Gable Vents

Rectangular or triangular vents in the gables at the ends of an attic are essentially exit holes for hot or moist air passing out of a house near the peak of the roof. Since a triangular vent can be located nearer the very peak of the roof, where the hottest air concentrates, it's the more efficient of the two shapes. Get a model pitched at the same angle as your roof (some are adjustable). A rectangular vent is somewhat easier to install, and many homeowners prefer it for that reason.

To install either type, cut through the siding of the house, the sheathing behind it and —probably—part of a stud. These cuts are easily made with a saber saw, and the installation of one or more 2-by-4 horizontal bracing beams called headers (below) will leave the wall even stronger than before. Caulk with roofing cement all around the new vent to make a rain-tight seal.

A Rectangular Opening (graphic 1, graphic 2)

1. Cutting a vent hole. Locate the vent as close to the peak of the roof as possible, but leave enough space above the vent hole for headers (Step 2). Inside the attic, mark cutting lines on the attic wall for a rectangle 1/4 inch larger than the part of the vent that will fit into the wall. Drill holes through the wall at the corners of the marked tangle as starting points for a saber or keyhole saw, and cut through the sheathing and siding. You may have to remove a section of a stud; if so, cut away 1 1/2 inches of the stud above and below the vent hole, to allow for headers.

2. Installing headers. Cut two pieces of 2-by-4 long enough to fit between the uncut studs at the left and right of the vent hole. These headers will make a frame for the upper and lower edges of the hole. Fasten them in position with nails driven horizontally through the uncut studs into the end of each header, and then vertically through the center of each header into the end of the cut stud above and below.

3. Putting in the vent. Working outside the house, apply caulking to the outer flange of the vent and set the vent into the hole you have cut, with the vent louvers angled down. Have a helper hold the vent in place if necessary and , working inside the house, fasten the vent to the headers with nails driven through the inner flange of the vent.

If nail holes are provided in the outer flange, from the outside of the house, nail the vent to the siding with aluminum or brass nails.

Caulk the outer edge of the vent flange as you would caulk the edge of a door or window but use roofing cement. Since the outer vent flange will not fit flush against clapboard siding, fill the spaces between the flange and the siding with generous amounts of rooting cement.

A Triangular Opening

1. Cutting a hole. Inside the attic, mark cutting lines to match the part of the vent that will fit through the wall; the peak of the marked tri angle should be just below the bottom of the ridge beam. Drill starter holes at the corners of the triangle and use a saw to cut out the outlined hole. You will probably have to cut through at least one stud; cut away 1½ inches of the stud below the opening to allow for a 2-by-4 header.

2. Installing a single header. Cut a length of 2-by-4 lumber as a header between the uncut studs at the base of the vent hole. Fasten the header in position as you would the lower header for a rectangular vent (Step 2). Cut two more 2-by-4 lengths and attach them to the bottom edges of the rafters above the hole as shown.

3. Putting in the vent. Apply roofing cement to the outer vent flange, fit the vent into position in the wall, and nail the inner vent flange to the rafters and the header. If nail holes are provided in the outer flange, nail it to the sheathing. With the vent in place, caulk all around the edge of the outer flange with roofing cement as de scribed for a rectangular vent.