The energy required to heat and cool outdoor air and infiltration air is a significant fraction of thermal loads. This project has developed diagnostic procedures to identify air leaks and methods to calculate the savings from air sealing large commercial and institutional buildings. Envelope air sealing could significantly reduce large building energy consumption, but no systematic research has identified the most cost-effective strategies for Minnesota buildings.

2. s
The Value of Air Leakage Testing
in Large Commercial Buildings
An Overview of Study Findings
November 7, 2013
Technical Difficulties:
Anna Jursik at ajursik@mncee.org
Dave Bohac P.E. | Director of Research

3. Counting the Capacity that Didn't Hatch: The Rate
Mitigation Effect of DSM Programs
This webinar will provide an analysis overview, highlighting how
the effects on revenue differ from the levelized cost calculations
currently used, and how historical and ongoing benefits from
DSM program activity might be framed in the future.
Jenny Edwards
Innovation Exchange
Program Manager
Target Audience
• Utility DSM managers
• Energy policy experts
• Policy-makers
Thursday, Dec. 12th
11:00 – 12:00 CST
Register at
www.cee.org/Innovation-Exchange

4. s
The Value of Air Leakage Testing
in Large Commercial Buildings
An Overview of Study Findings
Dave Bohac P.E. | Director of Research

5. Acknowledgements
This project was supported in part by a grant from
the Minnesota Department of Commerce, Division of
Energy Resources through a Conservation Applied
Research and Development (CARD) program

6. Large Building Tightness Specification
• Measure the air flow rate needed to pressurize &
depressurize the building by 75Pa (0.3 in. wc.)
• Divide by the building envelope area – typically
the exterior walls + roof + floor (6 sides)
• Results from 387 US C&I buildings
o Average = 0.72 cfm/ft2
o Range 0.03 – 4.3 cfm/ft2

7. Code Requirements
• US Army Corp Engineers = 0.25 cfm/ft2
o Tested over 300 buildings
o Average = 0.16 cfm/ft2
• IECC 2012 (7 states) whole building compliance
path = 0.40 cfm/ft2
• Washington State: Buildings over five stories
require a whole building test, but do not have to
pass a prescribed value.
• City of Seattle : All buildings require a whole
building test, but do not have to pass a
prescribed value.

8. Why do we care about building air leakage?
• HVAC systems pressurize buildings to
eliminate infiltration – don’t they?
• When HVAC is off => air infiltration
• Pressurization not always effective or
implemented correctly
• NIST/Persily tracer gas results –
infiltration can be significant

9. Air Handler Pressurization
=10,500 – 2,075cfm
10,500 cfm
2,075 cfm
4 Story 60,000sf Office Building: leakage = 27,000 cfm@75Pa, 0.5 cfm@75/ft2

10. Roof Top Unit Operation
2,075 cfm
10,500 cfm

11. Single-zone Constant Volume AHU
• Supply and Return Fans turn on/off by schedule
• Outside Air Damper has a minimum position setpoint for
ventilation
• Relief Damper controls air exhausted from the building
Relief Air
2,075 cfm – Exhaust Fans
Relief Air
Damper 25%
open
Mixed Air
Damper 75%
open
Outside Air
10,500 cfm
From Space
Return Fan
MAT Sensor
DAT Sensor
Outside Air
Damper 25%
open
To Space
Supply Fan
Heating Coil
Cooling Coil

12. Air Handler Pressurization
10,500 cfm
2,075 cfm
4 Story 60,000sf Office Building: leakage = 27,000 cfm@75Pa, 0.5 cfm@75/ft2

13. Air Handler Pressurization
10,500 cfm
2,075 cfm
4 Story 60,000sf Office Building: leakage = 27,000 cfm@75Pa, 0.5 cfm@75/ft2

14. Air Handler Pressurization
10,500 cfm
2,075 cfm
Infiltration >>
4 Story 60,000sf Office Building: leakage = 27,000 cfm@75Pa, 0.5 cfm@75/ft2

15. Single-zone Constant Volume AHU
• Economizer operation
o Mild weather when building needs cooling
o Open outdoor air dampers, exhaust dampers follow;
OA – EA stays the same?
Relief Air
16,175 cfm – Exhaust Fans
Relief Air
Damper 60%
open
Mixed Air
Damper 40%
open
Outside Air
24,600 cfm
From Space
Return Fan
MAT Sensor
DAT Sensor
Outside Air
Damper 60%
open
To Space
Supply Fan

