Roof venting is essential. It moves heat and moisture out. Ideally as much air as goes in can come out. Flow.
Ventilation can take many forms - a passive system like the one pictured to the left.
That is a soffit and ridge venting system, and very effective.
It is pure physics. Air is attracted in, gets hot, rises and is encouraged out.
Ideally, again, as much as gets in also gets out.
Venting can be more aggressive too, with an electric attic fan. When the fan is on it also is very effective.
A more common form of passive venting on an older house might include gable vents.
They are usually large, rectangular vents up near the apex of the roof, and air passively flows from the attic space out through the vents on each side.
It's very passive, but heat can get out.
Well, heat can get out when air can get out!
Can I vent a little bit here?
When air can't flow through the vents they are NOT very effective.
Both gable vents on this house needed a shave and a haircut.
They were nearly entirely clogged with dust!
How effectively can air flow through vents this dusty?
Obviously it can't.
I sometimes see the grills on bathroom vents similarly clogged so much with dust that air cannot get out.
The poor fan is trying to extract air, but can't.
Well, in this attic, which was very hot from the lack of ventilation I might add(!), air, and therefore heat, simply can't move.
Rather than cleaning these, it might be easier simply to replace them with a newer grilled vent. Anything that can air can flow through!
To wax Shakespearean - a vent by any other name moves air just as sweet.
Or something like that.
My recommendation: it isn't a bad idea to pop your head into the attic space once or twice a decade to see how the gable vents are doing! If they are clogged, get up there an clean them! If they are really clogged, replace them! Your roof will really appreciate your allowing the attic space to vent.
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560