What is the purpose of roof ventilation?
The simple answer is to let the heat out of your attic, but that’s not the whole story. An effective ventilation system (notice I said system there. I’ll explain later…) reduces the amount of heat in the summer and moisture in the winter in your attic space. It helps to make your heating and cooling systems more efficient. This, in effect, helps increase the life of your roof too.
Now let’s talk about the “system”. Roof vents, (exhaust), let the air out of your attic, but that air has to be replaced. You want it to be replaced with cooler air, but where does that air come from? In addition to exhaust vents, you need intake vents. The coolest air anywhere around your house is usually under the overhangs, because it is always shaded. That’s why the best place for intake ventilation is the soffit. Vented vinyl or aluminum soffit is an easy way to allow cooler air into your attic to replace the hot air exiting through the roof vents.
Generally, you should have at least the same amount of intake as you have exhaust. A good rule of thumb is to have 1 square foot of ventilation for every 150 square feet of attic space; half should be intake and half exhaust.
Following these guidelines is important to the life of your roof and for your wallet in the long run. A few indicators that you may not be getting adequate ventilation are if you notice the following:
- Excessive heat in the attic during the summer months
- Mold growth
- Frost on sheathing, rafters or other items in the attic
- Water dripping from tips of nails (not necessarily due to a roof leak)
If you are experiencing any of these issues, you may have a ventilation issue and should have your roof evaluated by a qualified roofing company. Feel free to our main office at 314-596-0596 should you have need of our services.