Home achieves an EnerGuide rating of ‘0’ by generating as much energy as it consumes
June 15, 2017 by John Bleasby
Falcon Heights Contracting Ltd. owner Dave Mackenzie, has been a BuiltGreen® certified home-builder for about seven years. However, his latest custom project in Victoria, B.C. took his desire to build in a sustainable manner to the highest level. On June 5, 2017 the Canadian Home Builders’ Association (CHBA) acknowledged his efforts by recognizing the house as the first qualified under its Net Zero Home Labeling Program launched in May.
Net Zero was the next logical step for Mackenzie’s company
BuiltGreen® Platinum, the program’s highest level, has been Mackenzie’s company benchmark for a while now, so aiming for Net Zero Energy (NZE) only seemed natural. Mackenzie returned from a three-day NZE training course in Kelowna, B.C., with the goal of taking his clients for this project to the next level. “Energy conservation was really important to the homeowners,” he told Canadian Contractor. “I was able to convince them to step it up to see if we could meet Net Zero.”
The location posed big NZE challenges
It wasn’t an easy undertaking, however. The site was a stunning waterfront setting, and huge amounts of glass were key elements of the design. “Obviously being a waterfront custom home, the view and the large amounts of glazing trumped everything. You can’t tell clients with a multi-million piece of property that they can’t look out over the water!”
“We had to model the house through the EnerGuide software simulations 13 times to get it to meet Net Zero performance,” Mackenzie says. However, he wanted to avoid throwing increasing amounts of PV arrays onto the roof in order to get there. “You can always get to Net Zero by throwing buckets of money at it like that, but it was our goal not to exceed 10 or 11 kilowatts. We were running out of roof area and it was getting to be cost-prohibitive.”
A total thermal break envelope
To reach the Net Zero target with the amount of glazing in the design, Mackenzie decided to wrap all the exterior walls under the final cladding in 2-inch semi-rigid Roxul insulation. He prefers semi-rigid insulation over rigid polystyrene for breathability reasons. “The nice thing is that you’re getting breathing between the air barrier and the cladding. Moisture doesn’t get trapped and rot out the walls.”
Using traditional wood frame construction in combination with the exterior thermal-break insulation layer and two-pound closed cell foam applied on all interior wall and roof surfaces, Mackenzie was finally able to achieve the Net Zero targets. “We were getting nearly R45 in our walls and R65 in our ceilings,” says Mackenzie. In terms of air-tightness, the home was measured at 0.7 air changes per hour, versus code-built homes that are typically rated at four to five air changes per hour.
Addressing the challenge posed by huge windows
The massive expanses of glass were the final piece of the puzzle for achieving Net Zero. “We used locally-supplied, Low-E triple glazing in high performance PVC framing,” Mackenzie explains. “Going to triple glazing only added 12 per cent to our window cost, so that was a nice surprise.” Low-E glass has a transparent coating thinner than a human hair that can reflect both long-wave infrared energy (or heat) and significant amounts of short-wave solar infrared energy.
The solar heating coefficient was also very low, far superior to standard windows. “There’s really no extra cost going to a low solar heat coefficient; it’s just something you have to be aware of when you’re ordering the glass,” Mackenzie says. “And the colour didn’t change either. In the old days of high performance solar heating coefficients you would get a very green glass. However, we were very pleased to see that the coating didn’t really change the colour of our glass.”
That 12 per cent figure is also the amount Mackenzie estimates to be the overall added cost of bringing this home to the Net Zero level versus his standard BuiltGreen® Platinum approach, after giving consideration to all the individual elements like windows, doors, insulation, and thermal breaks.
CHBA hopes to build on their labeling program
The CHBA hopes other builders will follow MacKenzie’s lead. Their Net Zero Home Labeling Program provides the industry and consumers with a clearly defined and rigorous two-tiered technical requirement that recognizes Net Zero and Net Zero Ready Homes, and identifies the builders and renovators who provide them.
“CHBA supports leading-edge innovation in the residential construction industry with the goal of having those innovations as a voluntary and affordable choice for consumers,” said Kevin Lee, CEO. “The Net Zero Home Label will help to meet the energy efficient housing aspirations of Canadians, while strengthening Canadian industry leadership in high performance housing.”
Read Canadian Contractor’s ongoing new series, “The Road to NZE”
Part One: How whole-house energy ratings are shaping the homes of the future
Part Two: Defeating thermal bridges
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