The renovation that’s going on at Terrell Wong’s Rosedale heritage home isn’t the kind you usually see in Toronto: the square footage hasn’t been doubled, there’s no added stucco involved, and many of the original fixtures and cabinetry are being reused. But then, Terrell isn’t your normal homeowner — as an architect, her firm, Stone’s Throw Design Inc., designs “green” homes and along with Ann Stevens and Clelia Lori won the design competition for the Archtype House now fully built and operating at The Kortright Centre. So Terrell knows a thing or two about building energy efficient homes.
When the opportunity arose to renovate her in-laws’ home, Terrell set her goal at insulating her house to as close to Passive House standard as she could get. The goal of passive house design is to construct a building envelope that’s so tight a homeowner only needs 15/kwh/m2 of energy to heat the home. To put that number in perspective, right now Ontario building code minimum standard is 150 kwh/m2 (yes, that’s 10 times passive house standard). The Rosedale House won’t achieve such a low energy use, but it will achieve a 50/kwh/m2 energy use. FYI: passive house standard is difficult to achieve in our climate. It was developed 20 years ago in Germany which has a moderate climate than ours. For more information on Passive House see: http://www.passivehouse.us/passiveHouse/PHIUSHome.html
So, how is Terrell going to achieve this low energy use goal?
Building Envelope: The interior walls of the house were completely torn back to the brick. The walls are being insulated with 5.5 inches of Heatlok Soya insulation (R6 per inch) for an R value of 33. The attic will have 2 inches of the spray foam in addition to cellulose insulation for a projected R60. In the basement they dug down three feet to add some living space without going out back, and placed 4″ R10 rigid board insulation in the floor, then covering it with radiant infloor heating tubes and a final layer of concrete (which will also act as the final floor finish.
Terrell’s blog is a goldmine of green building information. She’s described the reasons behind why she decided to do certain things and who she used to do it. Getting the right trades involved in a project like this is essential to its success. Terrell talks about why she needed to use spray foam insulation versus batt insulation such as Ultratouch or mineral wool, which would have been a lot cheaper, but also you’d lose a lot of space. It all comes down to air leaks and let’s face it, old homes are full of them. Like many old Toronto homes there was minimal insulation in the attic, no insulation in the brick walls and none in the basement. In fact heating used to cost $7000 per year, using two big oil tanks which were filled 4 times per year. Using a minimum of 5.5 inches of spray foam achieves several goals:
- It can get into cracks and crevasses that batts can’t and really seal them up.
- It can be used as a vapour and air barrier at two inches or more thick.
- You do not need to rely on the coordination of many different trades to identify and seal leaks. The foam accomplishes it all in one go. This is particularly important in the renovation of an older home.
Thermal bridging: thermal bridging refers to the areas where heat can travel and escape from enclosed spaces to the exterior. In most older homes thermal bridging occurs where internal wooden beams touch the outside masonry. This is particularly true for floor joists. The Rosedale House’s new construction has the internal 2x4s spaced 2 inches away from the external wall so that 2 inches of insulation can go between the studs and the wall, thereby minimizing heat escape.
Energy Recovery Ventilator (ERV). When an energy audit was performed before the house was gutted, thanks to the absence of insulation, 8 air changes per hour were measured — that’s a really leaky house. When the renovation is completed, air changes per hour will be reduced to 0.6. When you have a building envelope that’s that tight, you need to make sure you have fresh air coming into the home at all times. But in the winter, opening windows defeats all the hard work that’s gone into insulating the home, so a practical device is an Energy or Heat Recovery Ventilator (HRV/ERV). Fresh air from outside is pulled into the ERV and warmed by outgoing old stale room temperature air. The model of ERV that Terrell chose is by Ulimate Air, the RecouperAerator 200DX which is 96% efficient at heat exchange from air and moisture.
A tighter envelope means that a smaller system is needed. A new 12 kw electric Allied boiler Ministar will provide all the heat for the house, and a two tank hot water system that was imported from Germany will provide hot water. The two tank system provides one tank with “preheated” water from future solar hotwater heater on the roof, and a tank for conventional water heating.
As with the whole process of renovating this house, Terrell has reused as much as possible. The kitchen cabinets are going back in (although with a fresh coat of stain!), and all the radiators are being reused. Further, the small rebuilt addition at the back of the house will be sided with the tongue and groove wood that’s on the ceiling of the covered porch that needs to come down. But the huge, west-facing window will be imported from Germany, made to passive house standards. (Manufacturer: Internorm Varion windows http://www.greenbuilding-windows.com/products/greenbuilding-windows.html)
It will be fantastic to watch the progress of this house. Terrell’s blog gives an excellent explanation of why she’s chosen particular materials and mechanisms, as well as (and most importantly) what trades she’s worked with to achieve her energy efficient dream house.
I will be following her progress as she goes. Thanks for sharing Terrell!
You can reach Terrell at: Stone’s Throw Design Inc: 416-463-9735
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