Houses without Furnaces

So far we’ve been quite lucky –  the fall has been mild, and it hasn’t been until the last few days that winter has really struck. However, with all the white stuff on the ground, temperatures are only going to fall, and our heating bills are only going to rise.

In the last article, we learned how the city of Munich has taken a lead in becoming energy self-sufficient. There are two key concepts involved: generating as much power as possible from renewable resources (wind, hydro, solar and geothermal), and reduction in the demand for electricity through the construction of “Passive Houses”.

The concept of a Passive House comes from Germany, where the climate is quite similar to our own, here in southern Ontario.

Simply put, the Passive House (das Passivhaus) is one that needs no furnace or other heating equipment to maintain a comfortable indoor temperature.

The closest equivalent in Canada is the R-2000 house; however, the R-2000 standard still falls far short of what is being achieved in northern Europe.

A properly designed and constructed Passive House should need no more that 15kWh/m²/year (15 kilowatt hours per square metre per year). A fifteen hundred square foot home built to Passive House standards in Cornwall would cost about $220 per year to heat (less than $20 per month) at current rates. Compare that to your current Cornwall Electric or Union Gas bill. Remember too that energy prices are only going to increase, so the time will come when you can sit comfortably warm in your Passive House when the rest of the population is either freezing in the dark or going bankrupt.

There are three keys to the Passive House: superinsulation, passive heating, and active ventilation.

Insulation, by definition, slows down heat flow from a warm area to a cool area. No insulation is perfect,however, the more you have, the easier it is to stay warm in winter, or cool in summer. Ontario is the only province to specify minimum insulation levels for houses. Under the current building code, roofs need a minimum RSI of 7 if conventional heating is used (typically gas or oil), and an RSI of 8.8 if the house is heated electrically. After January 1, 2012, these figures will rise to RSI 7.24 and RSI 9, respectively. Most Passive houses have roof insulation of around RSI 9, so the province is making some headway in this regard.

The province is behind with wall insulation. Currently walls need only RSI 3.34 or RSI 4.22 for houses with conventional heating, depending on whether it’s in southern or northern Ontario. For electrically heated houses anywhere in the province, this jumps to RSI 5.10. By contrast, true passive houses boast wall insulation values of around RSI 7 (R40).

Window insulation is far behind the best European Standards. Passive house windows boast an R-value of around 7.5 (RSI ~ 1.3), whereas the best on the Farley Windows website is only R3.85 (RSI ~ 0.68). The European house windows will allow more heat into the house during a winter’s day than they lose at night, and of course during the summer, they are shaded to prevent the house from turning into an oven. It is this passive heating, along with the heat produced as waste by lighting, appliances, and even people, which allow these houses to be comfortable in winter without a furnace.

The biggest problem with a properly insulated house is air exchange. If the air within the house is not ventilated properly, and replaced by fresh outside air, the atmosphere within quickly becomes unacceptable and unhealthy. Both Passive Houses and R-2000 houses have an active heat/air exchanger. This is a small unit which pumps air out of the house, but captures the heat in this air and uses it to warm up the outside air coming in.

Next column, we’ll talk a little more about Passive Houses, and what you can do to help your current house approach these standards

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