Step 1 – Use a tape measure to calculate the dimensions of the attic. If your attic spans the entire area of your house then it will be easier for you to measure the outside of your house. Let’s assume that your attic floor has an area of 1200 sq ft (30×40 ft).
Step 2 – In order to find the appropriate venting needs of your attic, you’ll need to divide 1200 (floor area) by 150. The answer will give you your roof’s venting needs.
Step 3 – Your next step is to measure your roof ridge’s length. Multiply the length by 18 square inches. The answer is the amount of venting for a ridge provider per linear foot.
Step 4 – Calculate the dimensions of the soffit vents and then measure their areas. Make sure you have sufficient numbers in order to have extra venting for your attic. You can usually find the square footage of a soffit vent on the label.
For example, if you use a 6×12 rectangular vent then it means you’ll need 10 of those since each one has around ½ square foot and you have to match it with the ridge vents.
Step 5 — Next, use a ruler and marking pencil to measure and mark those dimensions out onto the roof.
Step 6 — Use a jigsaw or reciprocating saw to cut along your measurements. Make sure to cut through shingles and wood underneath.
Step 7 – Next, use a pry bar to loosen shingles and remove the section.
Step 8 – Apply a thick layer of caulk to the flange of the vent (the bottom)
Step 9 – After that, slide the vent into the surrounding shingles. The bottom part of the vent should be left exposed. Rest it on the shingles below.
Step 10 — Hammer in nails every few inches to make sure the vent is secure
Step 11 — make sure there are no loose shingles around the vent. If there are, hammer them down with some nails.