By Jenn Danko
When it comes to the buzz surrounding net-zero construction, Derek Satnik sees the practice as a future necessity rather than a fleeting fad. An energy engineer, technical specialist and green energy policy expert, Satnik also serves as managing director of Mindscape Innovations Group, Inc., a nationally awarded energy and environmental consulting firm that specializes in green practices. He works out of Kitchener, Ont., where he says net-zero construction is gaining momentum in niche markets.
"There is certainly a fan-following of aggressive net-zero construction in Canada," says Satnik, a founding member of the Canada Mortgage and Housing Corp (CMHC)'s Net-Zero pilot program, which launched in 2005.
"In basic terms, net-zero buildings produce as much energy as they consume on an annual basis," says David Silburn, research associate, green building technologies, South Alberta Institute of Technology Polytechnic.
But what types of new practices have emerged to make more net-zero buildings possible?
"Believe it or not, most of the best techniques are not new," says Satnik. "The greatest energy sink in the typical home is air leakage—which is energy wasted by heating or cooling the outdoors rather than keeping conditioned air inside the building envelope."
To make homes air-tight, Satnik suggests paying close attention to sealing up a vapour barrier properly, especially around joints, corners, headers, windows and doors, electrical outlet, pot-lights or other ceiling penetrations. Those who truly approach net-zero construction, will use Tuck Tape to seal staples that hold vapour barrier poly to the studs within walls.
In fact, ample insulation is one of the defining traits of an effective, net-zero building.
"The general rule is that more insulation is better," says Satnik, who has seen successful designs include double-stud walls that contain batts, thick foam walls, double studs with cellulose, insulated concrete forms and structurally insulated panels. All of these techniques are acceptable net-zero practices.
But be wary, he adds. Not all insulations are the same, so it's worth understanding their various needs and limitations.
"For example, batts often get squished around electrical outlets and wires in the wall when they should instead be cut to fit, or separated and wrapped in front of and behind wires," he says.
Additionally, better-insulated walls, ceilings, and basements are key to building a net-zero home—especially within the foundation, where the highest amount of heat loss occurs.
"In our Discovery 4 research homes, we've significantly increased the basement insulation, which will save a homeowner a lot of energy," Silburn says. "About 20 percent of heat loss is associated with a basement whereas within an attic, you lose about five percent. Increasing insulation in your attic doesn't get you the same bang for your buck."
Equally as important as insulation are mechanical systems, which must first be sized properly to be successful in net-zero construction. Energy-efficient buildings do not need as much heat and oversized systems will not run as efficiently in an advanced home, Satnik says. Additionally, remember to practice proper installation techniques.
"Duct systems often leak terribly, which makes it difficult to get air through the house to where it's intended to go," he explains. "Rather than using aluminum tape to seal joints, consider using 'nasty goup' to seal them."
He suggests assembling the ducts on the floor and letting them dry fully before hanging.
"The end result is vastly improved over typical ducting installations and the homeowners will feel the performance benefit," Satnik says.
Net-zero building techniques may work well for new construction, but what about retrofits? How can net-zero building practices be applied to older homes?
At SAIT Polytechnic, David Silburn, research associate in green building technologies and his teams have developed a specialized window shutter that also generates heat. This "solar thermal shutter" and other solar thermal panels can be easily fitted to older homes to pre-heat their domestic hot water heaters and help to increase their net-zero capabilities.
For the interior, Derek Satnik, managing director of Mindscape Innovations Group, Inc., recommends using spray foam to insulate looser areas of the home. Contrary to popular belief, not all windows and doors have to be replaced, he says. They do, however, almost always need resealing.
"Leaky windows should be replaced, but efforts should focus on sealing around the window casing and adding weather stripping to doors," he says. "Remember that the cheapest items are often the biggest impact; cutting air leakage means directly eliminating the energy used to heat or cool lost air and always has a bigger impact than upgrading a mechanical system."
Regardless of the level of upgrades involved, both Satnik and Silburn recommend consulting local Canadian incentive programs for guidance on which mechanical upgrades may make the most sense.
Adds Silburn, "Hiring a consultant to provide an energy audit and verify the amount of energy you are actually using will make a big difference in prioritizing insulation, air sealing, and energy efficiency."