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
My goodness Jay that is one dirty vent. Can't say I've seen one any dirtier. :)
Light hardly made its way through James!
Jay, poke your head up in the attic every decade? Come on.... that's a bit overkill... LOL.
I need those tiny scouts to do that..
While a bit faseeeshus Andrea, my comment did make the point! Scouts would be great attic spybots!
Hi Jay,
Sure it was dirty? :-) Or was it shot with cellulose and left for dead. That is the worst vent I have even seen. I have seen a lot of them over the decades of building and inspecting homes. But never one that bad.
Have a great day in Bristow.
Best, Clint McKie
There were two Clint, both the same. I wondered if at some time during the house's 45 year life span a dryer did not blow directly into the attic (for a bunch of years...).
Bet it was hotter than blue blazes up there. Same as this one last week.
Some genius wanted to warm up the attic in the winter.
Not so good either.
Good morning Jay,
Speaking of bathroom vents; which is easier to clean once in a while or keep replacing when the motor burns out.
Make yourself a great day.
I see that from time to time too Scott. Really smart. Why do they call it a "vent?"
Raymond - the motor will definitely burn out and on older houses that is a problem because the new fans have larger carcasses that don't fit into the older space!
I thought people only checked vents when they were getting ready to sell! I've seen some people I know blocking off their attic vents in an effort to keep stink bugs out. Thye don't realize that they would be better off with the stink bugs!
Once again, your excellent title drew me in Jay. You are the master at that!
Once a stink bug got on the straw of my drink Jeff, and I didn't realize he was there. You know what happened. Bummer I didn't have a gable vent to plug up because I was not better off with the stink bug...
Thanks A&J. We try.
Jay you always seem to make every subject simple and logical, this one is no different.
Jay, great blog. It's an area that for most folks 'out of sight, out of mind'. Here in Florida, attic venting is SOOOO inportant! Thanks!
We try to have fun Chuck!
Norman - it's important everywhere, except when the attic is filled with Icynene.
Jay, out of sight, out of mind. That clogged gable vent has been out of sight a long time.
Jay, Another great post, If I wasn't already following you, I would subscribe again. Thanks for sharing.
Good post and you can have a home or it can have you...
So you're saying you broke a sweat up there? Maybe the Billy Jays vent cleaning service should be called!
I really appreciate your posts. I would rather read post here from inspectors and mortgage bankers than anything because the content is so valuable. This is a new one for me and after 24 years in the business it is great for an old dog to learn new tricks.
Clever title for your blog. Thanks for sharing the good information with us.
Betty
Enjoyed reading it Jay. I guess that's where all the hot air hangs out.
I think most people forget that their attic even still exists. It's not a fun place to hang out but you should still check it out.
Jay, a great reminder and a great informative blog as usual. I love the way you word things but Jay, you are not Shakespear, but a very food inspector.
I never thought a vent like that would get cloged but the dust we get it stands to reason they would need to be cleaned.
That is disgusting. I don't have an attic, but I routinely clean the vents in my bathrooms.
Wow! I haven't seen any vents that dirty. Good catch man.
Love the title of your post. It really sucked me in. Love the images you used as well. Really gets your point across. Thanks for venting/sharing.
Jay -- that is a very congested vent. Amazing that it could get that solidly filled and still build up depth.
Mike - a place few venture, unless they store stuff up there.
Thanks Brian. Glad you're on board!
Richie - this is the home having its way, for sure!
Fred - I came down with a different color shirt, and appreciating how cool and comfy 90 degree temps are!
See the vent Joe, see the vent! Good Joe. New tricks are always good!
Thank you Betty. Stop by again!
Pass away Gay. It's useful info!
It does Richard, except when I am talking.
It pays to look from time to time Marc. And if you want to hang, do it early in the morning!
Who could be Shakespeare Jimmy? Not I, forsooth.
David - over time all things get dirty!
That is something some people never pay attention to Suzanne.
Juan - not hard to see, once you Tarzan swing over that far.
Dana - sometimes you have to vent. I know I do!
Steven - indicating I guess that the particles there are very small.
Jay,
Thanks for the information. I was very pleased to learn about this issue that most people don't talk about and it's hard to understand what you don't know. I really like how you explain things.
Thanks again!
I've been saying that for a while Corinne, but few will see any benefit in having a home inspector over.
Patricia - instruction is the key to learning! I hope this post helps.
It is always a treat to read your blog posts. Very informative, and I can never finish them without at least one giggle. Thanks!
Jay, this post makes me want to go check out the garage vent right now-- dirt be gone!
Love learning new things from Active Rain blog posts! I'm passing it on to home owner friends.
Thanks Trisha. You look to be giggling now!
Clean or replace them every month Rosie! Glad you enjoyed this one!
Gotta see it to know Ralph!
Pass away Paul. It's info to benefit others.