Proactively adopting these new methods helps builders and contractors differentiate themselves from competitors and stay ahead of increasingly stringent code changes.
A tight building envelope is recognized for its energy efficiency contributions. There are increasingly stringent regulations and code specifications for tighter envelopes due to energy wasted through air leakage.
While building performance homes requires some change, high quality mechanicals, smart control strategies and efficient lighting are all key methodologies. But energy efficiency really starts with the building envelope. Creating a tight envelope requires a system-wide approach and the integration of air tightness, R value, construction types, aesthetics, total U value and continuous insulation as well.
In addition to the benefit of providing greater energy efficiency, a tight building envelope also produces increased comfort for homeowners, better indoor air quality, and improved moisture management.
According to the Department of Energy, uncontrolled air leakage can account for as much as 30 to 50 percent of a home’s heating and cooling costs. The reason is simple: every bit of outside air that enters the home through air infiltration must then be heated, cooled and/or dehumidified to get back to a thermostat’s set point.
With tight buildings, ventilation must be controlled mechanically. Rather than allowing “fresh air” to enter randomly whenever the wind blows through whatever cracks and gaps are available, air is brought in from outside, passed through a filter, pre-conditioned, and then delivered anywhere within the building.
A tight building envelope also reduces allergens by keeping out pollen and sealing occupied spaces off from areas like garages, where people can be exposed to fumes from cars, paints or household cleaners. And, managing moisture is the key to mitigating mold concerns. Air leakage is a very fast process and presents a high potential for condensation, mold and rot.
The benefits of a tight building envelope are clear, and building tight buildings is about more than just using air barrier materials. It’s the transitions, connections and penetrations that determine air tightness. The ceiling and attic, parapet wall transition, cantilevered floor, crawl space, rim and band joists, windows and doors are what most often leak.
Regardless of material selection, there are some concepts to keep in mind:
The air barrier should be continuous around the entire building envelope.
The air barrier material selection needs to make sense for the cladding type, drainage plane requirements, substrate and climate.
Transition membranes and flashings are critical to performance.
Air barrier transitions need to be detailed in the drawings per manufacturer’s recommendations.
Workmanship and attention to detail are key for any air barrier installation, but some systems are more robust than others.
