LEED Certification and Air Infiltration
Leadership in Energy and Environmental Design (LEED) certification is an independent verification method that recognizes green building performance. LEED certified buildings are generally assumed to be more energy-efficient than standard structures. LEED® certification can enhance a building’s value, generate higher commercial lease rates and reduce utility costs.
By 2018, it is estimated that LEED-certified buildings will contribute almost $30 billion to U.S. GDP. The program’s global impact is also significant. There are now more than 79,000 LEED-certified projects in 160 countries. The continuing need for green building design and construction is significant. The U.S. Green Building Council estimates that 73 percent of all electricity consumption occurs in buildings, and they are responsible for 38 percent of all CO2 emissions in the country.
LEED-certified buildings often use 20 to 30 percent less energy, thereby reducing carbon emissions as well. For example, LEED Gold commercial buildings in the GSA portfolio consume approximately 25 percent less energy and generate 34 percent lower greenhouse gas emissions than structures that are not certified.
Airtight Structures
LEED certification is typically dependent on, among other things, airtight construction. Therefore, a high performance air and moisture barrier with superior UV stability, tear-resistance and surfactant resistance will better assist architects and builders in achieving coveted LEED certification.
The use of a high-performing air barrier is of utmost importance in accumulating LEED points. Here are some key considerations:
UV resistance – Common building wrap is often vulnerable to the deleterious effects of ultraviolet light. Some materials begin to deteriorate after a relatively short period of UV exposure, particularly in sunnier parts of the country. Southern areas feature a higher sun angle which can also intensify UV light.
Tear resistance – A rugged air and moisture barrier that’s resistant to tearing is crucial to airtight performance. Even small tears incurred during the construction process can quickly compromise resistance to air infiltration. A high-quality air barrier will resist tearing, both from high winds and from the rigors of the construction site.
Surfactant resistance – Finally, some compounds found in cladding materials like oils, tannins and turpentine can compromise the waterproof nature of common building wraps by altering their pore structure. When this occurs, the material fails to protect the sheathing from high winds, heavy rain and consequent water damage.
A properly installed, high-performance air and moisture barrier minimizes unwanted air infiltration. It is often complemented by a robust ventilation system that brings routinely fresh air to the building’s occupants. Successful blower tests depend on the retention of the integrity of the WRB during construction.
Rate of Permeance
The ability of an air barrier to transfer water vapor, expressed as the permeance, is very important. The permeance is the number of grains of water vapor that pass through a square foot of a material every hour. The higher the “perm rating,” the greater the permeability of the material. Although current building codes often require a building wrap rated at five perms, a high performance air and moisture barrier may offer a high 50 perm rating.
Air Infiltration Challenges
The importance of an air barrier’s resistance to air infiltration should not be understated. It is estimated that a typical 2,500 square-foot home has approximately a half-mile of gaps and cracks and crevices that are vulnerable to the impact of both wind and rain driven by high winds. Now expand those square feet to the size of a typical commercial building and think about how many miles of gaps can occur.
To fully realize the benefit of a high-quality air and moisture barrier, it is important to properly deal with decks, band joists and window and door flashing to retain the overall integrity of the air barrier. Ultimately, poorly installed or lower quality barriers increase drafts, decrease comfort and increase energy waste.
LEED certification is highly dependent on preventing these things from happening. In fact, the proper use of a high-quality WRB is one of the easier ways to accumulate LEED certification points in both the commercial and residential categories. The LEED certification system of the U.S. Green Building Council will only grow more important over time. Commercial developers and homeowners will increasingly value builders that use sustainable building techniques and architects that design highly sustainable structures.
Cosella Dörken’s DELTA®-VENT SA is a high performance air and moisture barrier that assists those looking to get LEED points. It is a vapor permeable (50 perms) WRB with a high degree of strength and tear resistance. Knowing that the key to good air sealing is in the system and its accessories for easy installation, Dörken provides many tested details that help ensure constructable success. Simply having an air tight membrane is no guarantee of air tightness in a system. Because DELTA®-VENT SA is fully adhered, it is much easier to install correctly to insure an air and moisture tight building.
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.
