Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Building & Construction

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

Reply
 
Thread Tools Search this Thread Display Modes
Old 08-11-2011, 09:06 PM   #1
Newbie
 
Join Date: May 2011
Posts: 12
Share |
Default

Insulating basement of split level home.


I'm in Ottawa Canada and I will be insulating my split level home's basement and wanted some advice on how to properly insulate the foundation walls.

My basement ceiling is 8 feet high. The foundation walls are 4 feet in the ground and the framing on top of the foundation is a regular 2x4 wall that ISN'T flush with the concrete wall....it juts to the outside anywhere from 1/2" to an inch. The basement is dry.

All of the research I've done points to only building a knee wall up to the top of the foundation and leaving the rest as is but I'm thinking of putting 2" XPS foam just high enough to cover the concrete foundation (4 feet) and building a 2x4 wall in front of that from concrete floor to bottom of joists but I'm not sure how I would tie a vapour barrier in for the top half of the wall. Is there a right way to do this? Or better yet, what is the preferred method of insulating a basement in a split level?

Here are some pics:




mmastran is offline   Reply With Quote
Old 08-11-2011, 09:33 PM   #2
Member
 
AGWhitehouse's Avatar
 
Join Date: Jul 2011
Posts: 1,378
Default

Insulating basement of split level home.


You could run 2" foam from floor to ceiling and cover with sheetrock for the code required thermal and ignition covering required over foam. Will need to slice up the existing vapor barrier on the batt insulation to eliminate any moisture traps. The foam, providing proper thickness and composition, will provide the vapor barrier required of your geographical region.

Looks like any method you go with on the concrete will involve relocating the HVAC louver seen in the bottom right corner of your second photograph.

__________________
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
Old 08-11-2011, 09:39 PM   #3
Newbie
 
Join Date: May 2011
Posts: 12
Default

Insulating basement of split level home.


Quote:
Originally Posted by AGWhitehouse View Post
You could run 2" foam from floor to ceiling and cover with sheetrock for the code required thermal and ignition covering required over foam. Will need to slice up the existing vapor barrier on the batt insulation to eliminate any moisture traps. The foam, providing proper thickness and composition, will provide the vapor barrier required of your geographical region.

Looks like any method you go with on the concrete will involve relocating the HVAC louver seen in the bottom right corner of your second photograph.
Thanks for the reply. I was thinking of running the foam up the entire height of the wall but there would be anywhere from 1/2" to 1" of space between the the back of the XPS foam and the existing rockwool insulation on the top 4' wall since it doesn't sit flush with the concrete foundation.
mmastran is offline   Reply With Quote
Old 08-11-2011, 09:51 PM   #4
Member
 
AGWhitehouse's Avatar
 
Join Date: Jul 2011
Posts: 1,378
Default

Insulating basement of split level home.


Quote:
Originally Posted by mmastran View Post
Thanks for the reply. I was thinking of running the foam up the entire height of the wall but there would be anywhere from 1/2" to 1" of space between the the back of the XPS foam and the existing rockwool insulation on the top 4' wall since it doesn't sit flush with the concrete foundation.
Run 1/2" or 1" foam on the lower part and then overlay with full height with thickness needed. Since not every stud is exactly a 1/2" or 1" off the foundation, you can shim the studs out with gypsum board furring strips to get the stud faces flush to accomodate the full height foam.
__________________
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
Old 08-13-2011, 11:05 AM   #5
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Default

Insulating basement of split level home.


With only 4500+ HDD for your location, foam up past the concrete wall would be an over-kill for the money, in my opinion. It would also be putting the majority of the insulation in the stud bay rather than outside it to keep the wall sheathing warmer for less condensation problems. This would also slow the drying to the inside from an exterior water leak at the wood frame wall above grade. Your area requires R-13 cavity insulation, more than enough with two layers of batt (R-24) rather than foam board too (R-29).


Any gap between insulation or on the foam board/concrete would be prone to convective loops. Use the saved money on foam board and canned foam at the rim joists to air seal; pull the ineffective faced batts from there. Pull the paper facing from the batts, just slashing it would do next to nothing. Slashing would compromise an air barrier but not a vapor barrier or retarder.



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 08-15-2011, 11:06 PM   #6
Newbie
 
Join Date: May 2011
Posts: 12
Default

Insulating basement of split level home.


Gary, thanks for the reply.

Should I use a polyethylene VB on the top 4' or the whole of the basement wall, or at all?

Quote:
Originally Posted by GBR in WA View Post
With only 4500+ HDD for your location
Sorry, what does this mean?


Quote:
Originally Posted by GBR in WA View Post
It would also be putting the majority of the insulation in the stud bay rather than outside it to keep the wall sheathing warmer for less condensation problems.
What you suggest sounds different than what I had in mind on how to insulate. I've included an image from someone on the Mike Holmes forum with a similar basement setup as my own. The MAIN DIFFERENCE in mine is that the interior wall I'll build will sit IN FRONT of the XPS foam that insulates the lower 4' concrete foundation. The wall will run from the concrete slab to the bottom of the floor joists.

Any suggestions/improvements/changes you see?

thanks again!
Attached Thumbnails
Insulating basement of split level home.-basementinsulationsketch_version3_w.jpg  

Last edited by mmastran; 08-15-2011 at 11:30 PM.
mmastran is offline   Reply With Quote
Old 08-16-2011, 12:17 AM   #7
Framer
 
Join Date: Jun 2011
Location: Canada
Posts: 44
Default

Insulating basement of split level home.


Why not build a frost wall away from the concrete wall? Space it 1 inch from the concrete foundation and run it from your slab to the bottom side of your floor joists. Insulate all the way up with batt insulation and vapor barrier all with a good bead of acoustical sealant on the bottom to stop airflow.

Thats how we do it here...

Best of luck
joeyr is offline   Reply With Quote
Old 08-17-2011, 11:53 AM   #8
Member
 
AGWhitehouse's Avatar
 
Join Date: Jul 2011
Posts: 1,378
Default

Insulating basement of split level home.


Quote:
Originally Posted by GBR in WA View Post
Slashing would compromise an air barrier but not a vapor barrier or retarder.
Sorry, but this makes no sense.
__________________
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
Old 08-17-2011, 12:06 PM   #9
Member
 
AGWhitehouse's Avatar
 
Join Date: Jul 2011
Posts: 1,378
Default

Insulating basement of split level home.


Don't build that wall. The 2" of xps at the exterior coupled with a poly layer at the interior will create a double retarder system and will greatly increate the likelyhood of mold growth.

The foam from bottom to top would act as both an isulation barrier and vapor retarder. (2" of XPS is .75 perms which is a class II retarder).
__________________
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
Old 08-17-2011, 12:09 PM   #10
Member
 
AGWhitehouse's Avatar
 
Join Date: Jul 2011
Posts: 1,378
Default

Insulating basement of split level home.


Quote:
Originally Posted by GBR in WA View Post
This would also slow the drying to the inside from an exterior water leak at the wood frame wall above grade.
I would think that if the siding system fails he has more problems than where a vapor retarder is. vapor retarders are suppose to be on the warm-side-in-winter. That means at the interior considering the OP is in Canada. Can you explain why you are against the code standard?
__________________
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
Old 08-17-2011, 12:28 PM   #11
Newbie
 
Join Date: May 2011
Posts: 12
Default

Insulating basement of split level home.


