A trombe wall is a simple concept and one that I have personally experimented with; it is also a project that can have a very quick payback, a rare thing with alternative-energy investments. A quick search on Google Images will reveal that there are numerous and diverse designs approaches for trombe walls. Ideally, the glass should be on a South-facing wall and in front of a masonry surface; the idea is that the masonry surface will absorb excess heat during the day and then radiate that stored heat into the home during the evening hours. My situation was not ideal. And that brings me to my main tip.

My advice for retrofitting this project to an existing home is you can't go wrong if you cover a large enough area for minimum cost. So that raises the question, where can you buy cheap windows? A great thing about the window replacement business is they keep salvage supply stores filled with an endless supply of windows; and because they get so many they almost have to give them away. I have been visiting a salvage supply store in my town for several years and the supply never ends; they have to clear them out every couple months but you can always make a deal. Some of these windows are newer, double paned, and of good quality.

Now that a potential source for cheap windows is identified, let me explain why I believe you can't go wrong with this project if you have some carpentry skills. Again, my situation was not ideal, I have an older wood-frame house (no masonry walls), and the only wall that sort of faces south is partly shaded at times of the day. However, I was curious and wanted to see for myself if this really works. My first mock up was an extremely basic experiment; a 20' x 10' clear plastic tarp was attached to the soffit and allowed to hang down from the soffit to the ground; some jerry rigging ensued to seal the sides and bottom of the tarp from drafts. Simple as it was, the effect was immediately apparent. I still think about this when I hear about people on fixed incomes struggling to heat their homes! Although quite humble looking, it was in my back yard and I could have left it there for the season and benefited from dramatically reduced heating bills. But I was convinced; I immediately began thinking about design options.

My design philosophy was simple, maximum square-foot coverage for minimal cost; I was able to cover an 8' x 16' wall (128 sq. ft.!) for about $150 in glass and another $100 in misc. materials from Lowes. The heat gained from this project was immediately apparent and dramatic. I did not cut holes in my wall as this was dismantled at the end of the season; instead I simply opened a window to let the heat in; sometimes a fan was placed in the window as well.

With most alternative-energy investments requiring several years of energy savings to pay off, this is one project that can break even in one winter season. It's also great to feel a very warm wall heated with the sun, a clean, renewable resource.