Course / Learning Objectives: •Learn about the non-conformance in air-tightness standards and what's driving this non-consensus. •Examine case studies to realize the differences in air-tightness results as compared to air-tightness standards. •Recognize the importance of moisture control while achieving air tightness and understand the predictable elements of this process. •Apply predictable elements of air-barrier design that will mitigate failures.

1. The Predictability of Moisture
Control & Building Air
Tightness in High-
Performance Buildings
Course Number FR111
Friday, April 28, 2017 - 7:00 AM-8:00 AM
1.0 Learning Unit/HSW/GBCI/RIBA

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The statements expressed by speakers, panelists, and other
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them.
Questions related to specific products and services may be addressed
at the conclusion of this presentation.

4. Speakers List
Richard Scott, AIA, NCARB
Senior Forensic Architect/Vice-president Liberty Building Forensics
Group
Donald Snell, P.E., CMC, CIEC
Senior Forensic Engineer/Vice-president
Liberty Building Forensics Group

5. Course / Learning Objectives
• Learn about the non-conformance in air-tightness standards
and what's driving this non-consensus.
• Examine case studies to realize the differences in air-tightness
results as compared to air-tightness standards.
• Recognize the importance of moisture control while achieving
air tightness and understand the predictable elements of this
process.
• Apply predictable elements of air-barrier design that will mitigate
failures.

6. Why Are You Here at 7 AM?
• Codes/Energy Drivers
• Difficult to Spec, Construct & Test
• Risks

7. Presentation Outline
1. Introduction
2. Overview of Codes, Standards, & Research w/r/t Air
Leakage, Infiltration, & Moisture Control
3. Two Case Studies
4. Predictability of Moisture Control & Building Air
Tightness
5. Conclusions

8. Trade Winds & Poor Air Barrier
• Original Construction -
$100M
• Opened April 2001
• Closed July 2002
• Cost to remediate- $65M

9. Cold Climate Clean Room

10. Hotel-Charleston, SC
HVAC & Envelope problems
occurred immediately after opening
Over $10MM spent in repairs
including replacing all brick
Mold re-occurred following summer

11. Caribbean Resort
Mold growth less than 6
months after occupancy
Negative pressure and
interruptions in air barrier
$15MM renovation

12. 5-Star
Ski Resort
Exfiltration problems leads to
icicles inside soffits

13. Tongue & Groove Ceiling at SE 5 ⭐️ Resort
Lack of air barrier above T&G
ceiling allows hot & humid attic
air to infiltrate
into space

14. Common Elements: Pressure & Pathways
Pressure:
-HVAC or Wind
Pathways:
-Poor, misplaced
or missing
air barriers

15. Unintended Air Flows-Pressure & Pathways
Small pressures
(measured in Pascals)
over time combined with
infiltration of hot humid
air leads to mold growth
SE Resort: $40MM
repair cost

16. Mold Growth Can Be An Indicator

17. Moisture Mechanisms
•Liquid-Rain
•Gravity
•Capillary
•Wind
•Vapor-Air Infiltration
•Vapor-Diffusion
The Barriers
•Primary WRB
•Secondary WRB
•Thermal Barrier
•Air Barrier
•Vapor Retarder
The Three Moisture Mechanisms
& The Barriers That Control Them

18. The Requirements for each barrier differs
significantly
Preferred Location
within the Wall
System
Integrity Requirements
of the Compound
Rainwater Barrier Exterior side of the
stud cavity
Nearly Perfect, or must
have water-shedding
capabilities
Vapor Diffusion
Retarder
Exterior to the
Thermal insulation
As good as practical;
does not have to be
pinhole-free or have
joints taped
Air Barrier Anywhere in the wall
assembly; exterior
location preferred
Nearly perfect, and
imperfections must be
compensated by
positive pressurization
For Hot Humid
Climate

19. Different Materials Can Be Air Barriers
•Sheet goods:
•building wrap
•P&S
•polyethylene
•Fluid-applied membranes
•Spray polyurethane foam
•Exterior gypsum/fiberglass
sheathing
•Drywall
0.08 perm
28 perm
ABAA Air Barrier:
<0.02 L/(s-m2)@75 Pa

20. Public Building--Texas
Confusion about air barrier
during remediation rebuild

21. Flash and Batt
Structural Steel Stud Wall
Stucco
WRB
Gypsum sheathing
SPF
Thermal Barrier
Batt Insulation w/o VR
Gypsum Board

22. HVAC-Envelope relationship
HVAC Pressurization
Wall*
Unlikely
Unlikely
Possible
Possible
Unlikely
Possible Very
Likely
Very
Likely
*integrity of air barrier, rain barrier, and/or vapor retarder
Possibility of mold
in walls and space
due to HVAC &
envelope barrier
relationships
(hot humid climate)

23. High Performance
Building
LEED--Arkansas
Lessons Learned
•Air Leaks: It is more difficult to
seal a building against air leaks
than it is to agree to a leakage
target with a contractor. Actual
Air Leakage>5x the Design
High Performance Buildings – Winter 2008

24. Difficulties Testing Air Barriers
• Blower Door Setup Can Be Complex
• Generally Need Envelope Complete
– Too Late to Correct
• Not Always Clear What Failed
• Best Course of Action
– QA/QC during construction (checklists)
– Mockup Testing (stand alone or in
situ)
24

25. Section 2: Overview of Codes, Standards & Research: Air
Leakage, Infiltration, & Moisture Control
25

26. • Air Barrier
• Continuous Air Barrier
• Airtight Construction
• Building Air Tightness
• High Performance Green Buildings
26
Terms

27. Air Leakage Requirements in Codes - IECC
27

28. Air Leakage Requirements in Codes - FBC
28

29. US Mainland Climate Zones
29

30. Non- Consensus in Air Leakage Standards
Some Strides Have Been Made,
Non-Consensus Still Exists:
30

31. 31
Air Infiltration
Requirements
(cfm/ft2@0.3 w.g., 75 Pa)
Materials
(ASTM E2178)
Assemblies
(ASTM E2357 or E1677)
Whole Buildings
(ASTM E779)
ASHRAE 90.1 (2010) 0.004 0.04 --
USACE (2008)
NAVFAC (2011)
0.004 -- 0.25
GSA (2010)
USAF (2011)
0.004 0.04 0.40
IgCC (2012) --- --- 0.25
Air Leakage Standards

32. Non- Consensus in Air Leakage Standards
Other Current and Future Directions of the Code, Ordinances and
Information for Better and Worse:
• Air Leakage Rates
– ASHRAE STD 189.1-2011 – 0.40 CFM/SF at 75 Pa (Whole Building)
– IgCC (2012) – 0.25 CFM/SF at 75 Pa (Whole Building)
– USACE (Proposed, HBB) – 0.15 CFM/SF at 75 Pa (Whole Building)
• Sustainability Ordinance – City of Miami Beach
– Green Building Requirements – New > 7000 SF, Exist, Ground FL additions
to exist that encompass >10K SF
– Post sustainability fee prior to TCO, CO, CC whatever comes first. Valued at
5% of construction value of building permit. Eligible refund or partial
refund
32

33. Non- Consensus in Air Leakage Standards
FSEC
Complexity/Driver
s v. Risk of
Failure
33 Source: 1996 Florida Solar Energy Center (FSEC)
Complexity
DRIVERS
Mild
Intense
I “low”
II
“moderate
”
III “high”

34. Non- Consensus in Air Leakage Standards
Research Insights:
• Clear Difference in Performance w/
an Envelope Consultant
• How to Treat HVAC Penetrations in
ASTM E779-2010 Test?
• Common Air Leakage Sites
Identified
• NIST Study of Pre and Post 2000
Buildings
• No Buildings Located in Climate
Zones 1 and 2A
34

35. Non- Consensus in Air Leakage Standards
Some Strides Have Been Made, Non-Consensus Still
Exists:
• Terry Brennan Calls it “Mesmerizing Metrics”
• Where Does the Non-Consensus Exist
• Why Does the Non-Consensus Exist
35

36. Section 3: Two Case Studies
1. Tropical “Green” Resort
– Difficulty Testing
– Difficulty Meeting Performance
– Difficulty Determining Why
2. Midwestern Medical Facility
– Winter Condensation/Frost due to
AB/Pressurization/Humidification
– How Problems Solved W/Poor AB
36

37. Case Study #1: Air Tests Fall Short at Tropical Resort
37

38. 500+ Room Resort on Ocean
Goals:
•“Green” Sustainable & Energy Efficient
Building
•Minimal Outdoor Air Infiltration
•No Mold/Moisture Problems
38

39. Design Phase Peer Review
• Typical wall – stucco/lath on
sheathing/metal framing
• Air barrier goal:
0.085 cfm/ft2 @ 75 Pa
• Fluid-applied vs commercial building
wrap air barrier
39

40. Testing Limitations
• Stand-alone mock-up vs in situ testing
• Testing before envelope is complete
• Testing on an active construction site with
open walls and trades on test floors
• Wind influence
40