16. Variable Volume AHU with VAV Boxes
• Supply and Return Fans
o Supply fan VFD modulates to meet Duct Static
Pressure (DSP) Setpoint
o Return fan lags supply fan to maintain positive pressure
V
F
D
Return Fan
77% speed
V
F
D
DSP Sensor
(typically 2/3 down
supply duct)
Supply Fan
87% speed

17. Model Infiltration: Range of Flow Imbalance
Minimum outside air = 20,300cfm
1 Story 60,560ft2 Elementary School: leakage = 44,670 cfm@75Pa (0.75cfm@75/ft2)

18. Model Infiltration: Range of Flow Imbalance
Minimum outside air = 20,300cfm
1 Story 60,560ft2 Elementary School: leakage = 14,890 cfm@75Pa (0.25cfm@75/ft2)

19. Model Infiltration: Range of Flow Imbalance
Envelope Leakage= 0.75 cfm@75Pa/ft2
Avg Infil. (cfm)
Avg Infil. (ach)
Heat Load (therms/yr)
% Space Heating
Cost ($)
-3,450
2,986
0.25
7,264
19%
$4,213
HVAC Flow Imbalance, OA - EA (cfm)
0
3,450
6,900
2,444
2,077
1,849
0.20
0.17
0.15
6,114
5,260
4,732
16%
14%
12%
$3,546
$3,051
$2,745
17,250
1,652
0.14
4,308
11%
$2,499

20. Model Infiltration: Range of Flow Imbalance
Envelope Leakage= 0.75 cfm@75Pa/ft2
Avg Infil. (cfm)
Avg Infil. (ach)
Heat Load (therms/yr)
% Space Heating
Cost ($)
-3,450
2,986
0.25
7,264
19%
$4,213
HVAC Flow Imbalance, OA - EA (cfm)
0
3,450
6,900
2,444
2,077
1,849
0.20
0.17
0.15
6,114
5,260
4,732
16%
14%
12%
$3,546
$3,051
$2,745
17,250
1,652
0.14
4,308
11%
$2,499
Envelope Leakage= 0.25 cfm@75Pa/ft2
Avg Infil. (cfm)
Avg Infil. (ach)
Heat Load (therms/yr)
% Space Heating
Cost ($)
-3,450
1,725
0.14
4,004
10%
$2,322
HVAC Flow Imbalance, OA - EA (cfm)
0
3,450
6,900
951
708
678
0.08
0.06
0.06
2,439
1,875
1,813
6%
5%
5%
$1,414
$1,087
$1,052
17,250
676
0.06
1,809
5%
$1,049

21. Air Leakage Test Video

22. How leaky or tight are US buildings?
• Test results compiled by the National Institute
of Standards and Technology (NIST) –
Emmerich and Persily – over the past 15
years
• 387 commercial and institutional buildings
• NOT RANDOM: researchers, low-energy
programs, private testing firms
• Used to model air infiltration energy loads
and help establish leakage standards

23. NIST Results from US whole building tests
6-sided at 75Pa (cfm/ft2)
Mean Std Dev
Min
0.35
0.38
0.03
0.29
0.20
0.06
0.40
0.15
0.11
0.54
0.40
0.05
0.30
0.23
0.09
0.36
0.30
0.03
Dataset
Efficiency Vermont
ASHRAE RP 1478
Washington
Other VT/NH
Other
All new data
Qty
36
16
18
79
10
159
All previous data
228
0.92
0.70
0.09
4.28
All Buildings
387
0.72
0.63
0.03
4.28
USACE & Navy
300
0.16
Emmerich and Persily 2013
USACE Std = 0.25
Max
1.78
0.75
0.64
1.73
0.75
1.78

24. NIST Results: Frequency Histogram
USACE Std = 4.5
20-25% meet Std
Multiply by 0.055 >> cfm/ft2
Emmerich and Persily 2013

25. NIST Results: Weak Trends
• Tighter – office, education, public
assembly & long-term health care
• Leakier – retail, restaurants, industrial
• Leakier exterior walls – frame,
masonry/metal, & frame/masonry

