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HOW TO ACHIEVE A TIGHT BUILDING ENVELOPE WHAT LIES BENEATH. Facility design and building materials are important components of achieving a tight, effi cient building envelope. Gaps caused by inadequate or incorrect con- struction can result in air leakage, leading to increased HVAC costs, comfort and moisture problems, the infi ltration of pollutants, reduced fi re safety, and potential access for rodents and insects. What you see on the outside — windows, doors, and exterior walls — can contribute to air leakage, but the greatest losses can happen in hidden cracks and holes, which can cause air exchange between the interior and the outdoors. Continuity of transitions. There are a number of areas where building parts meet: founda- tion to wall, wall to window, wall to roof, wall to wall. More specifi c examples include where a curtainwall attaches to a precast wall or a masonry wall joins a stucco wall. It's important that all of these transition spots are well joined. "If you don't get it right, you have a weak link, and you'll get heat escaping and cold air entering," says Kikta. Compatibility of materials. There are a number of air barrier products that can be used to create a tight envelope at transi- tion points, including sheet membranes, silicone sheets, sealants, and spray foams. However, certain materials, when used together, cause a degradation of one of the materials, resulting in a loss of tightness. So the compatibility of different materials must be taken into consideration before construction begins. "It is a straightfor- ward process for architects and contrac- tors to check with manufacturers about compatibility," says Jonathan Baron, AIA, LEED-AP, an associate with Shepley Bulfi nch, a Boston-based architecture and design fi rm with offi ces in Phoenix and San Francisco. "But it is a step that is easily overlooked." Mockups. Constructing an eight- to 10-ft. section of the facility's wall components on the building site and checking the mockups with the contractor to validate that every- thing is being done right goes a long way towards ensuring a tight building envelope. Additionally, a sophisticated owner will hire an outside group who will determine what testing will be done on mockups, says Baron, who co-chairs the Building Enclosure Council of the Boston Society 46 COLLEGE PLANNING & MANAGEMENT / JUNE 2012 of Architects. This is especially critical because, once a building is complete, it's costly to address challenges. Building commissioning. This systematic and documented process, which primarily ensures the owner's operational needs are met and building systems perform effi - ciently, is now standard practice. "There is a cost to it," Baron admits, "but it shouldn't be substantial compared to long-term savings. Still, when you're looking at fi rst costs, it can be a diffi cult pill to swallow." Doing It Better Today The experts note three industry trends that also can help achieve a tight building envelope. The fi rst is an air and vapor barrier transition assembly. Building connec- tions must be compatible and sequenced WWW.PLANNING4EDUCATION.COM