Insulated attic rafters, now moisture problem


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Old 04-05-15, 02:42 PM
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Insulated attic rafters, now moisture problem

I am in the process of finishing an attic space. I insulated between 6" rafters with faced insulation. I now have moisture collecting in the peak area. What to do now?? Thanks
 
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Old 04-05-15, 02:51 PM
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If you are going to insulate the rafters, what we refer to as a "hot roof" as opposed to a traditionally vented roof, there are strict guidelines you MUST follow. Placing air permeable insulation against the bottom of the roof where warm humid air can pass through it is a guarantee you will have condensation problems.

What is up there now, just the insulation? Any drywall? Any ventilation?

Bud
 
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Old 04-05-15, 03:46 PM
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Soffit vents?
Is there a ridge vent?
What type roofing do you have?
What do you have for roof vents?
What R value of insulation did you use?
Any baffles installed?
 
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Old 04-05-15, 04:28 PM
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There is just the insulation up now. I do not have a ridge vent yet, but there is two windows that I left cracked open for cross ventilation. The roof is shingles, and between the rafters and plywood there are 1" nailers left over from slate roof. I had hoped this would allow for enough ventilation when I get the ridge vent in. So,
....No baffles but 1" nailers between rafters and plywood roof sheating

.....6" faced insulation between rafters

....No ridge vent yet, but do have cross ventilation for now with windows cracked.

So what is best way to make this right.
 
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Old 04-05-15, 05:28 PM
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BTW fuzzy, welcome to the forum,
When you insulate the slopes and choose to ventilate above the insulation, you need intake vents down low, typically in the soffits (if you have soffits) and a clear air path all the way to the ridge vent. In a 2x6 rafter, a 1.5" air gap leaves insufficient space for insulation.

If you use fiberglass insulation with the ventilation air flowing above it, the resulting insulation value is well below the rating on the package.

Here is a link on vaulted ceiling insulation requirements with some illustrations. Check your local code department for your specific requirements.
http://www.cbs.state.or.us/bcd/progr...s/ResPub_8.pdf

Bud
 
  #6  
Old 04-06-15, 04:52 AM
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Take it all back down.
Add 2 X 2's to the bottom of the rafters, install baffles, then the insulation.
Vapor barrier then sheet rock.
There's no way to get the needed air flow along the roof to the ridge without adding the baffles.
If this is going to be a bedroom you also should have gotten a permit, must have an egress window, outlets every 6'.
100% sure this area was even designed for living space? What size and what's the free spans of the floor joists?
 
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Old 04-06-15, 10:04 AM
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I added new floor joists, 10" on 16ctr, with a 14'span
I can add the soffit vents.
I will have a 14' wide dormer installed this summer
The insulation will have to be redone I see.
Thanks for all replies

Great forum
 
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Old 04-06-15, 12:21 PM
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