Quote:
Originally Posted by AGWhitehouse View Post
I would think that if the siding system fails he has more problems than where a vapor retarder is. vapor retarders are suppose to be on the warm-side-in-winter. That means at the interior considering the OP is in Canada. Can you explain why you are against the code standard?
Guys, I appreciate all of the feedback...I really do
but I'm nowhere closer to figuring out how to properly insulate my basement given my PARTICULAR scenario.
Here's a recap: I'm in Ottawa, Canada and my basement is 8 feet (4 foot below grade, 4 foot above grade). I want to build a 2x4 wall from slab to floor joists...no knee walls. If I were to use 2" XPS on the top 4' above grade, and 1 - 1.5" XPS on the 4' below grade, do I need a VB? See pics above for what my basement looks like.

thanks,
mmastran is offline   Reply With Quote
Old 08-17-2011, 03:33 PM   #12
Member
 
AGWhitehouse's Avatar
 
Join Date: Jul 2011
Posts: 1,378
Default

Insulating basement of split level home.


Quote:
Originally Posted by mmastran View Post
If I were to use 2" XPS on the top 4' above grade, and 1 - 1.5" XPS on the 4' below grade, do I need a VB?
The foam itself at 2" is a class II vapor retarder. At 1" it is a class III. So if you ensure there is at least 2" of foam, then you will have a 0.75 perm, class II vapor retarder. I don't know your local code, so I'm not sure if you need a class I or class II.

Class I Vapor Retarder = 0.1 perms or less
Class II Vapor Retarder = 1.0 perms or less and greater than 0.1 perms
Class III Vapor Retarder = 10 perms or less and greater than 1.0 perms

DOW 1" thick XPS is 1.5 perms...
__________________
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
Old 08-17-2011, 09:38 PM   #13
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Default

Insulating basement of split level home.


You may have some local modifications to your Code; http://www.about-building-in-canada.com/provincial.html

I haven't study this yet, only skimmed it, pp. 61--- onward addresses the vapor barriers: ftp://ftp.cmhc-schl.gc.ca/chic-ccdh/..._Web_sept5.pdf

To simply slash a vapor barrier will have effect only where the small slash is, letting through more air as a v.b. is area calculated. An air barrier is based on no holes or slashes; http://www.greenbuildingadvisor.com/...cience-podcast

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 08-18-2011, 11:33 AM   #14
Member
 
AGWhitehouse's Avatar
 
Join Date: Jul 2011
Posts: 1,378
Default

Insulating basement of split level home.


Quote:
Originally Posted by GBR in WA View Post
To simply slash a vapor barrier will have effect only where the small slash is, letting through more air as a v.b. is area calculated. An air barrier is based on no holes or slashes; http://www.greenbuildingadvisor.com/...cience-podcast
The first paragraph of the link supports my confusion. I think you're assuming a single cut of the vapor retarder. I'm talking about slicing and dicing, or two continuous, overlapping, serpentine cuts that allow for the removal of "diamonds" along it.
__________________
Life's too short...so enjoy it!
AGWhitehouse is offline   Reply With Quote
Old 08-20-2011, 11:45 AM   #15
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Default

Insulating basement of split level home.


Now you described it correctly--- remove the facing. Any facing, slashed or not is a retarder.

Should the joints be taped?
Johns Manville does not recommend nor require that the joints be taped. Vapor retarders
are area weighted. The small gaps would not allow a significant amount of water vapor
through the wall, ceiling or floor.” From: http://www.insulating-products.com/p...lation_FAQ.pdf


To simply say “slash it” implies leaving it in place, at least to me, glad you added further instructions.

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 insulating joists in basement? peethree Building & Construction 13 11-28-2010 08:54 AM
At a crossroads in my basement project - waterproofing help needed callisto9 Building & Construction 35 10-28-2010 02:01 AM
Level basement sewer outflow question nmc Plumbing 6 05-22-2010 01:29 PM
Insulating to stop air infiltration in the basement. diy4life Building & Construction 51 06-11-2009 08:30 AM
Insulating - Rim/Header Joist - Basement AndrewF Building & Construction 7 02-26-2009 11:10 PM




Top of Page | View New Posts

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