Knowing this home is efficient seems to make the view that much better
Saanich project meets the challenge of building net zero
One look at the pictures of Barry and Chris Buchkowsky's view and you know why the couple wanted one side of their house to be windows.
The home is built on Parker Avenue in Saanich, looking east out over Cordova Bay. Even on a cloudy day the scene is stunning.
But in suggesting that the Buchkowsky home be constructed to meet strict net zero technical requirements, builder Dave MacKenzie set himself a challenge.
Net zero homes are at least 50% more efficient than buildings constructed to the BC Building Code and have a renewable energy system that can produce as much energy as the home uses. A key feature of an energy efficient home is a great thermal envelope that reduces the amount of heat either leaving, or coming into, the home. And that's done with good insulation, efficient windows and doors, and by carefully sealing everything to make the home air tight.
Building Net Zero, working with constraints
On the phone from Victoria, where his Falcon Heights Contracting firm is based, MacKenzie explained that one way to achieve a net zero home is to build thick walls with small or even no windows. MacKenzie said that wasn't an option in this case.
"We weren't going to take away that view."
So he decided to use triple-pane windows in the home to allow his clients to enjoy the full view while ensuring that the house would not overheat in the summer sunshine or be uncomfortably cool in the winter months because of its windowed front.
To achieve net zero Mackenzie first started by reducing the heating and cooling requirements of the home by improving envelope's insulation and air tightness. He did that by insulating the walls and ceiling with two inches of semi-rigid insulation on the outside and by supplementing that with spray foam insulation that reduces air leakage while adding to the insulating value.
The "leakiness" of the home was assessed measuring its "air changes per hour." That represents the number of times the total volume of air inside the home escapes in a one hour period, with windows and doors closed, when the home is pressurized with a fan. To meet the Net Zero program requirements the number of air changes must be less than 1.5 per hour. MacKenzie's home tested at 0.6 air changes per hour.
Once the envelope is designed to minimize the heating and cooling needs, efficient mechanical systems are chosen that minimize energy use. A heat recovery ventilation (HRV) system was used to bring fresh air comes into the home, and send stale air out, while ensuring that heat is exchanged in the process – to reduce energy waste.
Solar energy is used to pre-heat water before it goes into the hot water tank, and a drain-heat recovery process transfers warmth from used grey water to preheat the incoming cold water. An air-to-water heat pump adds any additional heat required to ensure that the domestic hot water is always at the right temperature. The same air-to-water heat pump also heats or cools water for the in-floor radiant heating system – heating in the winter and cooling in the summer.
And, lastly, to meet the net zero goal, MacKenzie installed photovoltaic panels on the roof that can generate nearly 11 kilowatts of electricity.
Using modelling to solve the puzzle
MacKenzie explained that any house can be constructed to be net zero if "you throw buckets of money at it".
"But that's not the point," he added.
Rather, builders can work with their energy advisors and designers to identify the most cost effective solutions that will meet the needs of their clients.
Figuring out what combination of construction elements come together to produce a building that can generate as much energy as it uses is simpler than you might think. Computer programs allow for architects, designers, and builders to virtually test their plans in models.
"You can play with different options at the modelling stage," he said. "That's how you find systems that will work without breaking the bank."
With the Buchkowsky home, MacKenzie ran 13 rounds of modelling, each time changing wall configurations and insulation, until he got the combination of components that helped him achieve the net zero requirements.
The Saanich home was the first to be labelled as a Net Zero Home, a program from the Canadian Home Builders Association (CHBA).
For nearly ten years, Falcon Heights has been part of the Built Green program. "We've been consciously working on improving envelope and air quality," he said. "We try and improve the performance of each house we build."
While constructing a home that is energy efficient sounds good on paper, he explained, "comfort trumps everything". It so happens that a well-built, energy-efficient home is also more comfortable and enjoyable.
Especially with a view like that.