If you are building a new home or if you are re-roofing your home the need for proper ventilation cannot be overstated. Bad ventilation can raise energy costs. It can cause your roof to warp due to moisture buildup which can (depending on where you live) lead to the formation of ice dams in the winter. This can lead to roof leaks, gutter damage and increase your future roof and home maintenance costs.
A roof that is well-vented with the amount of intake and exhaust vents will provide numerous benefits to your home and will save you money on energy bills.
Now that I have your attention… All you need are the measurements of your attic and a calculator. It is really that simple to protect your investment and save money in the future. Here is how!
1. Find your attic square footage, remembering to include your garage if it is attached. Let’s say that our space is 33 feet by 37 feet. All we need to do is multiply the numbers together to find our square footage.
33 x 37 = 1221 square feet.
2. Now that we have our total square footage, simply divide this number by 150. The Federal Housing Administration (FHA) recommends between 1/150 to a 1/300 ratio depending on the age of your home. The FHA building codes over the last 20 years are much stricter making them more airtight. This means that newer homes require more ventilation. For our process, we have a newer home therefore the stricter standard applies.
1221 divided by 150 = 8.14
Therefore, 8.14 is the total square footage of ventilation that will be needed for your home.
3. Convert this to square inches. 8.14 x 144 square inches = 1172.16. This number is the total square inches of ventilation that will be needed on your home. Why? Vents are measured in inches, which makes it easier for us to find our final vent calculation.
4. Lets calculate the intake and exhaust vent percentages. Most experts recommend a 60/40 split. This means 60% for intake vents which are usually around the soffits and eaves of the home. Leaving us 40% for the exhaust vents which are typically found near the roof ridge. For this we will need two calculations using our square inches number of 1172.
1172 x .60 = 703 square inches for intake vents
1172 x .40 = 469 square inches for exhaust vents
5. With these numbers we can now choose the correct types of vents. Remember to do your homework. Make certain that your Contractor if your are building a new home or your Roofing Contractor if your putting a new roof on your home, understands this process and talks to you about it.