venting finished attic that has no space between insulation and roof

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  #1  
Old 06-18-04, 05:16 AM
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venting finished attic that has no space between insulation and roof

Hello all. I hope someone can help us (and the 2 contractors who have diagnosed the problem as "nothin' to do now"). The previous owners of our house finished the attic and put in absolutely no ventilation. We have been told that we cannot put in ventilation now because there is no space left between the insulation and the roof. Please help us! --Broiling in Pennsylvania (:
 
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Old 06-18-04, 07:59 AM
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You dont say what you have there. Can you vent some behind the knee walls ? Can you slide foam rafter vents over the insulation?


ED
 
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Old 06-18-04, 11:01 AM
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You dont say what you have there. Can you vent some behind the knee walls ? Can you slide foam rafter vents over the insulation?

"knee walls"? Are "knee walls" the short walls along the sides where a short wall was framed away from the slope of the roof. If this is correct.... The attic was finished so that the side walls of the attic are framed about 4' out from the actual meeting of the roof with the side of the house. Each of these walls has access doors to get into this 4' deep space for storage etc. Within these storage eaves they did not sheetrock the roof/attic ceiling. In here, you can see the insulation. The insulation goes from the point where the roof and wall meet and goes up, presumably all the way to the ridge of the roof, although one cannot see this because it is sheetrocked. How would you vent these knee walls?

Can you slide foam rafter vents over the insulation?
By "over the insulation" do you mean on the interior side of the insulation. (sorry, i'm such a dunce at this) If so, we could slide foam rafter vents on the underside/inside view of the insulation...up to a certain point (that point where the "knee wall" (?) is built...after that point, everything is sheetrocked. Where would the foam rafter vents empty? Would these do good if we would only be connecting the foam vent to the several feet of exposed ceiling/roof to the soffets?

Thanks so much for your time. It's nice to know that there might be something we can do!
Amy
 
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Old 06-21-04, 05:01 PM
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yes, those spaces behind the short walls are knee walls. vent those spaces.


as for the space you refer to above the knee wall, if it is only sheetrock, insulation, plywood then shingles, it does not look good for venting. i would recommend a ridge vent, allowing these spaces to breathe, trying to slide foam pieces into the space after the insulation is in place is probably not going to be feasible unless you have the room. how big is the rafter?
 
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Old 06-22-04, 06:27 AM
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reply from Pennsylvania

First, thanks so much for your time!

Yes, unfortunately, it does appear that it is sheetrock, insulation, plywood, roof shingles in most of attic, except behind knee walls. Behind knee walls is same, minus the sheetrock.

RE: Venting knee walls -- do you mean to take down the exposed insulation, insert venting material to connect with vents to be cut into soffets, reinsert insulation?

RE: Ridge Vent -- install ridge vent, even though there won't be any air flow space in the majority of attic, i.e., except behind knee walls (which, when I really think about it, is a good amount of space)

Would multiple ridge vents be better and worth the additional expense?

Talk to you soon (because you are so considerately prompt in replying!! Thanks again. I know that it is only to me that this is an ever present problem and thought on my mind. ha ha)

Amy
 
  #6  
Old 06-22-04, 06:59 AM
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An alternative:
We had the same non-vent type problem once, but with a 28'-high A-frame built in 1977.
The A is built of insulated 2X12s on 16" centers with kneewalls from one end to the other upstairs and downstairs. The contractor put in no venting whatsoever, and there was no way to retrofit any venting in the roof or kneewalls of the A-frame.
It always used to be at least 10 degrees+ hotter upstairs (16.5' interior floor-to-ceiling peaks), and the heat and humidity collected in the upper half of the upstairs, ruining the interior paint.
The only solution that I could think of was to dump the heat and humidity out with two strategically placed 7" ceiling-through-roof exhaust fans installed as near the peak as possible. They are both on interior thermostats at exhaust fan level, one set at 75 and the other at 85 for back-up on really hot days. They are only "on" during hot, humid weather, as called for by the tstats. The weather-proof boxed fans have single-louvered exhausts, so that nothing escapes except when running.
It may not be as energy efficient as proper venting, but it works. It is just as cool upstairs as down now, and there is no heat and humidity problem upstairs anymore.
Good Luck!
Mike
 
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Old 06-22-04, 11:59 AM
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Thanks Mike!

