Venting the attic space of a house will keep the attic cooler during the day. Allowing the heat to escape through the vents permits the free flow of air throughout the roofing system. This free-flowing air reduces the damage heat can do to a roof by reducing heat build-up in the attic. Installing continuous strip soffit venting is the ideal way to let the roof "breathe," extending the roof's life.
Mark the location in the soffit for the continuous strip vent. Snap two chalk lines 2 inches apart at 2 to 4 inches from the edge of the soffit.
Cut out the soffit, using a circular saw. Set the blade high so it will just cut through the soffit. Do not make deep cuts. Use a hand sabre saw to make the end cuts of the marked area.
Attach the vent to the soffit. Use half-inch screws and a drill and space the screws roughly 12 to 16 inches apart.
Go into the attic and pull any attic insulation away from the new vent track. Nail in one-by-fours with a hammer between the rafters as needed to keep the insulation from falling back into the vent path. Do not leave loose insulation lying near the vent, since it will eventually settle back over the vent and block it, defeating the purpose of installing it.
Create an air flow path for the air from the vent to flow through. Install baffles between the rafters on the underside of the roof decking.
Go to the roof's ridge and remove the existing ridge cap's overlapping shingles and felt. Snap chalk lines 4 inches down from the peak, on each side of the ridge. Saw and remove the roof decking along the chalk lines, using a reciprocating saw. Cut the decking with the blade pointed straight down (plumb cut).
Snap two more chalk lines on each side of the opening to match the width of the new ridge vent you will install. Install the new ridge vent according the manufacturer's instructions.
The two kinds of vents either let air in (inlet vents/soffit vents) or let air out (outlet vents/ridge vents). Not having both is as bad as having neither of the two. Calculate the correct amount of continuous strip soffit vent needed for your house. The formula is square footage multiplied by .48 divided by 17. For example, if square footage of the house is 2,000 square feet, multiply 2,000 times .48 and get 960. Divide 960 by 17 to get 56.4. Round this figure down to 56 linear feet of continuous strip vent needed. Include the same amount, 56 linear feet, of ridge vent to be installed on the ridge line to match the recommended amount of strip vent.
To ensure proper attic air flow, make sure both types of vents are in place and equally sized.