm ," Measured

Leakage of Buildings, ASTM STP 904, H schse agus Eds., Ame ety for Testing

a als, Philad p. 101-105.

9 ings, J.B., W C.R., Moyer, N., Fairey, cKendry. 1996. ncontrolled Ai ow

in sidential Bu -CR-878-96, Flori ergy enter. 

10. Perera, M.D.A.E. erson, J., an e le Air Leakage Predictor for O

B ng e Airtightness During re R furbishment. CIBSE Nat

Conference. 

.P., Yuill, G.K. and B.W 999 Fi Testing o Tall Buildings

Envelop ge Rate Tra Vol. (2).

12. Cummings, J.B., Shirey, D.B., Withers, C., Raustad . Moyer. 2000. Evaluating the Impacts of

Perfo ro ommercial and Institutional

Buildings, Final Report, FSEC-CR-1210-00. 

13. Potter, I., Jones, T., and W. Booth. 1995. TechNote eakage of Office Buildings. Building

Services Research and Information Association. 

14. Parekh, A. 1992. 'Power Demand and Energy Savings Through Air Leakage C rol in High-R

Buildings Climates'. P ing rformance of the Exterior Envelope of 

Buildings V. 

1 47.54 19.9 3.91 12

verall mean 9.7 1.9

Note: Not al ters were rep r some b ngs. 

Reference asured ess Da

1. Persily, R.A. Gr essuriza Testing of ral ngs," M Air

Leakage of B

and Material

, ASTM

ph a, pp. 184-200. 

.R. Tre l and P.L. L s, E erican for ing 

i

2. Brennan er, W., homps , and B. Li ion of

School Build ermal P of the E or Envelop Bu Atla pp.

643-645. 

3. Tamura, C.Y. Sh terior Wa d ation all

Buildings," Transa 82 (II), 22-34.

4. Shaw, C . Jones. ightne

Transactions Part 1,

5. Shaw. C "Air Ti ermark d Shoppin lls," ASHR March 1,

 Shaw, C

tory Apar

gee R.J. and J. R

uilding," ASH

l ponent es of veansactio

ly s, W.S., Nabi e

nvironm ation of ecord er in Over i

. Lundi . "Air Le ustrial ings - Des on of Equi ent Air 

.R. Tre l and P.L. L , rican Soci

nd Materi elphia, p

. Cumm ithers, P., and B. M U r Fl

 Non-Re ildings, FSEC da Solar En C

S., Hend d B.C. W bb. 1997. Simp ffice

uildings: Assessi Envelop Design or Befo e ional

11. Bahnfleth, W . Lee. 1 . "Protocol for eld f to

Determine e Air Leaka ," ASHRAE nsactions, 105

, R. and N

Uncontrolled Air Flow and HVAC rmance P blems on Florida's C

 8/95 Air L

ont ise 

Residential in Cold roceed s of Thermal Pe

43