Mike,
Thanks for taking the time to post your experience w/ the A Frame. That idea definitely solves one of our 2 problems--the HOT HOT HOT upstairs. Question: do you know if these fans you had in the A Frame also benefitted the problem of roof life shortened by the lack of venting?
Thanks!!
Amy
 
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Old 06-22-04, 02:29 PM
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Yes, keeping it much cooler (airconditioning) on the interior of the roof (the peaked ceiling inside) certainly contributes to prolonging roof life, probably more than just venting an uncooled, unfinished attic in my opinion.
Dumping the built-up heat and humidity formerly trapped in the upper half of our 16.5' peaked ceiling/roof has made it MUCH cooler upstairs.
(We keep it 68 degrees year-round in our home, primarily due to my wife's breathing problems with high heat and humidity, and also personal preference.)
Any interior AC temp below the outside roof temp circulating within your finished attic should help solve both your problems in lieu of being able to accomplish conventional venting.
It's been so long ago that I've forgotten exactly where I found those 7" boxed louvered exhaust fans, but I think that I found them through www.wwgrainger.com . Depending upon the cubic footage (height X width X depth) of your finished attic, one may be enough for your needs.
Good luck!
Mike
 
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Old 06-22-04, 04:10 PM
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good advice, mike.
 
  #10  
Old 06-22-04, 05:37 PM
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Grainger still has them in a 8" and 10" with backdraft dampers. Look under ceiling fans the 8" is 180 CFM and the 10" is 350 CFM.
They have a 7" Shutter mounted exhaust fan at a 120 CFM


ED
 
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Old 06-22-04, 08:13 PM
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Is this the consensus?

Seems like Ed and HVAC both agree with Mike's exhaust fan solution? Would you guys suggest doing both the exhaust fan(s) and also doing vents to soffets behind the knee walls? I'd rather spare the expense. However, if this is best for the temperature and the roof life, will do.
Thanks all for so much of your time in helping me with this.
Amy
 
  #12  
Old 06-23-04, 02:30 AM
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I would do both if I could, but a ceiling/roof exhaust fan alone will probably solve your problem.
I wired mine where I can unplug them in the winter, but you also could put the tstat(s) on a switch to accomplish the same thing.
I'll let the pros advise you from here (I'm not one...just a DIYer).
Good Luck!
Mike
 
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Old 06-23-04, 08:36 AM
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For the vent fan in the attic attic sq ft X 0.7 == CFM


ED
 
  #14  
Old 06-23-04, 10:10 AM
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A last (I hope) question

Ed
What is "CFM"?

HVAC
RE: Venting knee walls -- do you mean to take down the exposed insulation, insert venting material to connect with vents to be cut into soffets, reinsert insulation?

Thanks to Ed, HVAC, and Mike!!!
I am compiling all of this info. to present to a contractor.
Thanks again,
Amy
 
  #15  
Old 06-23-04, 12:08 PM
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CFM=Cubic Feet per Minute (exhaust fan capacity of air moved).
W.W. Grainger tech support can advise you about which fan will suffice if you give them the dimensions, but IMHO, there is no such thing as "too much' CFM with an exhaust fan. I always go for more CFM than recommended. The faster it dumps the hot humid air, the faster it cools and shuts down.
Mike
 
  #16  
Old 06-09-08, 10:02 AM
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Hey there,

I have same problem, and I want to clarify what solutions you guys are suggesting.

I have a cape cod style house with a full dormer on the back, finsihsed attic into a bathroom, two small (when i say small, I mean small!) bedrooms, and an open space loft with a closet. NO exhaust. the Heat is unbearable up there, even with insulation and white/light shingles.

I want to vent the roof but two contractors said it cannot be done becuase there is no space between the roof and the insulation, or between the rafters and drywall, or whatever. (Meaning, no airflow for venting all rafters)

But my thing is that I want to vent the ROOMS. I mean go right through the roof, insuation, drywall and into the finished space. I cant understand why this would not work, unless perhaps the 'neck' of a fan would not be long enough to go through all the way (I cant imagine that I have more than 8-10inches from shingle to sheetrock -- I have no idea how thick a rafter beam is...).

Anyway, would something like THIS work: http://www.grainger.com/Grainger/items/5C041

I'd install it on the slanted part of roof, not the dormer. Am I nuts? I just could not understand why two contractors have told me the area cannot be vented.

Any suggestions on this would be appreciated, or references to somethign else that could work.

Thank you!
 
  #17  
Old 06-30-09, 07:03 AM
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Roof exhaust fan right through attic living space ceiling.

Ted3478 Iím with you I plan on doing this. Did you end up exhausting right through the attic ceiling living space. Any details how and with what materials you did it with?
 
 

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