I mentioned in an earlier post that Terrell Wong was retrofitting her husband’s family home to have a building envelope that’s almost as tight as a Passive House’s home. While I was visiting the Rosedale House, I became intrigued by the whole idea of Passive House design and its possibilities in a Canadian climate. Terrell took time out of her (extremely) busy schedule to talk to me about Passive House design and its relevance in our Canadian climate.
Passive House designation was developed in Germany twenty years ago. While it is just gaining attention here in North America, it has been the standard of choice in Germany since its inception. There are a few reasons for this: one is that electricity, and energy in general, is far more expensive in Europe than it is here so it’s in the homeowner’s best interest to build the tightest building envelope technology can offer. Another reason is that in Germany’s milder climate, it is more technically feasible to build a house that uses only 15 kwh/m2 of energy for heating and cooling. Thirdly, and perhaps most importantly, building codes are much tougher in Germany and require higher levels of insulation and energy conservation than we have here in Canada (hint, hint Canadian building code writers).
The reason that 15 kwh/m2 per year was chosen as the passive house standard is that a boiler or furnace is no longer required to heat a home at that level. In fact, home orientation with south-facing windows, an energy recovery ventilator and occupant body heat can be enough to keep a home warm except for on the coldest of days.
Building orientation and heating requirements: Here in Canada, particularly in an urban setting where property choice and development is restricted, building a passively heated home is a challenge. As a contractor I know says “Anything’s possible, it’s just a matter of how much money you’re willing to spend.” In Terrell’s case, she was restricted by the fact that her home is east facing, something that was completely out of her control. Passive homes are designed, when possible, to take advantage of the sun’s rays in the winter with south-facing windows that allow for heat absorption during the day. In the summer, the planting of deciduous trees and awnings can help block the sun.
Insulation requirements: Sometimes getting the insulation levels to where they need to be for passive heating doesn’t make financial or spatial sense. Naturally, colder requirements require much more insulation and sometimes, giving up the space due to thicker walls can be an issue. For example, depending on the climate in which you live, if your home requires R60 in the walls to meet the standard, your wall may need 10 inches of R6 insulation which can take up to 2 feet of space away from your living area by the time you’ve added exterior and interior walls (not to mention the cost!).
But working towards building a tighter, well-insulated envelope has the advantages of providing significantly lower heating bills. As energy prices rise, a well-insulated home can also insulate the homeowner from sky-rocketing energy prices.
Thermal Bridging: In addition to building orientation (to take full advantage of the sun), building envelope tightness and insulation, passive house design also addresses thermal bridging. Thermal bridging occurs when heat finds a path to escape out of its enclosure. Thermal bridging occurs around and through windows and doors, as well as floor and wall studs which are attached to the outside part of the building envelope. Eliminating these thermal bridges is a key element in passive home design. Homes are designed with as few if any electrical wiring running up the outside walls.
Windows: In Germany there are Passive House certified windows. Because Passive House design has existed in Germany for so long, the window manufacturers’ technology has evolved to match the requirements. While there are distributors of these windows in Canada, getting a contractor who understands how to properly install them is essential for a sealed fit.
I came across an article on windows for passive house design by Martin Holladay, from Green Building Advisor. There are five Canadian companies that manufacture high quality thermal windows that, while not Passive House certified, offer superior insulation properties as well as fiberglass frames. Fiberglass is considered to be one of the best materials for window frames as it expands and contracts at the same rate as glass helping to reduce thermal bridging. For an excellent explanation on windows for Passive House design, see Martin Holladay’s blog post in Green Building Advisor: Passivehaus Windows: Cold Climate Builders Look for the Best Available Windows.
Modeling: If you’re at all interested in pursuing Passive House design, the first thing you need to do is input your home’s design (including orientation) through the Passive House Planning Package. This is an energy-simulated model run in Excel that will provide you with your heating load/m2 based on the figures you input. It will also calculate your overall costs assuming you know your costs/m2, so you can make informed decisions about whether it’s more economical to increase your insulation or invest in better windows. Note: this is NOT a do-it-yourself kit. It takes considerable specialized training and engineering knowledge to use this software properly and understand the results. It’s best to work with a certified Passive House designer, consultant or architect or engineer who is familiar with passive house design and modeling if you’re interested in building a passive house.
Building, or even retrofitting a home to passive house standards may not be realistic for most of us, but if we can strive to increase the insulation in our homes, recognize and avoid thermal bridging and invest in the highest quality windows our budget can afford, the upfront costs might be higher but the pay-off will continue for years to come.
For more information on Passive House design see:
Thanks again Terrell for your time and expert knowledge!
Feature photo courtesy of ssirrpassivehouse.blogspot.com/