26. NIST Results: Effect of Building Size
Buildings > 54,000ft2 twice as tight
0.55 cfm/ft2
Emmerich and Persily 2013

27. NIST Results: Effect of Climate
Heating degree days > 3,600 one third tighter
0.55 cfm/ft2
Emmerich and Persily 2013

28. NIST Results: Effect of Age
138 buildings with no air barriers built since 1950 – no strong trend
Colder climate
0.55 cfm/ft2
Emmerich and Persily 2013

29. NIST Results: LEED Buildings
• 23 LEED buildings; average = 0.29 cfm/ft2
• Significantly tighter than average of other
364 buildings
• Slightly (5%) leakier than other 56
buildings with an air barrier

30. NIST Results: Effect of Air Barrier
Buildings with air barrier are 70% tighter
Page 30
USACE Std = 4.5, 0.25cfm/ft2
Emmerich and Persily 2013

31. NIST Results: Effect of Air Barrier
Compare no air barrier to tight construction
0.1 cfm/ft2
Page 31
1.0 cfm/ft2
USACE Std = 4.5, 0.25cfm/ft2
Emmerich and Persily 2013

32. NIST Building Infiltration & Energy Models
• Multizone infiltration and energy model
• Compared air infiltration and energy use
for:
o “typical” - no air barrier reported
leakage (4x USACE)
o “target” – good practice (40% below
USACE)
• Five cities in different climate zones

33. NIST Building Infiltration & Energy Models
Two-Story, 24,000ft2 Office Building
One-Story, 12,000ft2 Retail Building
Emmerich and Persily 2013
Page 33

34. Model Infiltration: Range of Envelope Leakage
Minimum outside air = 20,300cfm
1 Story 60,560ft2 Elementary School: HVAC Imbalance = 3,450 cfm

35. Model Infiltration: Range of Envelope Leakage
1 Story 60,560ft2 Elementary School: HVAC Imbalance = 3,450 cfm
Avg Infil. (cfm)
Avg Infil. (ach)
Heat Load (therms/yr)
% Space Heating
Cost ($)
0.05
305
0.03
855
2%
$496
NIST office building model:
1.0 cfm/ft2 = 0.23 ach
0.1cfm/ft2 = 0.05 ach
0.1
417
0.03
1,139
3%
$661
Building Envelope Leakage (cfm@75/ft2)
0.15
0.25
0.4
0.75
481
708
1,094
2,077
0.04
0.06
0.09
0.17
1,305
1,875
2,832
5,260
3%
5%
7%
14%
$757
$1,087
$1,643
$3,051
1.25
3,539
0.29
8,867
23%
$5,143
2
5,751
0.47
14,322
37%
$8,306

36. Minnesota Leakage Study: work scope
• Conduct investigations on 25 buildings: floor area of
25,000 to 500,000 ft2
• Air seal and pre/post leakage tests on X 7 buildings
6
• Continuous building pressure and HVAC operation
data for 50 to 200 days
• CONTAM pre/post air flow models that include
mechanical system leakage and pressure effects
• Compute infiltration/energy reductions

37. Building Characteristics
Floor
#
Constr
Building ID
Area (sf) Stories
Elem School TF
59,558
1
Middle School
138,887
3
Small Office
26,927
1
Univ Library
246,365
3
Elem School PS
60,968
1
Library/Office
55,407
1
Year
1951
1936
1998
1967
1965
2007
Wall Type
Masonry & corrugated metal panel
Cast concrete w/CMU infill
EFIS tip up (3 walls) and CMU block
Cast concrete w/CMU infill & brick ext
CMU w/brick exterior
Steel studs & brick or stone cladding
3 elementary &
middle schools:
1936 to 1965 with
additions
60,000 – 139,000sf
University Library 246,000sf
Small Office 27,000sf
Library/Office 55,000sf

