Insulating Floor Of Addition - Insulation - DIY Chatroom Home Improvement Forum

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


Thread Tools Display Modes
Old 07-03-2012, 05:59 PM   #1
Join Date: Aug 2005
Location: Portland, OR
Posts: 52
Rewards Points: 59

Insulating Floor of Addition

I am putting a small 2nd story addition on the back of our house. It is supported on columns, so the floor is open to the outside.

I am going to be using fiberglass batts between the floor joists, and am considering using a layer of 2" rigid insulation (XPS) below the floor joists (there is a bathroom with plumbing in the floor). My question is what do I do about a vapor barrier? Is it okay to use unfaced batts and use the 2" of XPS foam as the vapor barrier since it is vapor impermeable?



handyman923 is offline   Reply With Quote
Old 07-03-2012, 06:12 PM   #2
Join Date: Nov 2011
Location: Hartfield VA
Posts: 34,435
Rewards Points: 14,000

If the bottom is exposed, I'd used faced batts and Exterier rated t & G plywood, or for a better look 1 X 6 T & G on the underside.


joecaption is offline   Reply With Quote
Old 07-04-2012, 02:13 AM   #3
Join Date: Dec 2008
Location: Fairbanks, AK
Posts: 1,893
Rewards Points: 1,092

Vapor barriers are, in general, a no-go any more. Vapor retarding and air sealing is what you want to do. Your rigid foam will probably stop your joists from condensing, so I would sure use it and seal all gaps w/ Great Stuff and tape. Look for Roxul instead of fg batts; fg batts are a pp excuse for insulation.
jklingel is offline   Reply With Quote
Old 07-05-2012, 12:46 AM   #4
Registered User
Join Date: Mar 2009
Posts: 11,730
Rewards Points: 526

No vinyl flooring;

Cover for critters and fire.

If any ads are present below my answer or words underlined/colored, I do not condone/support/use the product or services listed/linked to, they are there without my consent.
17,000 dryer fires a year, when did you last clean the inside of the dryer near motor or the exhaust ducting?
Gary in WA is offline   Reply With Quote

Thread Tools
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
Insulating a kitchen sink in an addition mariann carcich Kitchen & Bath Remodeling 1 04-06-2012 07:35 PM
Incremental benefit of insulating rafters in addition to ceiling joist bays? benjamincall Insulation 13 12-26-2011 01:17 PM
Insulating Attic - Peaked Roof addition over Built-Up Roof nominivans4me Insulation 1 04-16-2011 11:27 AM
Insulating an addition cbollin Remodeling 1 02-02-2011 11:59 PM
Insulating and Underpinning a new addition annoyed Building & Construction 2 08-23-2009 05:04 PM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1