The Role of Air Barriers and Continuous Insulation in an Age of Green Construction
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The role of air barriers and continuous insulation is multi-faceted and increasingly important in an age of green construction. Air/moisture barriers and continuous insulation are now mainstream building systems that address the demands of more stringent building codes.
To meet current building code requirements, air barriers must be properly installed to create a continuous building envelope which severely inhibits air and moisture migration. Ideally, compliant moisture barriers will seal around the fasteners.
The adverse effects of non-airtight construction are well-known:
- Unwanted air migration which increases energy costs
- Reduced R-value of moisture-laden insulation
- Increased moisture intrusion via capillarity
- Potential development of toxic mold, odor-producing mildew, wood rot and corrosion
- Premature failure of building components
When insulation gets wet, it quickly loses its ability to resist thermal flow, and property owners do not achieve expected energy savings. Mold remediation and the replacement of rotted wood or corroded metal is expensive and time-consuming. In a variety of ways, a non-airtight structure fails as a green building.
Common air barriers include:
- Rigid foam sheathing made airtight through the proper application of durable tapes
- Elastomeric materials which are fluid or trowel-applied
- Mechanically fastened housewraps
- Self-adhering sheet products, including peel-and-stick membranes like DELTA®-VENT SA
The Air Barrier Association of America (ABAA) has established master specifications for the various types of air barriers. Successful air barriers will:
- Reduce required HVAC system size while improving efficiency
- Properly manage air pressure relationships
- Allow water vapor to escape from wall cavities
- Increase occupant comfort through reduced drafts
- Enhance indoor air quality
High-performing air barriers allow for reductions in the size of heating and cooling units, thereby offsetting initial capital costs, at least to a degree. By properly controlling air pressure inside the wall system, it is possible to reduce moisture intrusion that passes through via infiltrating air.
This final point should not be understated, because infiltrating air flowing unimpeded through a wall system also allows allergens, pollutants and bacteria to invade, potentially compromising the health of building occupants. While air that moves uncontrolled through walls does lead to air exchanges in a structure, this is not fresh air.
Continuous insulation blankets a structure to maximize energy-efficiency. It is an essential component of highly efficient green building best practices. In fact, continuous insulation is now required in jurisdictions following ASHRAE 90.1-2007 and IECC 2009.
Continuous insulation is the obvious solution to the unwanted heat loss or gain associated with thermal bridging. Thermal shorts exist where unwanted temperature equalization occurs along a path of least resistance, typically wood studs or steel framing. A layer of continuous insulation across wall components and cavities attenuates the atmosphere’s ongoing effort to equalize these temperature differences between interior and exterior areas.
Common types of continuous insulation include rigid foam sheathing like XPS, EPS, rockwool, fiberglass, and Polyiso, as well as closed-cell spray foam. The quest for truly continuous rigid foam insulation is oftentimes elusive. Although foam sheathing addresses the problem of thermal bridging, effectively taping to fully eliminate air and moisture intrusion is a challenge. For example, overlapping is usually difficult due to the thickness of the panels, so horizontal tape runs are sometimes vulnerable to moisture intrusion.
Also, the expansion and contraction of such panels may compromise the integrity of the taping over time. For example, a 48×96” XPS panel may expand or contract as much as 1.9 inches. Other rigid structural panels require a quarter-inch gap to cope with inherent dimensional instability. There are now special tapes available that can manage this movement. Because these special tapes may not be used by the contractor, some architects and designers specify the use of an air/moisture barrier in conjunction with foam sheathing to ensure airtightness.
DELTA®-VENT SA, a high-performing, vapor permeable air/moisture barrier, is one of the DELTA® products from Dörken. The 3-layer construction of the membrane is designed to allow for the natural expansion and contraction of a structure, while maintaining its integrity to support the continuous protection of the wall system. The DELTA® line also includes ventilated rainscreen systems and below-grade moisture protection and drainage.
Green Practice & Products
Energy efficiency is just one component of green building. Using sustainable products is another. In addition to meeting and exceeding stringent codes, DELTA® products are non-toxic, non-polluting, 100% recyclable and function for a lifetime. Dörken also utilizes recyclable and minimal packaging for all their products as part of their commitment to the environment.
Dörken delivers innovative, high-performance air and moisture barriers for commercial and residential construction sold under the DELTA® brand name. A North American manufacturer based out of Beamsville, Ontario, Dörken Products, Inc. is a subsidiary of Ewald Dörken AG, a leading European developer and manufacturer of waterproofing and drainage products sold worldwide. Dörken is known for delivering premium products while providing educational programs and full technical support. For more information, call 1-888-4DELTA4 (433-5824) or visit www.dorken.com.