Sunday, December 7, 2008


For those who want a change from the usual hot and humid months in central Texas we are finally getting some cool weather. Instead of sweating profusely when going on a walk or run, now the cool dry air keeps us comfortable. Unfortunately at night though, the temperature drops and the heating bill can creep up while indoor comfort can deteriorate too.

Much of the focus on home energy efficiency in our area is on keeping houses as cool as possible in the summer months. Some of the strategies for this like adding insulation also tend to help keep homes warmer in the winter. Others like shading windows with solar screens which help in the summer act as a detriment in the winter. In my house for instance, before I had an aluminum coated metal roof installed my house would heat like a furnace in the summer due to the radiant heat of the sun super heating my attic through the roof. Now that the metal roof is on, much of the sun's radiant heat doesn't make it to the roof decking. The summer heating problem is gone and even without the a/c on the house stays cooler inside than the high temperatures of the summer days outside. But, now I've lost the effects of what was in effect a big solar heater in the winter too. More attic insulation was needed to compensate.

This emphasizes the importance of understanding a house as a system that has to interact with a variety of conditions outside. Any changes made to make a house more efficient need to be understood in the full context of other parts of the house and with all seasons and weather conditions in mind. Questions need to be asked such as whether solar screens are necessary if the overhangs of a home are sufficient to block direct sunlight from hitting a window in the warm weather months. Shading windows in the summer if they get direct sunlight is very important but allowing sunlight in to naturally heat the home in the winter is also important. Usually passively heated homes will have minimal windows on the north, east and west sides of the home but a plethora of them on the south and southwesterly facing sides of the home. This is due to the arc that the sun appears to travel over the home at different times of the year. In central Texas the sun has a higher and more northerly arc in the summer and a low and southerly arc in the summer. Having south facing windows with properly designed overhangs allows little sunlight in the summer but plenty in the winter.

All this being said there are several home improvements that can be made to a home that will help keep it warm in the winter and cool in the summer such as:

1) adding attic insulation
2) sealing ducts to the mechanical system if one is installed
3) sealing passageways that outside air can easily travel into the home
4) eliminating "thermal bridges"

There are numerous ways for addressing all of these situations. Again this emphasizes the importance of looking at the whole house as a system and addressing the specifics of each house with a comprehensive plan.

Feel free to call us at 512-467-0005 or email at if you would like to discuss this more.

Curt Van Riper

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