38. Minnesota Leakage Study: leakage results
All 7 buildings at least 25% tighter than the US Army Corp standard of 0.25 cfm/ft2
Envelope
Floor
Area (ft2)
Air Leakage at 75Pa
6 Sides
Building ID
Area (ft2) 6 Sides2
(cfm) (cfm/ft2)
Elem School TF
59,558
146,977 27,425
0.19
Comm. College
95,000
164,844 28,881
0.18
Middle School
138,887
208,733 32,818
0.16
Small Office
26,927
65,267 9,177
0.14
Univ Library
246,365
171,712 23,356
0.14
Elem School PS
60,968
145,766 17,602
0.12
Library/Office
55,407
139,965 12,321
0.09
Minimum
26,927
65,267
9,177
0.09
Mean
97,587
149,038
21,654
0.14
Median
60,968
146,977
23,356
0.14
Maximum
246,365
208,733
32,818
0.19
EqLA
#
Constr
(ft2)
15.2
17.2
16.6
4.6
13.1
9.6
6.9
4.6
11.9
13.1
17.2
Stories
1
2
3
1
3
1
1
Year
1951
1996
1936
1998
1967
1965
2007

39. Comparison to US Buildings
7 building average is 85% less than the US average, slightly less than US Army Corp average
6 buildings

40. Tighter Buildings in Colder Climates?
7 building average is 85% less than the US average
6 buildings

41. Air sealing focused on roof/wall
Canopy leakage at exterior wall

42. Air Sealing Reduction
“Tight” buildings tightened by 9%
Air Leakage at 75Pa
(cfm)
Building ID
Elem School TF
Comm. College
Middle School
Small Office
Univ Library
Elem School PS
Library/Office
Minimum
Mean
Median
Maximum
Pre
27,425
28,881
32,818
9,177
23,356
17,602
12,321
9,177
21,654
23,356
32,818
Reduction
Post
22,699
28,133
28,872
8,470
21,963
15,837
11,369
8,470
19,620
21,963
28,872
(cfm)
4,726
748
3,947
708
1,392
1,765
953
708
2,034
1,392
4,726
(%)
17%
3%
12%
8%
6%
10%
8%
3%
9%
8%
17%
Leakier
Tighter
Air sealing work confirmed by visual, smoke puffer, and
IR inspections

43. Air Sealing Reduction
More expensive to seal tighter buildings?
Air Sealing Cost
Building ID
Elem School TF
Comm. College
Middle School
Small Office
Univ Library
Elem School PS
Library/Office
Minimum
Mean
Median
Maximum
Total ($/CFM75) ($/ft2)
$ 18,550 $
3.92 $ 6,822
$ 17,845 $ 23.86 $ 17,273
$ 23,700 $
6.00 $ 8,434
$ 4,768 $
6.73 $ 10,058
$ 15,918 $ 11.43 $ 65,159
$ 26,700 $ 15.13 $ 38,132
$ 1,152 $
1.21 $ 1,297
$ 1,152 $
1.21 $ 1,297
$ 15,519 $
9.76 $ 21,025
$ 17,845 $
6.73 $ 10,058
$ 26,700 $ 23.86 $ 65,159
Leakier
Tighter

44. Air Sealing Reduction
Contractor estimates better for leakier buildings?
Leakage Area
EqLA (ft2)
Building ID
Elem School TF
Comm. College
Middle School
Small Office
Univ Library
Elem School PS
Library/Office
Pre
15.2
17.2
16.6
4.6
13.1
9.6
6.9
Post
12.5
16.2
13.8
4.1
12.8
8.9
6.0
Sealed Area (sf)
Reduction
(ft2)
2.7
1.0
2.8
0.5
0.2
0.7
0.9
Contractor Estimated
(%) Roof/Wall
18%
8.84
6%
5.47
17% 11.73
10%
2%
7% 14.45
13%
Total
11.49
5.47
14.98
Meas/Est
0.31
0.19
0.24
Leakier
16.94
0.05
Tighter
Building Leakage < Estimated sealing

45. Air Sealing Energy Savings
Modeled Infiltration and Energy Savings
Space Heat Gas Use (Therms/yr)
Building ID
Elem School TF
Comm. College
Middle School
Small Office
Univ Library
Elem School PS
Library/Office
Avg
Leakage
Savings
Total Infiltration Infil/Total Infil (cfm) Red. (%) (Therm/yr) ($/yr)
40,224
3,468
9%
1,296
17%
811
$
470
32,095
5,168 16%
1,730
3%
88
$
53
44,469
14,950
34%
4,814
12%
1,397
$
810
8%
249
6%
35
$
18
26,563
3,530 13%
1,453
10%
325
$
188
18,108
4,194 23%
1,503
8%
170
$
109
Payback
Cost ($)
$ 18,550
$ 17,845
$ 23,700
$ 4,768
$ 15,918
$ 26,700
$ 1,152
Able to seal “tight” buildings, but work was not cost effective
(years)
39
339
29
904
142
11

