SpecTips - Reducing Air Intrusion with Air and Vapor Barriers
VapAirSeal MD –A Cost-Effective Way to Beat Back Air Intrusion on Metal Decks
Air intrusion has been an increasingly frequent topic of discussion in the roofing industry over the last decade.
Air intrusion is when the conditioned interior air moves into the roofing system without escaping the building envelope. This is particularly prominent with mechanically fastened roof systems because the sheet is only attached at the seams. The conditioned interior air enters the roof system through insulation gaps, penetration gaps,and through fastener penetrations. The air is then exposed to exterior conditions when it comes into contact with the underside of the roof membrane.
These dynamics can cause condensation issues, which will impact the longevity of the roof system and may lead to mold problems. In addition, when the air encounters the exterior conditions and then circulates back into the conditioned space,it will increase the workload of the HVAC system and reduce the building’s overall energy efficiency.
IECC has recognized this issue and requires mechanically fastened roof systems to have an air and vapor barrier to address this concern (IECC 2012 -C402.5.1.1). The IECC states that an assembly can have no more than 0.04 cfm/ft2of air leakage.
Carlisle’s VapAir Seal™MD is a cost-effective way to address air intrusion and meet energy code requirements when installed on metal deck roofing applications.
VapAir Seal MD features a tough, puncture-resistant,aluminum-coated poly film laminated to11-13 mils of SBS adhesive, which provides a strong bond to the metal deck. The thin amount of adhesive allows VapAir Seal MD to be applied directly to the metal deck without a thermal barrier (such as a gypsum board) and still meet FM 4470 Class 1 and UL 1256 internal fire ratings.
VapAir Seal MD self-seals around mechanical fasteners that penetrate through it and remains in place. With the equivalent of 1 fastener per square foot, VapAir Seal MD achieves an air leakage rating of 0.005cfm per square foot when tested to ASTM E2178, which is well below the IECC standard of 0.04 cfm per square foot for an assembly.
By eliminating the need for a thermal barrier and not requiring a primer prior to installation, the installed price for a VapAir Seal MD system is around one third to one half the cost of installing a traditional air and vapor barrier over a metal deck.
Spec Tip
In 3-Part Specifications –Part 2 “Products”,include the following air and vapor barrier criteria when a metal deck is used:
For more information view the Air and Vapor Barrier Field Guide here.
Air intrusion has been an increasingly frequent topic of discussion in the roofing industry over the last decade.
Air intrusion is when the conditioned interior air moves into the roofing system without escaping the building envelope. This is particularly prominent with mechanically fastened roof systems because the sheet is only attached at the seams. The conditioned interior air enters the roof system through insulation gaps, penetration gaps,and through fastener penetrations. The air is then exposed to exterior conditions when it comes into contact with the underside of the roof membrane.
These dynamics can cause condensation issues, which will impact the longevity of the roof system and may lead to mold problems. In addition, when the air encounters the exterior conditions and then circulates back into the conditioned space,it will increase the workload of the HVAC system and reduce the building’s overall energy efficiency.
IECC has recognized this issue and requires mechanically fastened roof systems to have an air and vapor barrier to address this concern (IECC 2012 -C402.5.1.1). The IECC states that an assembly can have no more than 0.04 cfm/ft2of air leakage.
Carlisle’s VapAir Seal™MD is a cost-effective way to address air intrusion and meet energy code requirements when installed on metal deck roofing applications.
VapAir Seal MD features a tough, puncture-resistant,aluminum-coated poly film laminated to11-13 mils of SBS adhesive, which provides a strong bond to the metal deck. The thin amount of adhesive allows VapAir Seal MD to be applied directly to the metal deck without a thermal barrier (such as a gypsum board) and still meet FM 4470 Class 1 and UL 1256 internal fire ratings.
VapAir Seal MD self-seals around mechanical fasteners that penetrate through it and remains in place. With the equivalent of 1 fastener per square foot, VapAir Seal MD achieves an air leakage rating of 0.005cfm per square foot when tested to ASTM E2178, which is well below the IECC standard of 0.04 cfm per square foot for an assembly.
By eliminating the need for a thermal barrier and not requiring a primer prior to installation, the installed price for a VapAir Seal MD system is around one third to one half the cost of installing a traditional air and vapor barrier over a metal deck.
Spec Tip
In 3-Part Specifications –Part 2 “Products”,include the following air and vapor barrier criteria when a metal deck is used:
- The air and vapor barrier shall be adhered directly to the metal deck.
- The air and vapor barrier shall meet UL 1256 and FM 4470 Class 1.
- The air and vapor barrier shall have a reinforced polyfilm.
- The air and vapor barrier shall be tested to ASTM E2178 with 1 fastener per ft2 - max air leakage 0.005 cfm/ft2.
For more information view the Air and Vapor Barrier Field Guide here.
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