9 Things to Know about Roof Ventilation

Roof Ventilation
By: Terrance F Quinn

1. Venting your attic/roof is the best and most cost effective way to reduce the heat and moisture build up in your attic and cut down on the possibility of ice dams in the winter.

2. Moisture in your attic can be caused by the use of washing machines, dish washers, bath tubs, showers, and tumble driers unless these items are properly ventilated through the roof. In some cases the condensation can be bad enough to be mistaken for a roof leak.

3. Lack of Roof ventilation is the leading cause of roof rot and structure failure. Moisture travels up and settles on the cold roof boards in the winter to form frost, and penetrates the sheathing in summer to cause mold, mildew, condensation, curling shingles, buckled sheathing, and structural failures.

4. Ice Dams – ice dams are the result of melting snow continually refreezing at the roof perimeter and then backing up under the shingles and causing leaks. Proper ventilation used in conjunction with heavy insulation and an air barrier can create a Cold Roof Assembly which will help eliminate ice dams.

5. The most permanent way to stop this problem is with adequate ventilation.  Both soffit vents and ridge vents are needed.   This combination will create a “chimney effect” causing the cooler air entering the attic from the bottom or soffits to heat up and rise out the ridge vents at the top taking the moist humid air with it.

5.  Most attics are under insulated and improperly insulated.  The soffits should be free to allow air flow from the outside pass the insulation, this is usually done with baffles placed at the outside edge of the overhangs (soffits) and running up3 to 6feet along the roof rafters to reach an area above the insulation.   If an attic is insulated along the rafters, an air space should be constructed along the rafters to allow for this air flow.

solar roof vent

6. Also available are electric or solar powered roof fans that take the air out and work like an exhaust fan in your kitchen taking the steam or humid air with them.

7. Roof vents can be installed on any slop or style of roof, in either exhaust or intake form.

8. Proper installation of vents and insulation should result in the attic space being about the same temperature as the outside of the house.  This will help prevent heat build up in the summer and ice dams in the winter.

9. Every new roof installation should include proper ventilation, and it’s required by the current Massachusetts building codes.