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PCinCT 01-18-2012 02:36 PM

Attic Ventilation Issue After New Roof
 
We just had a new roof put on our 25 year-old colonial house, including a new ridge vent (Shingle Vent II). Attic is finished, with two access doors in kneewall on one side or room. While putting away Christmas decorations behind the kneewall, we discovered lots of moisture on the roof sheathing behind kneewall, and drips from nail heads onto attic subflooring. Never seen this before....After getting the roofer out to inspect, he said we need soffit vents installed to allow correct ventilation of roof, and to prevent heated air from being drawn into the unheated spaxce behind the kneewall (which is insulated). The previous owners had the attic finished, and the contractor did install stryrofoam proper vent behind the ceiling insulation, but it appears crushed, so not sure if I should proceed with installing soffit vents (was going to use 3 inch round), since there may not be adequate air flow behind the insulation up to the ridge vent.

Shouldn't the roofing contractor have informed us of the fact that without soffit vents, the ridge vent they were installing would not function properly?

How should I proceed to improve ventilation in my attic?

I also need to add insulation around the access doors in the kneewall and around some of the heating ducts hat feed the upstairs bedrooms which are visible and not fully insulated in the floor behind the kneewall in attic, to decrease air/heat flow into the uncondiitoned space behind kneewall.

Thanks,
PCinCT

joecaption 01-18-2012 02:49 PM

http://www.icc-es.org/reports/pdf_files/BNBC/97-22.pdf
A ridge vent is pretty useless without a soffit vent.
Did they install Storm and Ice shield at the bottom of the roof?
With out see what you have now it's hard to make suggestions, also we have no idea where your located.
Having uninsulated heating ducts in an unheated space is a great way for condinsation to form.

PCinCT 01-18-2012 03:08 PM

Quote:

Originally Posted by joecaption (Post 826900)
http://www.icc-es.org/reports/pdf_files/BNBC/97-22.pdf
A ridge vent is pretty useless without a soffit vent.
Did they install Storm and Ice shield at the bottom of the roof?
With out see what you have now it's hard to make suggestions, also we have no idea where your located.
Having uninsulated heating ducts in an unheated space is a great way for condinsation to form.

Thanks for your reply - I am located in coastal CT.
Yes, they installed 36 inches of Ice and Water shield at the bottom of the roof. I can take pictures and post if that would help (I am new to this site, so may need some help on how to post photos).
PCinCT

Gary in WA 01-18-2012 07:16 PM

Here you go: http://www.diychatroom.com/f98/

#3, and 4 down the list.......

"Having uninsulated heating ducts in an unheated space is a great way for condinsation to form."----- I think Joe hit the nail on the head, check for attic access door weatherstripping also.

Gary

Windows on Wash 01-18-2012 10:40 PM

Picture from outside would help as well.

Is there an overhang and enough for soffits?

jmiller 01-19-2012 09:50 AM

Quote:

Originally Posted by PCinCT (Post 826886)
We just had a new roof put on our 25 year-old colonial house, including a new ridge vent (Shingle Vent II). Attic is finished, with two access doors in kneewall on one side or room. While putting away Christmas decorations behind the kneewall, we discovered lots of moisture on the roof sheathing behind kneewall, and drips from nail heads onto attic subflooring. Never seen this before....

If you didn't notice until the vent was installed, I'm guessing there is in fact an air space above the insulation, and the new vent is pulling more conditioned air through your access hatches which is causing the condensation.

Quote:

After getting the roofer out to inspect, he said we need soffit vents installed to allow correct ventilation of roof, and to prevent heated air from being drawn into the unheated spaxce behind the kneewall (which is insulated). The previous owners had the attic finished, and the contractor did install stryrofoam proper vent behind the ceiling insulation, but it appears crushed, so not sure if I should proceed with installing soffit vents (was going to use 3 inch round), since there may not be adequate air flow behind the insulation up to the ridge vent.
What size are your roof rafters, and what R value of batt insulation is stuffed in there?

Quote:

Shouldn't the roofing contractor have informed us of the fact that without soffit vents, the ridge vent they were installing would not function properly?
One would think, but it's not a fun job and nowhere as easy as cutting a slot and installing SVii. If you're thinking legal recourse, unless it was addressed in the contract I doubt you have a leg to stand on. You could, of course, not hire him again (I wouldn't).

Quote:

How should I proceed to improve ventilation in my attic?
Adding soffit vents can only help. A few 3" round ones here and there will do next to nothing for intake though. With SVii you have , IIRC, around 18" of net free area exhaust per linear foot. That would be 9 square inches per linear foot you'd need on both eaves, or in terms of round vents, three or four vents every foot. :no:

Quote:

I also need to add insulation around the access doors in the kneewall and around some of the heating ducts hat feed the upstairs bedrooms which are visible and not fully insulated in the floor behind the kneewall in attic, to decrease air/heat flow into the uncondiitoned space behind kneewall.
Yes, you do. Glue a couple layers of rigid insulation to the back of the access door, install weather stripping where the door meets the jamb, and make sure it's tight when secure.


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