41. Test Room
Testing Procedure
41

42. Testing Procedure
42

43. Testing Procedure
Command Center
43

44. 44
Location Total Leakage Leakage to
Outdoors (cfm)
Leakage to
Outdoors (cfm/ft2)
Ratio to Designer
Target of 0.085
B-238 306 87 0.664 7.8
B-438 362 73 0.557 6.6
D-552 379 77 0.295 3.5
Total and Outdoor Leakage at 75 Pa
Summary of Test Results

45. 45
Comparison to Industry Standards
Low High or Average
Designer 0.085*
LBFG Testing 0.30 0.66
ASHRAE “tight” 0.10
ASHRAE “average” 0.30
ASHRAE “leaky” 0.60
Proskiw (9 high rise bldgs 15-25
stories)
0.47
Persily & Grot/ ASHRAE
Fundamentals 2005
0.21 1.03
Persily, “Myths About Envelopes”
(139 commercial >=15 stories)
0.22 0.66
ASHRAE 189.1 0.40
IgCC 0.25
Values in cfm/ft2 @ 75 Pa (Some standards converted to 75 Pa)
*No Buildings Have Been Reported This Low

46. Leak Points
46

47. Conclusions
• Ambitious target difficult to meet
• Target numbers meaningless/abstract
• Target more stringent than:
– ASHRAE 189.1 (0.40 cfm/ft2) only one met
– IgCC (0.25 cfm/ft2) none met
• Some infiltration acceptable w/HVAC positive
pressure
47

48. Lessons Learned
• Specify reasonable and achievable air barrier
requirements
• Provide better directions to workers
• Specify construction phase air tightness
testing
• Perform better quality control (QC)
inspections at critical phases
48

49. Lessons Learned
• Test sliding glass doors for air leakage
• Perform blower door testing at lower floors
after dry-in
• Perform exhaust duct and shaft leakage
testing
• Perform air balancing early during
construction when HVAC is first energized -
blower door testing provide data for balancing
49

50. Case Study #2: Thawing a Frosty Relationship
50

51. Midwestern Medical Facility
• 50 Bed
• Constructed 2006
• Humidification
added for comfort
51

52. Frost &
Condensation
52

53. Moisture Damage
53

54. • Improper design assumption on
air barrier at boundary condition
(envelope)
• Humidification improperly
controlled
• HVAC induced positive
pressurization based on
incorrect interpretation of state
requirements
Three Issues
Come Together
54

55. Repair Attempts
Fail to Solve Problem
55

56. Solution
• Difficult to replace “air barrier”
• Pressurization reduction complex &
controversial
• Controlling humidification best
approach
– Owner pushback--concerned about
occupant complaints
– Wanted 20% RH min as goal
• To test efficacy, 69 wireless data-
loggers installed
56

57. Wireless
Dataloggers
• Occupied Spaces
• Soffits & Concealed Spaces
• HVAC Ductwork
• Outdoor Air
• 15-year Battery Life
57

58. Controlling RH Was Successful
58

59. RH @ 10% Was Acceptable
• No occupant
complaints of dry
conditions during
humidifier
off/lowest setting
periods
• Amount of time
RH was below
20% was minimal
59

60. Modifications
• Placement of Humidifier RH sensors
• Winter time RH at 20% to 25%
• Preventing RH >35%.
• Training
• Monitor data-loggers
60

61. Conclusions
• Condensation did not reoccur by modifying one of the three
issues
• Occupant comfort maintained
• Medical facility contains many complex factors found in high
performance buildings
– Added humidification
– Designed pressurization
– Assumed tight envelope
• Problem avoidance during design phase is best approach:
– Peer review envelope & HVAC & interaction
– Better selection, specification, and detailing of air barrier
61

62. Section 4: Predictability of Moisture
Control & Building Air Tightness

63. Section 4: Predictability of Moisture Control &
Building Air Tightness
• Predictable Elements of Air Barrier Design in High
Performance Buildings
– Drivers + Complexity = Increased Risk
– Failures and air leakage occur at intersections of scope of work
– Don’t overlook the obvious – HVAC openings in the building envelope
– Focus on the requirement that air barriers must be continuous. In
design and installation
• Reduce the number of joints and seams. What type(s) of façade
system(s) provide that?

