New insulation wet?


  #1  
Old 05-18-12, 12:28 PM
B
Member
Thread Starter
Join Date: May 2012
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
New insulation wet?

So I had my 80 year old house insulated a year ago - blown into the walls on the lower levels and rolls of insulation between the joists in the attic because I'm planning on finishing the space. The attic insulation was then covered with a sheet of plastic. Since it has warmed up this year, an enormous amount of condensation has formed on the inside of the plastic in about 3/4 of the space and it feels very humid in there. The same thing happened last year and the contractor came out and replaced half the insulation, thinking they maybe put damp insulation in there to begin with. Any ideas on what could be causing this and what can be done to remediate it before I develop a mold problem in there??? (Roof is not leaking...)
 
  #2  
Old 05-18-12, 12:41 PM
S
Group Moderator
Join Date: Oct 2004
Location: WI/MN
Posts: 19,125
Received 1,263 Upvotes on 1,204 Posts
Welcome to the forums.

The plastic is on top of the insulation? The moisture is coming up from within your house and the plastic is trapping it there.
 
  #3  
Old 05-18-12, 02:40 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 36,607
Upvotes: 0
Received 9 Upvotes on 8 Posts
As Mitch said, your vapor barrier should have been below the insulation. Having it above creates a "pot lid" that will trap condensation. Get rid of the plastic.
 
  #4  
Old 05-18-12, 02:48 PM
S
Group Moderator
Join Date: Oct 2004
Location: WI/MN
Posts: 19,125
Received 1,263 Upvotes on 1,204 Posts
Actually, given that you plan to finish this space, I think you ultimately want the insulation above the attic, not in the floor.
 
  #5  
Old 05-18-12, 05:19 PM
B
Member
Thread Starter
Join Date: May 2012
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
Let me clarify - the condensation is on the inside of the plastic - between the insulation and the plastic barrier they covered it with. And it is on the ceiling of the attic - I probably used the wrong terminology. Definitely not anything close to a professional!
 
  #6  
Old 05-18-12, 05:24 PM
B
Member
Thread Starter
Join Date: May 2012
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
I'll try taking it down and hope it dries out fairly quickly. Thank you for your quick reply....
 
  #7  
Old 05-18-12, 05:42 PM
D
Member
Join Date: Aug 2009
Location: USA
Posts: 4,344
Upvotes: 0
Received 1 Upvote on 1 Post
They are not called joists, they are called rafters.

I think the question now is how deep are your rafters and how deep is your insulation? In your installation, there should be a gap between the insulation and the roof deck to allow ventilation from vents in the soffit to vents at the peak of the roof.

I am going to make an assumption based on the age of your house. I don't think your rafters are very deep at all and the insulation was possibly installed against the roof deck. If that is the case, then I am pretty sure that is your problem. Especially if you have vents in your soffits and at the ridge that would allow moist air to flow between the rafters during the day, then when things cool off at night, it condenses onto the plastic.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: