Go Back  DoItYourself.com Community Forums > Interior Improvement Center > Basements, Attics and Crawl Spaces
Reload this Page >

Plastic Vapor barrier in attic prior to blown insulation

Plastic Vapor barrier in attic prior to blown insulation


Old 01-26-14, 09:25 AM
Thread Starter
Join Date: Jan 2014
Location: USA
Posts: 5
Received 0 Votes on 0 Posts
Plastic Vapor barrier in attic prior to blown insulation

I am going to blow insulation into my attic and noticed one video where the people put down plastic over the floor studs as a vapor barrier prior to blowing the insulation.

I have only seen this in 1 video of about 10, should I do this ? is it needed or provide benefit?

Sponsored Links
Old 01-26-14, 10:09 AM
Join Date: Oct 2008
Location: New England
Posts: 10,406
Received 23 Votes on 21 Posts
In extremely cold climates, which I think you qualify, a vapor barrier or class I vapor retarder is recommended on the warm side of the insulation. But installing one properly after the sheetrock is up is difficult if not impossible. As al alternative, a good layer of paint can do part of the job and air sealing the house to attic even more so. Air leaks transport much more moisture than vapor diffusion, so recessed lights, electrical boxes, plumbing and wire penetrations and a chimney chase can be worthwhile projects.

Also, make sure bath and kitchen fans are vented fully to the outside, not just into or below a soffit.

Here is a link on vapor barriers: Vapor Barriers or Vapor Diffusion Retarders | Department of Energy

Old 01-26-14, 12:16 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 23,139
Received 195 Votes on 181 Posts
If I understand you correctly, you are wanting to put a poly vapor barrier over the top of your ceiling joists, on top of any existing insulation, and then add more insulation on top of that? IMO that would be a bad idea, as moisture could possibly condense inside the insulation that is below the poly... especially on the colder perimeters of the home.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

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