Insulation & Vapor Barrier For Joist Cavities - Insulation - DIY Chatroom Home Improvement Forum
Advertisement


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 03-28-2018, 04:18 PM   #1
Member
 
Join Date: Jan 2013
Location: great white north: Ottawa, Ontario, Canada
Posts: 31
Rewards Points: 64
Default

insulation & vapor barrier for joist cavities


I live in Ottawa, Ontario, Canada (cold climate), and our house was built in 1983. In the basement, the joist cavities at the top of the foundation wall were originally insulated with pink fiberglass insulation, and the vapor barrier was thin plastic sheeting (much thinner than the usual 6-mil vapor barrier...it seems to be around 2-mil). It was tucked around the insulation, separately in each cavity (see attached pic).

I had to remove the insulation in some of the joist cavities, to calk the cracks which were letting in a lot of cold air in winter. Done. Now I need to re-install the insulation and vapor barrier.

Is there any thin (around 2-mil) vapor barrier which is approved to use exposed in the basement like that? All the 2-mil polyethylene/visqueen sheets I've found on amazon.com don't mention any fire retardant qualities.
Attached Thumbnails
insulation & vapor barrier for joist cavities-p1260086crop.jpg  
mid-rise9 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 03-28-2018, 05:08 PM   #2
Member
 
user_12345a's Avatar
 
Join Date: Nov 2014
Location: Canada
Posts: 12,445
Rewards Points: 48
Default

Re: insulation & vapor barrier for joist cavities


i would skip the fiberglass and vapour barrier and put roxul board cut and placed in.

can put enough layers to get the r-value up high enough and foam in place.

vapour barriers suck in that area, impossible to do a good job.

you can also use foam faced with foil which u may be able to leave exposed.

with rigid u don't need vapour barrier.
__________________
I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.
user_12345a is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 03-28-2018, 05:49 PM   #3
Member
 
jlhaslip's Avatar
 
Join Date: Dec 2009
Location: Edmonton, Alberta
Posts: 5,975
Rewards Points: 708
Default

Re: insulation & vapor barrier for joist cavities


Quote:
Originally Posted by user_12345a View Post
i would skip the fiberglass and vapour barrier and put roxul board cut and placed in.

can put enough layers to get the r-value up high enough and foam in place.

vapour barriers suck in that area, impossible to do a good job.

you can also use foam faced with foil which u may be able to leave exposed.

with rigid u don't need vapour barrier.
Styrofoam / Foam to the outside would require a drywall layer on the inside.
Use closed cell foam and the plastic vapour barrier is not required, in fact it is wrong to use the plastic with closed cell because then you are trapping moisture between two sealed layers. Long story.
__________________
Quote:
Short of cutting off a body part, the worst that can happen in woodworking is manufacturing really nice looking kindling. --- Quoted from lenaitch
jlhaslip is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 03-28-2018, 06:39 PM   #4
Member
 
user_12345a's Avatar
 
Join Date: Nov 2014
Location: Canada
Posts: 12,445
Rewards Points: 48
Default

Re: insulation & vapor barrier for joist cavities


That's all correct.

someone where mentioned that foil faced foam may not need drywall over it.

Roxul board isn't flammable so it doesn't need drywall over top of it. It also has good drying potential on both sides and doesn't allow air movement through it, so no condensation risk, no reduced r-value.

It's a truly great material - only issue is one layer won't get the r-value high enough.

Main point was, there are better options than batts and vapour barrier. the barrier if it's stapled always eventually fails and isn't air tight to begin with.
__________________
I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.
user_12345a is offline   Reply With Quote
Sponsored Links
Advertisement
 
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
Basement Insulation Ontario CodeMatters Insulation 6 03-21-2018 09:14 PM
Attic insulation removal and baffle install tasligh50 Insulation 7 09-29-2017 02:53 PM
Insulating your attic Bob Mariani How To Guides 5 07-07-2013 08:49 PM
?'s about foil-faced "bubble wrap" insulation badger73 Insulation 5 06-25-2012 05:09 AM
Rafter Vents and Insulation nofx1981 Roofing/Siding 15 03-10-2010 08:14 PM




Top of Page | View New Posts