How many roof vents do you need? Is there such as thing as too many? You may be surprised to learn that more is not always better.

Attic venting is crucial. There is a tendency however to add more roof vents at the ridge to accomplish this. It seems intuitive that this might work, except that in order for good venting to occur you need convection to occur. So, to encourage this you need more venting lower down on the roof (and preferably at the soffit area) in order to draw in cooler air. This then forces the hotter attic area out the roof vents at the ridge area. With more venting at the ridge versus the soffit area, good venting may not occur.

There are some general rules of thumb for venting an attic space:

• There should be one square foot (1 sq. ft.) of vent space for every 600 sq. ft. of attic area
• Approximately 60% of your venting should be at the soffit area overhanging the house.

Without convection occurring you can trap air & inhibit good venting, which can promote condensation, frost in winter, wood rot and mould growth in your attic.

If you are thinking of installing turbine vents (sometimes called whirlybirds), we don’t recommend them as a general rule.

So…how is your attic venting?