XPS under joists in crawlspace

Reply

  #1  
Old 07-29-19, 07:12 AM
Member
Thread Starter
Join Date: Feb 2013
Location: Canada
Posts: 22
Received 0 Votes on 0 Posts
XPS under joists in crawlspace

Hi all,

I'm in southern Ontario, near Toronto. I'm working on a job now, a poorly insulated crawl space that we intend to remedy. There is very little insulation right now, and I want to improve it. I want to do the following:

1) Put 1 1/2" XPS under the joists, nailed (or glued) and seams taped, just as you see walls done for new construction
2) Fill the joists up with blow-in or batt insulation
3) Add vapor barrier, if necessary, to the top of the joists, before the subfloor.

A few notes:

a) There is one duct running through the spaces between the joists
b) The joists are only about 6"-8" above grade, however the plan is to lay plastic over the soil to create a conditioned crawlspace.

Does my plan have any issues? I'm concerned about moisture/mold buildup, and I want to ensure this solution doesn't promote the growth of mold.

Thanks, Ivan
 
Sponsored Links
  #2  
Old 07-30-19, 07:12 AM
Group Moderator
Join Date: Oct 2004
Location: WI/MN
Posts: 19,387
Received 57 Votes on 54 Posts
If you're conditioning the crawlspace then you should not insulate the ceiling. That said, laying plastic over the soil does not create a conditioned crawlspace so we may not be on the same page here.
 
  #3  
Old 07-30-19, 08:43 AM
Member
Thread Starter
Join Date: Feb 2013
Location: Canada
Posts: 22
Received 0 Votes on 0 Posts
Perhaps my plan isn't a fully conditioned crawlspace, as some are, but as I understand, having a moisture barrier over the soil is a good idea.

Are there any issues with my plan, as I've written?

Thanks, Ivan
 
  #4  
Old 08-01-19, 05:57 PM
Group Moderator
Join Date: Oct 2004
Location: WI/MN
Posts: 19,387
Received 57 Votes on 54 Posts
OK, here's the idea - you can deal with a crawlspace one of two ways:
1. Open the space to the outside air and seal it off from the house air. In this case, you insulate the ceiling.
2. Seal the space from the outside and open it to the house air. In this case, you insulate the walls.
In either case, you do want a vapor barrier on the ground.
 
Reply

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
 
Ask a Question
Question Title:
Description:
Your question will be posted in: