Power ventilators replace air (called air exchanges) in the attic. Blowing wind turns the turbine on top of the power ventilator and causes the spinning turbine to suck air out of the attic space. During warmer weather, moisture collects in the home from sources like baths and showers, laundry, washing dishes, and hot tubs. This moisture, if not removed, will migrate into the building structure and cause mold, mildew, and dry rot. Since warm air rises, the moisture typically collects on surfaces in the attic space. A properly vented attic space should have intake ventilation—usually vents installed in the soffits—as well as ventilators installed in the face of the roof or at the ridgeline. In older homes, there may not be enough ventilation to sufficiently ventilate the attic space so you may want to install a power ventilator to move greater amounts of air.
- Plan carefully where you want to install the power ventilator. Typically, they are installed in the upper third of the roof face.
- If your roof is too steep, you may not be able to install a power ventilator at all. In this case, you may want to choose a different type of ventilator.
- Locate the roof joists where you will install the ventilator.
- Mark a location in the center between two roof joists.
- Cut the asphalt shingles to the dimensions of the throat or barrel base of the ventilator.
Install the power ventilator
- Starting at the mid-point of the hole in the roof, loosen the shingles by sliding a pry bar underneath them and working the nails free.
- Apply a good quality roof cement to the base of the power ventilator.
- Slide the power ventilator up under the shingles until the power ventilator is centered over the hole in the roof.
- Fasten the flange of the power ventilator to the roof sheathing with 11/2” roofing nails spaced all around the perimeter of the flange.
- Coat the nail heads and the edge of the flange with roof cement or mastic.
- Lay the shingles back down over the ventilator flange.
If your roof shingles are old, they may break when you attempt to loosen them or lift them up. If possible, wait for a warm, sunny day, or even a hot one, to soften the shingles so you can work on them without damaging them.
Practice all rules of ladder safety. Wear proper clothing for working on a roof: good boots, long pants, gloves, and, if necessary for your particular roof, a safety harness and rope.
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