A South-Facing Building Lot -Resources (Education)- E

Solar Home Chronicles 3

Tuesday, 25 September 2007

The passive solar home must be oriented on its lot so that most of its windows face south. This means that the ideal lot will have a vista or space on the south side of the building, so that the sun can shine on the south wall, unimpeded, through the fall, winter and spring. We had this in mind when we began to look for a suitable building lot for our solar home.

But, when you think about it, every lot has a south side. So wouldn’t every lot have potential for a solar home? The answer is yes, if you are comfortable having a house that does not necessarily sit squarely on its lot. We imagined that, here in Sackville, if we decided to build a house that sat on an angle from a crowded residential street front, to take advantage of a south exposure, we might get some negative responses! So we looked for a lot where we could build our house somewhat square to the road.

Outside of Halifax, there is a “solar subdivision”. One of its covenants is that you cannot have your house sitting squarely on its lot. Every house has a skewed orientation, and when you look down the street, you don’t see flat fronts of houses – you see them sitting every which way. This makes it easy to design for the sun on virtually every lot in the subdivision.

There is a good reason why we want a full south exposure. When the sun hits the glass of a window, some of the energy (heat) goes through the glass and some of it is bounced back away from the glass. The amount that is allowed through the glass is at its maximum when it hits the glass squarely. So a south-facing window will allow in its maximum solar gain at mid-day, and less so as the sun is angled away before and after noon. Double- and triple-glazed windows, because of their layers, actually let in less energy than single-pane windows, but their additional insulation (not letting heat back out once it is in the house) more than makes up for this lessened gain.
Actually, Solar Nova Scotia experience shows that with the new double- and triple-paned windows, with argon or krypton gas in between the panes of glass, you can deviate from absolute south by as much as 15 degrees, and still get significant gain from winter sunshine. So we will have some leeway on our lot, as we plan for where our house should be situated.

When we went lot-hunting last spring, we had only a few choices in town. We were lucky to find a lot near the golf course, that is a big field with a woodlot at the back. This means that there is ample space for a house, we won’t have to cut down any trees, and we can utilize the town water and sewer systems.

One drawback with this lot, though, is its lack of shelter from the cold north wind. The ideal lot is protected on the north side, so you will often see solar homes that are actually backed into a northern hill as protection and insulation. And the roof will be sloped, so that cold north winds whoosh up and over the roof, instead of pooling against the walls.

We will have to push soil partway up the northern wall of our house (in a berm), to give it some added insulation. And, from the road, a long, sloped roof may end up being the most dominant feature of our home. At the very least, we will have to plant some trees on the north side, for protection from winter weather.

… more about how to take advantage of the micro-environment of your lot in my next instalment…