mold behind insulation

Reply

  #1  
Old 04-18-16, 10:40 AM
W
Member
Thread Starter
Join Date: Apr 2016
Posts: 2
Received 0 Votes on 0 Posts
mold behind insulation

I am sure this has been asked several times in many different ways, but i didn't see anything specific to my situation.

I have a 3 year old home with an unfinished daylight basement in Nebraska. The builder 2x4 framed the outer walls and installed bat insulation in cavities. I noticed that there was black mold and moisture behind the insulation on wall and rim joists in the areas that are above grade. (pictures attached).

I am now finishing my basementName:  20150514_195031.jpg
Views: 1378
Size:  26.5 KBName:  20150516_153404 (1).jpg
Views: 2801
Size:  25.0 KB and will be ready to put drywall up soon. How do I prevent this moisture from occurring, do I need to install a vapor barrier in front of the insulation?
 
Sponsored Links
  #2  
Old 04-18-16, 11:05 AM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,523
Received 37 Votes on 34 Posts
The above grade area is cold in winter and humid air passes through the insulation depositing condensation to form the mold. Moisture also comes up from the footings below and if trapped by a vapor barrier you again get mold.

The current best practice is to cover the concrete walls with a layer of rigid insulation, location dependent as to thickness. Then your stud wall with pressure treated wood at the bottom or anywhere it contacts the concrete. Fill the stud cavities with one of the fiber insulation materials (less expensive). Your total r-value needs to meet your local code requirements. Link below for 09 energy codes but you must check to see what your local authority has adopted.

Bud

Understanding Basements | Building Science Corporation

https://energycode.pnl.gov/EnergyCodeReqs/.
 
  #3  
Old 04-18-16, 11:31 AM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 26,221
Received 721 Votes on 667 Posts
The mold likely came from there being no air barrier (in your insulated but unfinished basement) over the fiberglass. Warm moist air passing through the fiberglass was able to condense on the cold cement wall. If you would have had drywall up over the fiberglass, this probably would not have happened.

I agree with Bud's comments about insulating the exterior concrete wall with 2" rigid insulation, tape seams to prevent air infiltration, then stud walls and additional insulation (with no vapor barrier), followed by drywall and latex paint as a class III vapor retarder.

Since its too late to put 2" foam on the walls (this would be done before walls are framed) you could look into having your walls professionally spray foamed... that would give you the absolute best insulation and air sealing.
 
  #4  
Old 04-18-16, 02:23 PM
W
Member
Thread Starter
Join Date: Apr 2016
Posts: 2
Received 0 Votes on 0 Posts
Thanks for the reply. I think I will go with the spray foam route to seal everything off. Also, I sprayed biocide mold and scrubbed, but can't completely remove all the black. Will this be fine or do I need to get it completely cleaned?
 
  #5  
Old 04-18-16, 02:57 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 26,221
Received 721 Votes on 667 Posts
Not a problem. Sounds like the biocide would have killed any spores.
 
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: