In the same way you breathe through your nose and mouth a roof breathes through its Intake and Exhaust Ventilation. Your attic is like a big lung. Just like a lung, it requires fresh air circulation or it will suffocate and go bad. A properly functioning attic space will replace old, moist, warm air with fresh outside air rapidly to prevent potentially disastrous issues, such as mold and rot, from occurring in your home.
Good ventilation is often the single most overlooked component of the roof system by most roofers in Calgary. Around 2009 the Alberta Building Code restricted the inspection and correction of ventilation to be identified and addressed by roofing contractors during the reroofing process.
Ensuring good ventilation within an attic space is as simple as ensuring that air can freely flow into an attic and freely flow out. Exhaust vents create suction to draw air out which is then replaced by fresh air from the intake vents, typically installed on soffit areas underneath eaves trough overhangs, around the perimeter of a building.
Older homes typically have plywood soffits installed with rectangle shaped intake vents. Newer homes typically have perforated aluminum soffits installed instead. And virtually every roof system has some sort of exhaust vent installed on the rooftop to let old air out.
A common problem with older homes undergoing renovations to the soffit intake plywood areas, is that soft metal installers will install perforated aluminum soffit on top the old rectangle intake vents. If this is done without allowing for a space or gap between the new perforated soffit metals and the old rectangle intake vents, then air becomes restricted in a bottleneck effect, resulting in an obstructed and ultimately inefficient air flow through your attic. It’s imperative that a gap is left between new metals and old vents or that old plywood be cut out altogether to ensure that air may freely flow into your attic from the outside.
In around 2010, the Alberta Building Code changed in a way that has altered intake ventilation installation procedures forever. Minimum spacing between building envelopes was added to the code to prevent potential fires from jumping from one building to another through intake air ventilation. The minimum spacing now enforced by code is greater than the typical building lot spacing used by new home builders. The result of this is that installing intake ventilation in soffit areas is no longer practical.
The only practical solution to this issue is to install intake events on top of the roof near the eaves trough line. This, of course, creates a new problem: that of air intake blockage due to snow accumulation on top of these vents and that of snow infiltration into the attic space. Although problematic for a healthy attic, his has become a challenge to the Calgary and Alberta marketplace, to which we strive to find a creative and sustainable solution through time, trial and error, and patience.
Not having proper ventilation installed for your attic can cause several problems:
1. Premature shingle deterioration
2. Mould growth in the attic space
3. Paint peeling around the upper perimeter of your house
4. Serious condensation build up during winter time
5. Uncomfortable hot air in the house during summer time
…and as if the above 5 problems were reason enough to ensure proper attic air ventilation, your shingle manufacturers warrantee can even become null and void if proper ventilation is not installed.
You can calculate a rough estimate of ventilation required for your attic by using the following formula and process;
a) multiply the total square footage of your attic space by 144
b) now divide by 2
c) now divide by 300
d) you are left with the ‘net free’ square inch area required for each of your intake ventilation, and your exhaust ventilation.
e) you can now divide by the net free square inch area by the net free area provided by a ventilation product to determine how many vents your roof needs in order to be properly ventilated.