64. Section 4: Predictability of Moisture Control &
Building Air Tightness
Predictable Elements of Air Barrier Design in High Performance
Buildings
Mid Rise SE US Building
• Two Façade Systems
– Multi-Story Curtainwall
• Atrium Section
– Floor to Floor Window Wall
• Offices

65. Section 4: Predictability of Moisture Control &
Building Air Tightness
Predictable Elements of Air Barrier Design in High
Performance Buildings
Rate Elements of HBB Façade Design in Order of
Importance for Moisture Control and Air Tightness
• Complexity
• Number of Joints/Seams
• Anchoring System
• Perimeter Flashing System
• Roof Wall Intersections (Other Intersections of Scope of Work)
• Aesthetics
• Flexibility
• Cost
• Speed
• Ventilation

66. Section 4: Predictability of Moisture Control &
Building Air Tightness
The Importance of Moisture Control While Achieving
Air Tightness
• Component of Building Performance
– Along with IAQ, HVAC Performance
• High Performance Building Design is Driving
Innovation, Complexity and Risk
– Defect claims

67. Section 4: Predictability of Moisture Control &
Building Air Tightness
• Main Categories to Control Moisture/Condensation and
Conditions Conducive to Mold Growth
– Reduce the driving mechanisms that cause infiltration and localized
depressurization
• Reduce the quantity of mechanical exhaust (Avoid Heat Recovery
Wheels in Warm, Humid Climates – Pressure Neutrality)
• Locate HVAC equipment away from perimeter walls and walls
that separate conditioned from non conditioned space/outdoors
• Minimize mechanical openings in the façade
• Seal openings air tight (Note: Fire stop may not be an air barrier)

68. Section 4: Predictability of Moisture Control &
Building Air Tightness
• Main Categories to Control Moisture/Condensation and
Conditions Conducive to Mold Growth
– Reduce the driving mechanisms that cause infiltration and
localized depressurization(Continued)
• Maintain building positive pressure with cooled dehumidified air
during occupied and non-occupied schedules (Note: OA dewpoints
are highest at night/early morning)
• Specify low leakage dampers
• Reduce openings in ceilings between conditioned and semi-
conditioned or non conditioned spaces

69. Section 4: Predictability of Moisture Control &
Building Air Tightness
• Main Categories to Control
Moisture/Condensation and Conditions
Conducive to Mold Growth
– Provide Non-Continuous Exhaust Whenever
Possible
–Size HVAC Equipment Effectively for Cooling and
Dehumidification

70. Section 4: Predictability of Moisture Control &
Building Air Tightness
• Moisture Control & Air Tightness
–Industry Direction Continues to Be Focused On
• Air Tightness, the number
• Innovation (aka complexity)
• Note: Failures and air leakage occur at intersections
of scope of work
–Predictable with less joints and openings to seal,
greater continuous and uninterrupted air barrier
systems, reduction in drivers, addition of QA

71. Conclusions
• Non-Consensus Still Exists
• Moisture control in high performance buildings is predictable and
achievable
• Air tightness to minimize moisture related problems is predictable
and attainable
• Designers top 5 list
– Validate continuous air barriers by applying pen test to details.
Instinctively know the difference between air barriers and vapor retarders
and when to specify them
– Accept that you may encounter air tightness codes and standards that are
in conflict. Focus on aspects that achieve moisture control
– Focus on reducing/eliminating mechanical depressurization. Beware of the
impacts of heat recovery units on pressurization and dehumidification
control
71

72. Conclusions
• Designers top 5 list (cont)
– Realize that failures most often occur
at intersections of SOW.…..Detail,
detail, detail. Air tightness and
moisture control are achieved through
interdisciplinary work. Avoid working
in silos.
– Manage your risk. Budget for peer
reviews and onsite services. Realize
that innovation = complexity = more
risk in achieving air tightness and
moisture control
72

73. Conclusions
• Contractors top 5 list
– Perform your own due diligence. Evaluate the impacts of sustainability
ordinances in the bidding phase. Realize that not achieving an air tightness
standard may not mean the project is conducive to moisture control problems
– Obtain the services of an independent moisture consultant with envelope and
HVAC expertise who can evaluate these interdisciplinary risks.
– Perform mock ups whenever possible. Increase your quality control. Realize
that failures most often occur at intersections of scopes of work.
– Perform air tightness testing early and often. Budget for hold points.
– Focus on reducing/eliminating mechanical depressurization. Beware of the
impacts of heat recovery units on pressurization and dehumidification control.
73

74. Contact Information
Richard Scott, AIA, NCARB
Senior Forensic Architect/Vice-President
Liberty Building Forensics Group, Gainesville, Florida
352.219.3577
r.scott@libertybuilding.com
Donald B. Snell, P.E., CMC, CIEC
Senior Forensic Engineer/Vice-President
Liberty Building Forensics Group, Zellwood, Florida
407.463.0068
d.snell@libertybuilding.com