• to the sun, darker colors in the shadier areas to capture reflected energy.
• Avoid covering thermal mass. Carpets effectively make floor mass useless.
• Plaster and stucco do not significantly reduce solar gain, but drywall does unless very tightly fixed to the surface.
• Use the solar glazing percentages above to work out how much mass you need.

In retrofits, you may have to estimate or guess how much mass you have as furniture, planters and other incidentals. Try to be as accurate as possible.

Overhangs

An overhang determines when your solar heating season starts and ends. They should always be a little higher than the top of the window so that the low winter sun can get underneath and hit the whole window.

The calculation for the size of an overhang is fairly simple, but relies on your latitude to determine an "F-factor" range (see table). This range covers less sunlight at the low end and more at the high end, allowing for some design flexibility. The overhang size is calculated as follows:

Overhang projection = Height of window ÷ F-factor

This is a basic design, of course: the distance of the overhang above the window and the actual local conditions can make a significant difference, especially when tied in to your particular design and solar gain requirements.