“An ineffectively designed duct system is a big problem,” Locke says. “People just slap up the system without checking how much air it throws or how many cubic feet per minute the system handles.”
To combat this lack of precision, consultants say, builders should perform energy modeling on their HVAC systems and properly size their units. Oversized units don't stay on long enough, and the bursts of warm or cold air can deceive a thermostat into shutting off the system before the house is adequately conditioned. An adequately sized unit also improves the humidity levels in the home and costs significantly less.
Sealed ducts, meanwhile, improve the indoor air quality and comfort of the home, lower energy bills, and allow builders to lower equipment costs. “We seal our ducts and do duct-blast testing to ensure proper operation,” says Sessions.
Miller says his company installs ductwork in conditioned spaces only. “Leaky return ducts can draw air out of unconditioned spaces that is hotter or colder than the return air, thus increasing loads on heating and cooling systems,” the company says. Moreover, return ducts in attics, unfinished basements, crawl spaces, and garages can also draw pollutants and contaminate indoor air.
“We use an energy recovery ventilation system,” Briley notes. “It senses carbon dioxide and humidity and activates [itself in response]. It exhausts stale air and tempers and introduces warm, humidified air to the house. You essentially control the leakiness of the house.”BREATHE EASY
Now that your shell is tight and you have designed an efficient HVAC system, the last thing you want to do is pollute your interior air with off-gassing building products.
Thankfully, manufacturers have made it easier for builders to avoid toxin-laden products. Low volatile organic compound (VOC) paints, stains, and finishes are widely available from such companies as Sherwin-Williams, Benjamin Moore, and Rodda Paint. Columbia Forest Products offers formaldehyde-free veneer paneling for cabinetry and furniture, and Johns Manville now makes a formaldehyde-free insulation. A variety of materials—bamboo from Teragren, cork from Expanko, linoleum from Forbo—also makes it easy to install a durable, sustainable floor.
Making sure the interior air is free of volatile organic compounds is part of a larger, important effort to make sure high-performance homes are healthy and safe for homeowners, says Jay Hall, director of research at Building Knowledge. The company, a Minneapolis-based building science consulting firm, works with builders to get them up to speed with energy-efficient techniques.
GREENHOUSE RULES: Dispelling the myth that a high-performance home is expensive, architect Chris Briley and Green Quality Homes designed and built this 2,200-square-foot spec home for about $350,000. The home incorporates insulated concrete form foundation walls, cellulose insulation, in-floor radiant heating, gasketed electrical outlets, bamboo floors, dual flush toilets, countertops and vanities made from recycled paper, and nontoxic adhesives, coatings, and products.
“We figure out where the builder is and help them figure out the logical next step to address issues in an efficient way,” Hall explains. “It's a big leap to get there all at once, because there are a lot of [points] to work out, which is why we promote an incremental approach.” Part of that incremental approach includes stressing health and safety issues such as indoor air quality, combustion gas, and radon. The company has a list of priority areas it addresses when working with builders.
After conducting a baseline assessment, Building Knowledge's priorities for the builder include combustion safety, water management, the thermal shell, and air tightness. Then they move on to crawl-space design improvements, HVAC redesign, increased duct tightness and relocation, and ventilation issues.BETTER ALL AROUND
A high-performance home will be safer to live in and will have lower utility bills than a typical home, but it will also be a better house all around, says Mike Kerwin, a partner with Lorax Development, a six-year-old San Francisco–based company that builds green houses. “To me, high performance relates to energy efficiency and quality of materials, and how a home will perform over time,” he says. “For the home buyer, this means a certain peace of mind, fewer maintenance costs, and added value down the road.”
All of these recommendations merely scratch the surface of the research conducted by building scientists, green building programs, and other experts, and they serve purely as a starting point for building high-performance homes. For example, a high-performance home in a very cold climate will likely be built differently from one in a hot and humid area, so builders should take regional conditions into consideration and build accordingly.
Experts agree, however, on one step that all builders should follow, no matter what high-performance construction methods they use or where they build: Obtain third-party certification. Prescriptive methods say one thing about how a product will perform in the field, but the only way to know for sure whether something was installed correctly to achieve high performance is by having a third party examine it. It is not as difficult as it was in years past to have your homes certified by a third party. All across the nation, trained consultants and engineers have been approved to test homes to make sure they are performing as efficiently as they should.
Indeed, installation is where the rubber meets the road for the testers, Locke says. “Installation isn't always done correctly, so most homes aren't high performance,” he says. “There's a cascade effect [contributing to subpar performance] because people don't look at how these things work together.”