The attic of your house has probably got ventilation in the form of a louver or two – in fact, Building Codes just about everywhere require it. You may even have seen those spinning ventilators, which are very common in the hot climates, such as that of Arizona. The idea is good, but have you ever considered how effective these passive devices are in doing their job?

The concept is simple. In the summer, the sun beating down on the roof ensures that it is much hotter in the attic than it is outside, and this heat goes through the ceiling into the rooms below, adding to the air conditioning load. By providing several openings into the roof, you allow airflow through it, with the idea of reducing the temperature. The trouble is that you are also relying on some sort of air movement to make the hot air move out of the attic. Sometimes the roof ridge itself has openings, with the thought that the hot air rises, so air will flow out of the ridge and replacement air will come into louvers positioned lower. Great idea to help with the air movement, but you have to have an already hot attic for it to work, and there’s not a lot of height in many roof spaces to create that natural current. So you’re back to waiting for the wind.

keep cool with a fan in the attic

Photo: by graur razvan ionut

It is obvious that an answer to the problem of moving the hot air out of the attic is to install a fan on the roof or on the gable end. Properly positioned, and with your louvers on the side opposite, to make sure that all the attic space gets ventilated, this would pull the temperature down towards the outside air temperature. The trouble with this is you need to provide electricity to run the fan.

As you may have guessed from the title, we have found an answer to this problem. Why not just install a solar attic fan? These neat devices are solar powered, with a fan mounted on the roof, and a solar panel for power mounted on the fan, the whole provided as an integrated unit. You need to put the fan on the South side of the roof for best exposure of the photovoltaic panel to the sun, or you can also get a solar attic fan with a mounting bracket for the panel, which allows you to point the panel towards the sun. This is true fit-and-forget, all you need do is to enjoy better comfort and lower cooling bills in summer.

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