Charles McLaren
Re: Yukon to exempt log homes from energy efficiency rules, Jan. 16
The Yukon government has taken a reasonable stand, and level of exemptions, for log building construction in the territory. People should be able to build whatever they want for their personal use, providing it is safe. If a person chooses to waste energy, that’s their call.
Have no doubt that log buildings are energy hogs. Those who claim that solid log, stack wall, rammed earth and similar constructions are energy-conserving in our climate are all drinking the same Kool Aid.
As background, in addition to having designed all manner of construction types as an architect, including log houses, my first degree is in physics. Physics includes thermodynamics, which is defined as the study of heat, its behaviour, transfer, and conversion to other forms of energy. While esoteric physics is in a state of flux, the basics, like heat transfer or gravity, are well defined and understood on the level we experience them.
Dave Loeks’s comment that “there are other energy, physical characteristics going on, that aren’t really well understood, that boost the energy performance in a way that isn’t captured by focussing on R-values” is wishful thinking. I wish unicorns would come over the rainbow and put a pot of gold on my doorstep, but that will happen about the same time a log home has low heat loss.
Contrary to Loeks’s assertion that the building code is “designed around… fiberglass or foam insulation,” it’s based on reducing the passage of heat from inside to outside, to save energy and money, and preserve the environment. An R-value is a measure of resistance to heat loss.
While log builders and their kin will make extravagant claims for energy savings, what they never offer is instrumented testing to back it up. Other groups, such as the National Research Council of Canada, the U.S. Department of Energy and the University of Alaska (Fairbanks) have all tested log walls and they’re not stupid people. Nor are they making money from selling log homes.
The International Log Builders’ Association (ILBA), surely a group that has an interest in selling log homes, agrees with that research. Try reading their Log Building News No. 38, August 2002.
What are the facts? In the North, a log has an insulation rating of R1 per inch. An 8-inch log equates to about a 2- or 3-inch fiberglass-filled wall. This doesn’t include loss from leakage as the logs shrink, wasting more heat to the outside.
What about those other mystical characteristics? That’s thermal mass, and it’s not free. A dense log wall can act as a heat bank, absorbing and storing heat, to release it later. That’s why people get the impression that a “log house holds the heat” - it will cool down slowly. It also heats up slowly, as you replenish the “heat bank.” Just like your bank account, you have to put heat in, to get it out later. All the while, the log house is continually passing a lot more heat to the exterior than a frame house, requiring greater energy input.
How much is thermal mass worth? The ILBA paper notes that in a climate with about 6,600 heating degree days, such as Whitehorse, it might add eight per cent, bringing the R value to R8.5 for an 8” wall.
The cost of heating and maintaining a building over its lifespan far outweighs the initial costs, so the claim that “the environmental footprint of solid wood is a fraction of any other building technology going” sounds good, but is dubious.
This is a subject I broach delicately with design clients. I’m with the client who said, “I know they waste energy, but I really like them.” That, I can get behind.
For those who insist that a log home is an energy saviour, I have a slightly used unicorn to sell you.
Charles McLaren is an
architect in Whitehorse.