is only half of the story. For your attic to ventilate properly and for your roof to not fail early, you also need adequate intake ventilation.
The most common form of intake ventilation for houses is installed during the construction. If you step outside and look up by your gutters and the 1 to 2 feet of overhanging roof (called soffits), you’ll probably notice holes atthe top of the wall. Those are bird blocks. Birds are known to nest in them, and they should have wire mesh
covering to keep them (and other critters) out.
These holes are your intake ventilation. Air flows in them from the outside — then it travels up through the attic to exit the vents along the ridge line.
Sometimes intake vents act as exhaust too. Say there’s a heavy wind blowing in the direction of your bird blocks. This can push the air through the attic to exit the other side of your home’s bird blocks.
Just having bird blocks isn’t enough
If your bird blocks are small — especially if they’re smaller than 1″ in diameter — then chances are they do not intake air as much as they need to. The standard 2″ diameter with 2 or 3 holes per block is almost always enough intake ventilation when enough bird blocks are installed.
However, attic insulation is very commonly installed incorrectly. Or people who have gotten in the attic for one reason or another may have pushed the insulation around, blocking the bird blocks.
Many homes with a good bird block setup still don’t get proper intake ventilation because the insulation blocks them from the inside. To avoid this, baffles should be installed on the bottom side of the trusses or rafters at the bird blocks to create an air space between the bird blocks and the insulation.
What if you don’t have bird blocks?
The first thing you may notice is that your roof is aging quickly. Shingles will curl and plywood will soften. If you get in your attic, it will usually be closer to the temperature of your living space as opposed to the outdoor temperature that it should be.
Newer homes almost always have bird blocks, but some older ones with hand-cut rafters or before government codes addressed ventilation often won’t have intake ventilation (or even soffits).
For these homes, the best course of action is to bypass trying to get intake ventilation through where bird blocks should be. Instead, roofers should install intake vents designed to apply over the roof deck, like GAF Cobra IntakePro.
Some roofers will opt to not install these vents even when needed, at the great detriment to the homeowner. Roof intake vents take expertise of installation and increase the cost of a roof replacement project. But they can be the difference between the roof lasting 50 years or 10 years.
If you’ve noticed you don’t have much (or any) ventilation into your attic along your eave (gutter) line, give us a call. It’s not the easiest problem to fix, and many roofers don’t do it right. But we’ve fixed hundreds of roofs/attics with improper intake ventilation — making sure our clients’ roofs last their full expected lifespan instead of dying early from the shingle deformation and sheathing rot that occurs when intake ventilation isn’t working right.