Shadows and Planning a Passive Solar House



Before we get into shadows, it is probably important to define passive solar. When most people think of solar power for homes, they think of panel systems on roofs or in the yard. This mental image has nothing to do with passive solar. Passive solar refers to a home or structure that is configured and designed to naturally harness the power of the sun in the form of heat. Technically, there should be no panels, but some will use them as an add-on.

When planning a passive solar structure, one of the most important things to consider is shadows. This is a simple way of referring to how the home will sit on the land I assume you have already purchased. The configuration of the structure to the property should be such that the longest side of the home with the most windows receives the most sun. This maximizes solar radiation penetration into the home, to wit, maximizes the amount of heat that can be captured. There is a simple test to determine this.

To develop a guestimate of how the home should sit on the property, go out and stand on it in the middle of the day. What direction does your shadow extend in? The opposite direction represents a general guide to the direction of the sun. The longest wall on your structure should run perpendicular to this direction.

Importantly, this is only a guideline to configuring your property on the lot. Do not rush off and get architectural plans done based on this guestimate. The angle of the sun to your property will change during the year as the Earth tilts in different directions. While you now know the general layout you should use for the property, make sure to follow it up with a professional analysis of the position of the sun throughout the year.

When it comes to harnessing the inherent power of the sun, much of the discussion focuses on angles. Maximizing sun penetration into your home is the particular key when it comes to passive heating through solar.