The Four Barriers Not Independent. Avoiding Pitfalls with Air Barriers. Summary: Vapor Retarder vs Air Barrier. Summary: Vapor Retarder vs Air Barrier

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1 The Four Barriers Not Independent DESIGN INVESTIGATE REHABILITATE Avoiding Pitfalls with Air Barriers Presented by: Vince Cammalleri, AIA Senior Principal Simpson Gumpertz & Heger Inc. Evaluation Criteria: Reliability Durability Suitability Constructability + CONTINUITY BARRIER 1: Waterproofing BARRIER 2: Insulation BARRIER 3: Vapor Retarder BARRIER 4: Air Barrier Rainwater/Groundwater Control Condensation Control & Energy Consumption BUILDING SCIENCE 12 April Summary: Vapor Retarder vs Air Barrier Summary: Vapor Retarder vs Air Barrier Vapor Retarder Continuity does not need to be perfect Location set by particulars of climate and material properties Strength is not an issue Air Barrier Must be continuous; perfect barrier seals Location set for ease of detailing Vapor permeance not important Must resist positive and negative pressure Need both a vapor retarder and an air barrier system in the building envelope to control vapor diffusion and air leakage. These two systems can sometimes be combined into one. Controlling Vapor Migration Controlling Vapor Migration Exterior Interior Exterior Interior VAPOR RETARDER (on warm side) AIR BARRIER (on interior) AIR BARRIER (on interior) VAPOR RETARDER (on warm side) 1

2 Controlling Vapor Migration Insulation Inboard of Sheathing (hot climates) Exterior Interior AIR BARRIER and VAPOR RETARDER (on exterior) Controlling Vapor Migration Controlling Vapor Migration Exterior Split Insulation (moderate climates) Interior Exterior Insulation Outboard of Sheathing (colder climates) Interior AIR BARRIER and VAPOR RETARDER (on exterior) AIR BARRIER and VAPOR RETARDER (on exterior) Common Barrier Pitfalls Common Barrier Pitfalls Misunderstanding of Concepts/Dynamic Performance Inappropriate Material Selection Lack of Design/Detailing Direction Provide sufficient details Design system that is constructible Ensure that air barrier is continuous General - plan and section Major intersections roof/wall, floor/wall, foundation, etc. Between different wall systems, window/wall interfaces At seams within barrier material/assembly At penetrations (electrical, plumbing, HVAC, etc.) Insufficient Design Redundancy Control source Provide continuous/reliable/constructible barrier Select durable materials Allow for evacuation of moisture Lack of QA/QC and Construction Monitoring Pre-construction/sequencing meetings Value engineering set priorities straight Mock-ups Field review 2

3 Air Flow Driving Pressure Differential is a Combination of: Wind Pressure Stack Effect Mechanical Systems Wind Effect WIND DIRECTION Stack Effect Mechanical Systems Neutral Pressure Level Mechanical Systems Mechanical Systems 3

4 Air Flow Driving Pressure Differential is a Combination of: Wind Pressure Stack Effect Mechanical Systems Air Flow Between Adjacent Interior Spaces Climate-controlled spaces Clean air spaces AIR BARRIER DESIGNATION Understanding Dynamics of Enclosure/HVAC Interaction. Interstitial Air Flows Within Walls and Roofs Metal Roof Supply Air Ducts Polyethylene Vapor Retarder ROOF SECTION ROOF SECTION 4

5 ROOF SECTION Roof - Clerestory LCC over roofing paper, roofing felt, wood sheathing (OSB) and rigid insulation. Beneath Clerestory Roofing Wet roofing paper and roofing felt Apparent Mold Growth Friable OSB INTERIOR AIR BARRIERS Controlling air flow between adjacent spaces. LCC attachment compromised 5

6 Condensation in Adjacent Spaces Natatorium Storage room Interior Air Barriers Interior Air Barriers Air Flow - Infiltration in Cooling Climates AIR BARRIERS AND INTERIOR AIR PRESSURES Controlling air flow within wall systems. CONDENSATION (within cold partition) Direction of Air Flow 6

7 Source: CMHC 2007 Simpson Gumpertz & Heger Inc. Proprietary and Confidential AIR BARRIERS AND INSULATION Controlling air flow between cold wall and insulation systems. Location of Air Barrier Location of Air Barrier Hole AIR BARRIER (on interior) AIR BARRIER (on exterior) Hole Direction of Air Flow Direction of Air Flow 7

8 Air Flow - Exfiltration at Precast Concrete CONDENSATION (at cold surface) Hole AIR PATH Direction of Air Flow 8

9 Air Flow - Exfiltration at Precast Concrete CONDENSATION (at cold surface) Hole AIR PATH Direction of Air Flow 2007 Simpson Gumpertz & Heger Inc. Proprietary and Confidential 9

10 AIR BARRIER MATERIALS Understanding material and product uses and limitations. Housewraps Liquid-Applied Air Barriers 10

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13 Spray-Applied Foams 13

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15 Self-Adhering Rubberized Asphalt Membranes 15

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18 AIR BARRIER DETAILING 18

19 Construction Geometries Cold cavity Gypsum wallboard bulkhead w/ batt insulation Rigid insulation Open gap between penetrating steel

20 Construction Geometries Open joint between steel members

21 Gypsum wallboard bulkhead w/ batt insulation Cold cavity DESIGN REDUNDANCY Rigid insulation 21

22 5/8 inch foil-faced gypsum board ROOF/WALL INTERSECTION 22

23 MOCKS UPS, TESTING AND FIELD MONITORING Field Quality Assurance Verification and Testing Infrared (IR) Thermography Prior to Repairs Field Quality Assurance Verification and Testing IR Thermography After Repairs

24 Field Quality Assurance Verification and Testing ASTM E779 Standard Test Method for Determining Air Leakage Rate by Fan Pressurization Quantitative testing Zone balancing based on building layout Air infiltration through envelope Quantitative identification of performance Does not identify breaches Field Quality Assurance Verification and Testing Quantitative testing Field Quality Assurance Verification and Testing ASTM E1186 Standard Practices for Air Leakage Site Detection in Building Envelopes and Air Barrier Systems Qualitative Testing Tracer smoke Smoke generator Pressurization versus depressurization Visual identification to determine breaches Infrared Thermography Shows surface temperature of cladding Indicates breach in air barrier or breach in thermal barrier Sample opening verification required Field Quality Assurance Verification and Testing Qualitative testing Field Quality Assurance - Construction Construction Mock-ups PROVIDE PICTURE OF TESTING MOCK-UP

25 Mock-up Testing Benefits: Gathers design-construction team well in advance of construction Can highlight some performance deficiencies. Can bring other important issues to the surface i.e., coordination of trades, sequencing, material lead time, assembly clearance and tolerance. Cautions: No guarantee of field performance - due to lack of production workmanship, weathering, and use of short term fixes. Successful tests can provide false sense of security and relaxation in monitoring and testing the actual installation. Bottom Line: Preproduction testing is often useful, but it does not supplant proper design and careful monitoring of installation. CONTINUITY Metal sill flashing with upturned edges and soldered end dams; seal upturned edge to window frame. Self-adhering rubberized asphalt air barrier/vapor retarder membrane SILL DETAL Window Sill Detail No seal between window and flashing Self-adhering rubberized asphalt air barrier/vapor retarder membrane Sticky side SILL DETAL 25

26 DESIGN INVESTIGATE REHABILITATE Thank You Vince Cammalleri, AIA