Effective roof ventilation lets you cut your air-conditioning bill by 30 percent and helps your roof shingles last longer, too. A key part of any ventilation strategy is a ridge vent, which exhausts hot air from the highest point in your attic without help from fans or blowers. All it needs is a balanced amount of fresh air entering the attic, usually through soffit vents (also called under-eave vents), gable vents or both.

Ridge vents adjust to different roof pitches and come in painted metal typically aluminum and plastic versions. Although metal vents have been around longer, homeowners and contractors now prefer plastic vents like the Builder's Edge series sold here at CornerHardware.com. Unlike their metal counterparts, plastic ridge vents don't dent, and they can be capped with shingles to blend with the rest of the roof. (Most metal vents can't be capped.)

TOOLS AND MATERIALS-7 1/4-inch circular saw-Plastic ridge vent-Remodeling blade-Mineral spirits-Chalk line-New cap shingles-Tape measure-Nails-Flat bar-Polyurethane sealant-Claw hammer

Step by Step
 
1. Remove the old cap shingles. These are the shingles that cover the roof peak, and they're installed with roofing nails and/or roof cement. Remove them with a claw hammer and a flat bar. You won't be able to reuse the shingles, but it's less messy if you remove them intact instead of in small pieces.

You can also expect the blade to get gummed up, especially in the case of asphalt shingles. If the shingle residue starts to impede your progress, unplug the saw and clean the blade with a rag dipped in mineral spirits. Pros and experienced DIYers using powerful saws adjust the blade depth to cut through the shingles and sheathing all at once, just skimming the rafter tops. If your roof has thick sheathing and multiple layers of shingles, make a first cut through the shingles only and a second cut through the sheathing.

Follow the lines you marked, but stop the cuts 12 inches from each gable end, chimney or intersecting hip roof. Your circular saw won't be able to cut all the way up to vertical obstructions, and you want to avoid cutting into any of the crucial framing at the ends of your roof. As you're sawing, be careful to not cut into the rafter tops. Finally, use a sharp chisel to chop through the last 12 inches of sheathing at the end of each cut. This will leave you with a pair of long, narrow openings on either side of the ridge board.

4. Nail the ridge vent in place. Vent sections are designed to interlock and can also be cut to length. Use a crosscut saw or a circular saw to cut plastic vents and tin snips to cut metal vents. Though most vents fit a wide range of roof pitches, you'll find that flexing a plastic vent back and forth a few times will make it adjust more easily to your roof. Fasten each vent section over the peak, using the nails recommended by the manufacturer. When cutting and joining sections, keep the layered baffle material intact inside the vent; it keeps out insects and driving rain and snow. For the best appearance, run your vent all the way to the end of the ridge. Where the ridge is interrupted by a chimney or other obstruction, butt the vent up against the vertical surface and seal the intersection with roofing cement or polyurethane sealant. Cover the joint with flashing.

5. Install cap shingles. You can buy cap shingles as precut squares or make your own by cutting square sections from standard shingles. Begin at the end of the roof that faces away from prevailing winds. Start off with a double cap layer bedded in roof cement. Overlap each succeeding cap by half (with asphalt shingles, expose only rough-particle-covered part of the shingle). Now that your roof can breathe easier, so can you.

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