Thermal walls, or Trombe walls, are the single most flexible passive solar option: they work in any climate and on any home, providing extra heat throughout the night after gathering heat during the day.

Although thermal Trombe walls work well in all climates and for almost any home, you need to choose the correct design for your particular needs. This choice depends on your local climate. Here are some essential guidelines:

In an ideal passive solar world, homes would be built as a long string of single rooms, so that every room would be heated by the sun and there would be no need to transport warmth from warmer to cooler rooms. In practical terms, long houses are rarely appropriate: traffic flow inside such buildings is often difficult and housing lots in towns and cities tend to be square or rectangular, rather than extended oblongs.

Physics is the science that defines how the physical world is structured and how each part of it interacts with all the others. Unfortunately, it's an incredibly complicated science because of this. The world is a very complex machine, after all!

As far as solar designers are concerned, there are some very basic laws of physics that must be understood. If you are a newbie in the solar energy field, here's a brief primer for you.