April 01, 2009

The energy efficient ‘envelope home’ is back!

Posted to Julie Sarton

Back in the 1980’s energy efficient homes seemed like the wave of the future. Once high fuel costs and interest rates dropped back to normal, however, they seemed to have become almost obsolete. In the last ten years of more prosperous times, I probably couldn’t have told you what my monthly heat bills were. How times change! Faced not only with a brutal economy today, but also with a growing moral obligation to conserve our energy resources, energy efficient homes are back in style and demand.

One alternative to a solar home with large, expensive roof panels is the thermal envelope home. Although it was a popular design theory in the late 1970’s, few envelope homes were actually built at that time. The construction principle is one of a house-within-a-house. The north and south walls are double, with a continuous air space of 6-12 inches going through these walls, the roof, and the floor. In many of these the south-facing airspace was actually a sun-catching space, such as a glassed-in solarium. During the day the sun heats the air in the south sun space, which then circulates in a convective loop around the home releasing the heat. Although this design is more expensive to build, these costs are recouped over time due to the low energy needs.

I recently listed an envelope home in Williams Bay, Wisconsin. With square footage of around 2350, the monthly heat bills averaged only $70 last year. Since the residents liked to keep the temperature over 70 and did not turn it down at night, this figure could have been a lot lower. Solar energy is not only a renewable source, but it’s a path to clean energy and may once again play an important role in home design. Get out the sun tan lotion!

Posted By: Julie Sarton

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