DESIGN:

Exterior treatment:   You have sited the proposed building with one long side facing south, or nearly south, and the peak of the roof running East/West. Also, you have limited the trees on the south side, as suggested in the Setting chapter.  Now, out of the hundred and one design decisions that you will have to make, there are a few that are important to your future energy costs, and to keeping temperatures comfortable.

For example, placing windows and glass doors:  On the South side, install lots of windows and glass doors, as many as you wish. The solar heat that they will gain when the sun is shining is greater than the heat that they will lose when the sun is not shining: Provided that all of the units have double-glazing or triple-glazing of good quality, and are well-sealed in their frames.  (Go to Insulation for window details.) And, provided that there is a roof extension over the south wall, reaching far enough out to prevent any direct sunlight from entering the windows and glass doors in the summer.  Without this important feature, the discomfort and/or expense of summer cooling will cancel out the heat savings that the sun provided during the winter.

Go to Solar Angles for a table showing sun angles throughout the year in the Temperate zone. There you will see that the sun is at so high an angle in summer that it takes very little to keep it out of the south-facing windows.   In the winter, on the other hand, the sun is only 25-30 degrees above the horizon, and it will come in under a 30-inch overhang.

Here is a practical application of the roof overhang:  We recently had a cape house built for us at latitude 42ºN, just south of Boston, Mass. We designed it with a lot of glass on the south wall, and had the builder site the building so that wall faced almost directly south.  At our request, the builder extended the south roof of our ranch from the usual 8 or 9 inches to 24 inches of overhang, including the gutter.

Now, from June through mid-September, the sun does not shine in through any of the south-facing windows.   As for the glass slider, during that period, the sun comes in only through the bottom 12-14 inches.  From November through April, the sun pours in through every one of the south-facing windows.

The little shovel is a 25” fireplace tool.

For windows that do not face south, each square foot of glass, even double-glazed, loses about five times as much heat per square foot as a well-insulated wall. Further, in the heating season, there is very little compensating solar gain through windows that do not face south.

So, other things being equal, try to limit the glass on North, East, and West walls. 

For the five or six warm months, the West end of the house will experience an extraordinary input of solar heat toward the end of the day.   It can make decks and sitting rooms very uncomfortable, unless extra measures are adopted to keep out the sun. The western sun is so low after about four o'clock that completely opaque white window shades pulled down to the sill are necessary, in order to minimize solar input at the west end of the building.  Without those shades, the west rooms will get much too hot, or an extra ton of AC will be required, or both!

The basement is a special case. Concrete is not a very good insulator.  Insofar as practical, backfill the earth as high as possible around the outside, perhaps six inches below the wall siding.  (Less than six inches of exposed concrete is an invitation to termites).

There is extended discussion of foundation insulation under Shell. To summarize, if your space- and water-heaters are in the basement, and/or if you plan to have a laundry and tool shop there, it is better to insulate the basement wall than the ceiling of the basement.   Incidentally, many building codes specify ceiling insulation, but allow wall insulation instead, provided that the total of the R-values is 15.

Another design feature deserves mention, and that is skylights.  Aesthetically, they can light areas that might otherwise be uncomfortably dark, although that applies only during daylight.   However, from an energy standpoint, they are not good.  In the warmer months, when the sun is high, solar heat pours in through that southerly window in the roof.  The light is nice, but the added heat is not nice.   It can be uncomfortably hot, and one skylight can add one ton to the air-conditioning load. 

In winter, on the other hand, the sun is fairly low in the sky. Very little direct sunlight will enter the slanted skylight, and no heat will be added to the space.  In fact, the heat loss through the glass is many times the loss through an equal area of insulated wall or ceiling.  Add to this the fact that temperatures at the top level of a room are apt to be well above the 70-degreeF norm, and the heat loss is even more pronounced.

In summary, a ceiling light with high efficiency bulbs will cost a lot less over the years than a skylight, and it will be a lot more useful at night.