There have been a few questions about heating systems and heat distribution recently. I asked Canada’s green building grandfather if I could publish a paper that he wrote about how heat gets distributed in an advanced home. For your reading pleasure, written by Rob Dumont of Saskatchewan Conservation House fame:
The temptation has always been there for eco-house builders. It’s those damn windows; they are just so useless once the sun goes down. There must be some way to insulate them once they no longer need to be seen through, right?
The answer is yes, but not cheaply. The biggest problem is moisture. If you insulate a window from the inside without a perfect air seal between the heated space and the cavity between the window covering and the window, moisture-laden air will flow into said cavity. When that happens, the moisture will condense on the window. Take it from green building pioneer Rob Dumont:
Back in the 70s I had a small house with lots of south windows. I experimented with interior rigid insulation on the windows. Some observations:
You need a very tight air and vapour barrier on the warm side of the insulation. I did not have either, and condensation would readily form on the window. I used a 2 inch thick piece of beadboard as the insulation. The windows were double glazed sealed units with an R value of about R2. Even more condensation would form on the window when the insulation was removed, as the warm, moist air could then, unimpeded, hit the window. The condensation would run onto the sill. I actually got quite sick from the mould that grew on the lower corners of the windows. Never again.
We felt compelled to buy window coverings as soon as we moved into the Mill Creek NetZero Home read more... »
Editor’s Note: I’ve written about Rob Dumont in the past. He is one of the fathers of the green building movement, and I’m very pleased to have permission to reprint one of his columns here.
By Rob Dumont
Have there been any recent advances in the area of passive solar heating for residences?
Passive solar heating has been known since the time of Socrates. However, it is only slowly catching on in Canada. Improved windows have made the recent advances possible.
In the 1970s there developed two schools of thought regarding how best to reduce space heating bills in residences using passive means. One school was called the “mass and glass” school. With this approach, large south facing windows would be used along with concrete slabs and heavy construction such as adobe. This school had a lot of proponents coming out of the south-western United States. New Mexico was a hotbed. New Mexico has an especially favourable solar energy climate and relatively mild outdoor temperatures compared with most of Canada. A photo of the David Wright Home in Santa Fe, New Mexico, is shown in Figure 1. In Figure 2 a cross section of the house is shown.
Figure 1. South exposure of the David Wright House in Santa Fe, New Mexico
(Photo Credit: Design for a Limited Planet, Skurka and Naar, 1976)
Figure 2. Cross Section of the David Wright Mass and Glass House
( Credit: Design for a Limited Planet, Skurka and Naar, 1976) read more... »