Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Insulation

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 11-13-2011, 11:22 PM   #1
Newbie
 
Join Date: Oct 2011
Posts: 12
Share |
Default

foam over batts


I am looking to develope my basement. The exterior walls are framed and insulated. The vapor barrier leaves A LOT to be desired!! I was going to pull all the vb and insulation and just spray foam the concrete walls...now I'm thinking of leaving the R12 insulation and putting 2" foam board over the studs for the vb (ship-lap and taped). Is there any good reson I can't do this? I should end up with about an R30 and 2" of foam works as a vapor barrier...Am I missing something or is this a good idea?

Thanx

Ram Guy is offline   Reply With Quote
Old 11-14-2011, 11:06 AM   #2
Exterior Construction
 
Windows on Wash's Avatar
 
Join Date: Aug 2011
Location: VA, MD, DC
Posts: 6,199
Default

foam over batts


Where is the home located?

Foam applied directly the concrete will be much more effective.

Windows on Wash is offline   Reply With Quote
Old 11-14-2011, 05:42 PM   #3
Too Short? Cut it Again!
 
Join Date: Sep 2009
Posts: 9,635
Default

foam over batts


Most 2" foam board is not fire rated and in some instances can be a real fire hazard. You will probably be in violation of fire codes. Even if you sneak it in and something goes wrong? Your insurance company will have a great reason to deny a fire claim.

Last edited by user1007; 11-14-2011 at 05:46 PM.
user1007 is offline   Reply With Quote
Old 11-14-2011, 09:06 PM   #4
Newbie
 
Join Date: Oct 2011
Posts: 12
Default

foam over batts


Quote:
Originally Posted by sdsester View Post
Most 2" foam board is not fire rated and in some instances can be a real fire hazard. You will probably be in violation of fire codes. Even if you sneak it in and something goes wrong? Your insurance company will have a great reason to deny a fire claim.

I agree, also no more or less than spray foam is fire rated...but the drywall will be. I don't plan to leave the walls bare. It will simply be batts in a studded wall, 2" foam board on the studs over the batts, drywall over that.

Also I understand that idealy I would want the foam right on the concrete but in this case the exterior walls are already studded...can't really get the foam in there now unless I spray foam it $$$$$. And I don't want to rip the studs out either...
Ram Guy is offline   Reply With Quote
Old 11-15-2011, 09:43 AM   #5
Don't WANNA do it myself
 
mnp13's Avatar
 
Join Date: Jan 2007
Location: Rochester, NY Area
Posts: 617
Default

foam over batts


If those bats are right up against the concrete, I'd check them for mold.
mnp13 is online now   Reply With Quote
Old 11-15-2011, 05:26 PM   #6
Newbie
 
Join Date: Oct 2011
Location: Westfield, IN
Posts: 17
Default

foam over batts


Agreed. The first problem is that you don't want a vapor barrier over bats in a basement as that will trap moisture coming off the concrete. Using xps as the vb that way may make it worse if it moves the condensation point into the fiberglass.

Do you have any space behind the studs?

Have you looked into the DIY spray foam kits? Like foamitgreen.com? Moe expensive than xps, but it would seal tight to the studs and even if you only got an inch in there, you could use bats on top.

I've never used it and I haven't seen much in the ways of review here, but from what I understand of spray foam, this might work and not be too much more expensive than xps sheets with tape, caulk, etc.
TimMauriello is offline   Reply With Quote
Old 11-15-2011, 06:13 PM   #7
Newbie
 
Join Date: Oct 2011
Posts: 12
Default

foam over batts


Quote:
Originally Posted by TimMauriello View Post
Agreed. The first problem is that you don't want a vapor barrier over bats in a basement as that will trap moisture coming off the concrete. Using xps as the vb that way may make it worse if it moves the condensation point into the fiberglass.

Do you have any space behind the studs?

Have you looked into the DIY spray foam kits? Like foamitgreen.com? Moe expensive than xps, but it would seal tight to the studs and even if you only got an inch in there, you could use bats on top.

I've never used it and I haven't seen much in the ways of review here, but from what I understand of spray foam, this might work and not be too much more expensive than xps sheets with tape, caulk, etc.

VB is code here...Using foam board is a much better VB than improper poly in my opinion. I have looked into those DIY spray foam kits, and they are definatly pricey. I don't know that they are MUCH cheaper than getting the pros to spray it.But I appreciate the input.
Ram Guy is offline   Reply With Quote
Old 11-15-2011, 08:44 PM   #8
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Default

foam over batts


Rigid foam board stores moisture going through the concrete wall to release it slowly drying to the inside. An air permeable insulation as f.g. will not slow any moisture. In fact the dew point will change from the concrete/f.b. to the f.g. because you have moved it from concrete to the interior side. Your f.g. will get wet and lose 60-70% of the R-value: http://www.nrc-cnrc.gc.ca/eng/ibp/ir...ling-heat.html
The paper facing will mold: http://www.inspectapedia.com/sickhou...rglassMold.htm

The correct way: http://www.buildingscience.com/docum...ts?full_view=1

Here is the problem: http://www.buildingscience.com/docum...researchreport

The foamboard will stop about 91% of the heat loss making the cavity colder (yet warm enough to mold), it needs to be next to the concrete: 2” foamboard = R-10= 2.78” of f.g. @ 3.6: http://www.enersavesystems.com/pdf/E...Insulation.pdf

Where are you located, as already asked? Looking for a State/Providence, not physical address…

Gary
__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Old 11-15-2011, 09:49 PM   #9
Newbie
 
Join Date: Oct 2011
Posts: 12
Default

foam over batts


Thanks Gary. And I'm in Calgary Alberta.
Ram Guy is offline   Reply With Quote
Old 11-15-2011, 10:23 PM   #10
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Default

foam over batts


Ahhhh.... another member from up North. insulating basement half walls-my plan

Check locally, they may require a basement v.b. unlike here in the U.S. Though reading the sites, you do have some foamboard with strapping- no vapor or air barrier, depends on your basement Class finishing per Code.

Gary

__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Spray Foam into walls behind kitchen cabinets? MovedTooMuch Insulation 4 09-21-2011 09:33 AM
Looking for suppliers for Low E foam board and fiberglass batts viper Building & Construction 1 06-02-2011 02:02 AM
How To Install Rigid Foam Insulation on Concrete earthad1 Building & Construction 9 10-26-2010 09:49 AM
Replace Flange in basement with Foam? mattoxda Plumbing 1 10-10-2010 04:05 PM
Hybrid wall insulation consisting of 2" rigid foam + 2x4 fiberglass batts? TitaniumVT Building & Construction 15 09-14-2010 02:50 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.