Insulating Concrete foundation walls

Reply

  #1  
Old 03-03-19, 10:23 AM
B
Member
Thread Starter
Join Date: Mar 2019
Posts: 4
Received 0 Votes on 0 Posts
Insulating Concrete foundation walls

Hi everyone,
Preparing to finish my basement, and came across an insulating issue. The basement is all concrete, with 1" rigid foam already on the walls, then a concrete and wood 'stud' every 24". I have an open French drain around the perimeter of the entire floor, which will be behind the framing once its completed. I started using faced fiberglass along one wall but then got concerned about moisture that may come up from the ground and/or from the French drain, which stays MOSTLY dry but has a few areas that gets some water. Here are some possibilities I came up with, but am looking for guidance-
Am I safe to stay with the faced fiberglass? I could install return grills around the basement to allow the inside of the walls to breathe?
Should I change the type of insulation I'm using to rigid board or unfaced?
Should I insulate the framed walls I will be building instead of the foundation walls?
Thanks in advance!
 
Sponsored Links
  #2  
Old 03-03-19, 10:44 AM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 26,221
Received 721 Votes on 667 Posts
2" of foam would be better than 1". Some places have codes that require foundation foam insulation to be R-10 or better. (see link)

In any case, you will want to tape all the seams on your foam to be sure there is no air leakage. If you can't return the fiberglass, remove the facing. You don't want to use faced insulation below grade. And you don't want grilles, they would do as much harm as good. You want a dead air space behind the wall.

concrete and wood 'stud'
I have never seen a concrete and wood stud. are you referring to some sort of vertical reinforcement? Post a picture if you can.
 
  #3  
Old 03-03-19, 11:16 AM
B
Member
Thread Starter
Join Date: Mar 2019
Posts: 4
Received 0 Votes on 0 Posts
Thanks, I was trying to avoid the rigid foam mainly for cost purposes, but I was afraid that would be the easiest, most effective method.

Here is an example, they arent actual studs, I just worded it that way but didn't describe it very well.
 
Attached Images   
  #4  
Old 03-03-19, 11:21 AM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 26,221
Received 721 Votes on 667 Posts
So the "studs" with the holes in them are concrete? That's a new one. Since it's all stapled up and finished, you probably don't need to worry overly much. Kraft facing isn't the end of the world. Would have been better unfaced, but it is what it is.
 
  #5  
Old 03-03-19, 11:32 AM
B
Member
Thread Starter
Join Date: Mar 2019
Posts: 4
Received 0 Votes on 0 Posts
So you wouldnt be concerned of any moisture getting trapped that comes from the floor or drain? Think I'd be safe if I did the rest of the basement just in unfaced?
 
  #6  
Old 03-03-19, 12:02 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 26,221
Received 721 Votes on 667 Posts
I don't think it's a show stopper, no. Kraft facing is a Class II vapor "retarder"... with a perm of 1. It's not as much of a vapor barrier as 4 mil or 6 mil plastic... which is 10-20x more effective at preventing moisture to pass. I think it will be fine. Millions of houses got finished with kraft faced insulation and most of them are fine as long as they don't have wet foundation walls. Your foam behind will be a big plus, even if it is only 1".

If you want to wait around for Bud9051 to comment, (or you can private message him to get his attention) he knows way more about the whys and wherefores than I do.

Yes, I think you should use unfaced on the rest. And definitely use mold resistant drywall. Its best for basements and bathrooms.
 
  #7  
Old 03-03-19, 01:25 PM
Marq1's Avatar
Member
Join Date: Sep 2016
Location: USA MI
Posts: 6,710
Received 396 Votes on 370 Posts
Kraft facing isn't the end of the world.
Just cut some vertical slits in the paper, tada, unfaced insulation!!
 
  #8  
Old 03-04-19, 03:49 PM
B
Member
Thread Starter
Join Date: Mar 2019
Posts: 4
Received 0 Votes on 0 Posts
"most of them are fine as long as they don't have wet foundation walls"

Ok, so any moisture from the concrete on the floor wouldnt pose a problem down the line, of I remove or slice some of the facing on what is already done and do the remainder of the basement in unfaced? Really appreciate your responses, I'm trying to do this right to avoid potential catastrophes down the line
 
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: