September 2026
Most roofs that fail early around here were not installed badly. They cooked. Here is what attic ventilation does, why it decides how long your shingles last, and how to tell if yours is wrong.
Two halves, and both have to work
Ventilation is intake and exhaust. Intake happens low, at the soffit under the eave. Exhaust happens high, at the ridge or through vents near the top. Air comes in cool at the bottom, picks up heat, and leaves at the top.
Ridge vent with blocked soffits has nothing to pull. Both halves have to work.
That only works if both halves exist in roughly balanced amounts. Ridge vent with blocked soffits has nothing to pull, so it does very little. Soffit vents with no exhaust path do not move air either.
This is the most common thing we find wrong, and it is usually not the roofer's fault. Insulation gets added over the years and buries the soffit intake without anybody noticing.
A quick way to gauge your attic: go up on a hot afternoon. If it is dramatically hotter than outside rather than somewhat hotter, air is not moving through it the way it should.
What heat actually does to a shingle
An asphalt shingle is rated on the assumption of a reasonably ventilated roof deck. Trap heat underneath it and the asphalt ages faster, the granule bond weakens, and the shingle becomes brittle years ahead of schedule.
In a Memphis August an unventilated attic gets brutally hot, and that heat sits against the underside of your roof all afternoon. Manufacturers know this, which is why many warranties are conditional on adequate ventilation.
Read that again: a ventilation problem can void the warranty on the roof you paid for.
Look at the underside of the decking while you are there. Dark staining, rust on nail points, or any softness is moisture that has been sitting where it should not.
How to check yours
Go outside and look up under the eave. You should see vented soffit panels, and they should not be painted shut or covered. Then look at the ridge line for a ridge vent, or at gable or box vents near the top.
In the attic on a hot afternoon, notice whether it feels like an oven far beyond the outside temperature, and look for daylight at the soffit line. If insulation is packed against the roof deck at the eaves, your intake is likely blocked.
Frost or damp sheathing in winter is the same problem showing up differently: moisture that cannot escape.
Mixing exhaust types can work against you. Ridge vent plus powered fans plus gable vents can short circuit each other so air cycles between vents instead of drawing from the soffit.
Fixing it is usually cheap
Compared to a roof, ventilation work is inexpensive. Adding soffit vents, clearing blocked intake, installing baffles so insulation cannot smother the eave, and adding ridge vent are all modest jobs.
The right time to do it is during a roof replacement, when the ridge is open anyway. The second best time is now, because every summer it runs hot is life taken off the shingles.
If you are replacing the roof anyway, this is the moment to get it right, because the ridge is open and the cost of doing it then is a fraction of doing it later.
Ventilation and moisture, the winter half
Ventilation is usually discussed as a summer heat issue, and in this climate the moisture side matters just as much. Warm damp air from inside the house rises into the attic, and where it meets cold sheathing it condenses.
That is why some attics show damp or frosted plywood in winter, sometimes mistaken for a roof leak. The water is coming from inside the house, not from the sky.
The fix is the same balanced intake and exhaust, plus sealing the obvious air paths from the living space: gaps around recessed lights, the attic hatch, bath fans that dump into the attic instead of outside.
A bath fan venting into an attic is one of the most common and most damaging things we find, and it is usually a cheap correction.
Questions we get asked
Can I have too much ventilation?
You can have it unbalanced, which causes problems. Too much exhaust with too little intake can pull air from inside the house instead of the soffit.
Do powered attic fans help?
Sometimes, and they can also pull conditioned air out of your house if the attic is not well sealed. Passive balanced ventilation is usually the better first move.
Will this lower my power bill?
It can help, though the bigger benefit is roof life. A cooler attic is a less punishing environment for everything in it.
Does my warranty really depend on this?
Many manufacturer warranties include ventilation requirements. It is worth reading yours.
Can you check it while you are here?
Yes, we look at ventilation on every roof we assess. It is too important to skip.
What to take from this
Ventilation is intake at the soffit plus exhaust at the ridge, and both halves must work.
Trapped heat ages shingles years ahead of their rating.
Blocked soffit intake from added insulation is the most common fault we find.
Ventilation work is cheap relative to a roof, and best done during a replacement.
Get it handled
Jonathan Stephenson answers the phone himself, walks the roof, and gives you a written number. Serving Germantown, TN and the Memphis metro.