I was just up in my attic checking on something else and noticed that it was really hot up there. I know, I know, it’s almost 90 degrees outside and of course the attic is hot. But there was no air moving out of the two vents in the roof. The attic is above an air conditioned area about 25’x25′ The roof is around a 4-12 with dark shingles. I can see down to the soffits and there should be air coming from there but it sure don’t feel like it.
Should I feel air flowing out the vents?
Replies
>>But there was no air moving out of the two vents in the roof. .... Should I feel air flowing out the vents?
In most cases you won't.
Try this: enter the attic and move away from the hatch. Come back, You'll likely feel a definite difference in air temp directly above the hatch (especially if you have A/C)
If you do. you'll know the higher vents work, at least.
And yes, it'll likely be 20-25 degrees warmer up their than outside
May your whole life become a response to the truth that you've always been loved, you are loved and you always will be loved" Rob Bell, Nooma, "Bullhorn"
"We Live" http://www.youtube.com/watch?v=7kuBgh0VCqI&mode=related&search
And Annie Ross's "Twisted" http://www.youtube.com/watch?v=8lqivrCIRGo&mode=related&search=
"And yes, it'll likely be 20-25 degrees warmer up their than outside"
I can confirm that it is! I've been using a Fluke 62 Mini IR Thermometer and done a fair amount of readings--a lot in my attic. When its 100ºF the lowest part of the attic (measured off the attic folding ladder) is the same. But, the top of the plenum has been measured as high as 128ºF, and the ridge above (12-13' above the plenum top) was measured at 140ºF.
I've also taken some readings along the ridge to see if temperatures differed at the ridge vents and dead-center between two vents and noticed that the vent temps are typically about what the plunum temp is, but in between vents it is the hottest (140ºF).
Conversely, on the same day that it is 100ºF and as much as 140ºF in the attic, the exterior surfaces of my house can easily be between 108 & 114ºF.
When you want to get the air temp somewhere with the IR meter, use a piece of cardboard or some such, propped up or suspended in the air for 5-10 minutes, then shoot off of it.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Yeah, you generally won't easily feel a draft near the roof vents. You might, if you went up on the roof, be able to feel warm air coming out of the vents, however. And, as suggested, if you go into the attic, shut the hatch for a minute or two, then open it just a crack, you should feel cool air coming through the crack.
Note, however, that if you only have two vents on the roof (and likely only 4-5 in the eaves) you're probably a hair under-vented.
Dan. you don't need to shut the hatch to feel it.
I used to get "trapped" in attics when my buyer would mount my ladder behind me but stay on it and within the 'breeze' rising through the hatch, and I'd be in air 20 degrees or so warmer.
I quickly learned to move back directly over them and drip sweat onto them <G!>
May your whole life become a response to the truth that you've always been loved, you are loved and you always will be loved" Rob Bell, Nooma, "Bullhorn"
"We Live" http://www.youtube.com/watch?v=7kuBgh0VCqI&mode=related&search
And Annie Ross's "Twisted" http://www.youtube.com/watch?v=8lqivrCIRGo&mode=related&search=
Yeah, in most cases that's true. Just covering all the bases, and eliminating the possibility of circular convection through the hatch.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Should I feel air flowing out the vents?
Might, might not--the "book" values for minimum ventilation can translate to very low cfm. Low cfm are occasionally not very "sensible" which makes it tricky to "feel" such things.