Attic vents come in a wide variety of styles to accommodate the ventilation and aesthetic requirements of the wide range of roof designs and configurations. A curious person may ask why we ventilate our roofs, or more accurately why we ventilate our attics. Generally, the simple answer is that the cooler the attic is, the less temperature differential there is between the attic and the living space in our home, and our air conditioning system operates more efficiently and economically. So then, the next question is how to best ventilate the attic? No simple answer here – it really depends on the roof configuration. So, let us look at the basic types of attic vents and how each works:
Turbine vents – otherwise known as whirlybirds, they resemble metal mushrooms on the roof up near the peak, that spin around (and sometimes rattle and squeal). They have been used for years and work on the principle that hot air rises and gets released through the turbines. They work even better when there is a bit of wind to help spin them and vacuum the hot air out. Very dependable and cost nothing to operate.
Ridge vents – these are long slits cut in the roof along the top ridge, which are covered and protected to keep rain and critters out. They are usually covered with materials like the roof covering, to blend in with the roof. They work on the same rising hot air principle of the turbine vents and can remove large volumes of hot air from the attic, if you have enough length of ridge on your roof.
Power vents – these vents come in various sizes and shapes but are basically vents with an electric motor to turn them and exhaust air from the attic. They are usually controlled by a temperature sensor that turns them on or off, depending on the attic temperature. They do of course cost something to operate, as the motor runs on electricity.
Gable vents – these are vents installed in the flat wall surface of a gable wall and release hot air much the same way as the turbine or ridge vents. They are available in different shapes and can be quite decorative. They often serve more of an aesthetic purpose, being located lower down the wall and therefore may not be as effective at getting the hot air out of the extreme highest region of the attic.
Soffit vents – these vents are located low on the roof, down around the perimeter of the house. Where all the above-described vents are exhaust vent that let the hot air out, soffit vents are intake or supply vents that let in cooler air to replace the air leaving the attic. They are critical, as the attic cannot properly ventilate without enough supply air. Without sufficient replacement air coming in through soffit vents the attic air will stagnate, retain higher levels of vapor pressure (humidity) and possibly create a multitude of other problems throughout the house. In extreme cases, some attics ventilated with power vents have been known to pull air from the conditioned regions of the house if enough supply air is not provided. Generally, you need a good 50/50 balance between the soffit vents and the exhaust vents. Cooler air comes in through the low soffit vents and the hot air goes out through the higher vents, just like a chimney.
Attic ventilation can be critical in the overall efficiency and function of your house environment. Building geometry, second floor conditioned spaces and placement of mechanical equipment, if installed in the attic, all contribute to the function of your attic ventilation. Qualified professionals should be consulted in determining the correct balance of the attic ventilation needs.