46. Mechanical System Leakage
Part of building envelope when not operating
Mean
49%
0.06 cfm/ft2
(6 sides)
Range
17% to 103%
0.02 to 0.12 cfm/ft2
Two most recently built (1998 and 2007) had low leakage

47. Building Pressure Measurements
Average building pressure at ground level (Pa)
-20 < OAT < 0
unoccupied occupied
Comm. College
Elem School PS
Middle School
High School
Elem School TF
Library/Office
Sports Arena
Univ Class T
Univ Union
High Rise Office
Clinic 1
Clinic 2
Clinic 3
Univ Class SH
Maximum
Minimum
Median
-10
-4
-6
6
-11
-10
-49
0
6
-49
-6
-13
11
11
-13
-10
0 < OAT < 20
unoccupied occupied
-6
-4
0
-10
-4
-6
-6
-3
-11
0
0
-5
-2
1
-7
-4
0
-4
-11
-39
-9
-6
0
-39
-6
-5
-35
-11
11
11
-35
-4
20 < OAT < 45
unoccupied occupied
-2
-2
-6
-7
-3
-4
-4
0
-9
-48
-10
-27
-6
-3
0
-48
-5
3
4
-3
-3
2
-4
-1
3
2
-44
-2
-23
-6
9
9
-44
-2
45 < OAT <70
unoccupied occupied
0
0
-3
-6
-1
-2
-4
12
-7
-32
-9
1
12
-32
-2
12
4
2
4
3
2
9
12
8
-21
2
-11
1
7
12
-21
4
70 < OAT <90
unoccupied occupied
1
1
5
6
0
-3
1
1
-9
27
-6
-2
1
-1
1
-6
0
27
-9
1
No buildings operating greater than 10Pa at ground level
Most have higher pressure during occupied hours

48. Building Pressure Measurements
20F < outside temp <= 45F
Roof level pressures are higher – few operating greater than 10Pa

49. Building Pressure Measurements
20F < outside temp <= 45F
Roof level pressures are higher – few operating greater than 10Pa

50. Summary
•
•
•
•
•
•
Tight buildings: 85% tighter than U.S.
average & at least 25% below Army Corp
standard – due to cold climate location?
Sealing = 9% reduction, more reduction and
less expensive for leakier buildings
Contractor over-estimated sealing area
Long paybacks for air sealing work
Including mechanical systems increased
leakage by 17 to 103% (0.02 to 0.12 cfm/ft2)
HVAC systems tend to pressurize buildings.
Not as great as typical design practice

51. Additional Slides

52. ASHRAE Research: selection criteria
• Goal: 24 to 36 existing mid- and high-rise buildings (16
Completed)
• Non-residential
• 4 stories or higher
• Sustainability certification (14 of 16)
• Built after the year 2000
• Climate zones 2-7 (All 6 Zones Represented)

53. ASHRAE Research Project: leakage results
• Average = 0.29 cfm/ft2
• Green building = 0.32 cfm/ft2; others = 0.22 cfm/ft2
• Air barrier specified and envelope expert = 0.13
cfm/ft2; others = 0.39 cfm/ft2
• Unsealing HVAC penetrations increased leakage by
average of 27% with range of 2% to 51%

54. ASHRAE Research Project: leakage sites
• Roof/wall intersection
• Soffits and overhangs
• Mechanical rooms, garages,
basements, loading docks
• Roll-up and overhead doors

55. Single-zone Constant Volume AHU
• Supply and Return Fans
o On/Off according to schedule
o May cycle on to maintain night setback temperature
Return Fan
Supply Fan

56. Roof Top Unit Operation

57. What about Energy Recovery Ventilators?
• Why not run the exhaust air through an
ERV to recovery some of that energy
instead of forcing it out through the
envelope?
• Need a tighter envelope to accomplish
ERVs with infiltration control

58. Dave Bohac P.E.
Center for Energy & Environment | Director of Research
dbohac@mncee.org
Megan Hoye, LEED AP
Center for Energy & Environment | Engagement Coordinator
mhoye@mncee.org

60. Thank you!

61. 1. Three to four take aways
2. Tell them what to look for
3. Sdf..