# Insulating basement of split level home.



## AGWhitehouse (Jul 1, 2011)

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.


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## mmastran (May 19, 2011)

AGWhitehouse said:


> 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.


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## AGWhitehouse (Jul 1, 2011)

mmastran said:


> 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.


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## Gary in WA (Mar 11, 2009)

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


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## mmastran (May 19, 2011)

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?



GBR in WA said:


> With only 4500+ HDD for your location


Sorry, what does this mean?




GBR in WA said:


> 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!


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## joeyr (Jun 25, 2011)

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


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## AGWhitehouse (Jul 1, 2011)

GBR in WA said:


> Slashing would compromise an air barrier but not a vapor barrier or retarder.


Sorry, but this makes no sense.


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## AGWhitehouse (Jul 1, 2011)

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).


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## AGWhitehouse (Jul 1, 2011)

GBR in WA said:


> 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?


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## mmastran (May 19, 2011)

AGWhitehouse said:


> 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 :thumbup:
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,


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## AGWhitehouse (Jul 1, 2011)

mmastran said:


> 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...


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## Gary in WA (Mar 11, 2009)

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...ngual/Vapour_Permeance_Volume_1_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...ier-or-vapor-barrier-building-science-podcast

Gary


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## AGWhitehouse (Jul 1, 2011)

GBR in WA said:


> 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...ier-or-vapor-barrier-building-science-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.


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## Gary in WA (Mar 11, 2009)

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/pdfs/Installation_FAQ.pdf


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

Gary


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## mmastran (May 19, 2011)

*Insulating basement of split level home - Final thoughts*

Gentlemen,

I appreciate all your input and I've read all the links to the documents suggested (buildingscience, cmhc, etc...). Man my brain hurts 

From the reading, I've concluded that I'll be implementing the following scenario (crude not to scale attached image)

Just a recap: Reside in Ottawa, Canada. Home is 46yrs old and basement is bone dry.

Are there any final thoughts/recommendations before I go ahead and build it?

thanks again!


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## AGWhitehouse (Jul 1, 2011)

I don't feel that the foam board shown within the stud wall is really worth your time and $ for the insulative gain. The labor and $ involved with cutting the foam to fit and scraping the left overs doesn't gain you much in terms of overall R-value. The continuous insulation bypasses the thermal bridgin of the studs. Here's another thread that has a breakdown of a similar wall type that shows the minimal difference. (note the titles are backwards though...)

http://www.diychatroom.com/f103/i-have-poor-mans-spray-foam-question-114413/

Plus, the foam will act as a vapor "barrier" on the exterior surface of you insulative envelope, and I don't feel that is in compliance with your regional code.


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## mmastran (May 19, 2011)

AGWhitehouse said:


> Plus, the foam will act as a vapor "barrier" on the exterior surface of you insulative envelope, and I don't feel that is in compliance with your regional code.


Thanks for the reply...
Since I've been struggling with this for awhile now and I feel that maybe I've not explained my situation as clearly as it should be.....given my basement wall setup (as shown in the diagram in my previous post) how do I go about insulating this basement given the following:
1) I want a full height wall on the interior as shown in the attached image in my previous post...with or without XPS...at this point I just want to build a wall and insulate so that it doesn't promote mold etc.....:thumbup:


I know Gary and you have given me tips/clues etc, but I still don't fully understand what you both mean.


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## mmastran (May 19, 2011)

What about the following scenario shown in the attached image?

Keep in mind, the interior 2x4 wall is tight to the foundation wall (I've read this is OK in buildingscience somewhere). I would put a vapour barrier from top to bottom on the interior wall


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## mmastran (May 19, 2011)

Found this link from the Jon Eakes site:

http://joneakes.com/jons-fixit-data...insulate-a-basement-wall-that-has-a-pony-wall

Any thoughts?


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## AGWhitehouse (Jul 1, 2011)

Here's my suggestion...


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## mmastran (May 19, 2011)

AGWhitehouse said:


> Here's my suggestion...


Much appreciated!!

I've previously thought about doing exactly what you've suggested....I'm wondering now if its overkill. Not that I don't appreciate yours and everyone's help.

When I demo'd the basement (see pictures at beginning of this long drawn out thread :whistling2 I had:
- paper faced mineral wool in the top 4' pony wall (R12?) stapled to studs. 
- concrete foundation had a thin sheet of poly stapled at the rim joist (4' mark) draped down the wall and mechanically attached with a piece of strapping around the room. The drywall on the lower half was screwed into this strapping

There were zero moisture problems within the pony wall, zero moisture on the wood strapping, zero problems with existing lumber up against the concrete foundation, zero mold on the drywall.....no mustiness, no rot, nothing....So maybe I'm just over-thinking this whole thing? I'm kinda paralyzed on how to proceed at this point what with all the information, articles, websites, forums I've read regarding this issue.

So basically I've narrowed it down to your suggestion or this:

http://www.joneakes.com/jons-fixit-...insulate-a-basement-wall-that-has-a-pony-wall

I would make the following changes to Jon Eakes' suggestion:
- remove the paper on the mineral wool batts in the pony wall.
- build a full height (8') bluwood (http://www.bluwoodcanada.com/) 2x4 stud wall in front of the foundation filled full height with R-14 batts top to bottom tight to the concrete. Fill any gaps between pony wall and new wall with ROXUL.
- use a vapour retarder (not polyethylene) sealed top to bottom on the new wall.
- cover with moisture/mould resistant drywall (popular here in Canada)


The extra money for these products combined will still be much less than using the XPS foam.


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## SteelToes (Oct 5, 2010)

One more to think about 
Whitehouse hope you don't mind revisions 

In my opinion with this option you are saving on living space and total cost of materials.


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## AGWhitehouse (Jul 1, 2011)

If you go that route, I recommend Z-channels ( http://i01.i.aliimg.com/photo/v0/226530085/acoustical_ceiling_Z_channel.jpg )in lieu of studs. Studs will create a total break in the insulation value and be a heat sink, where the channels will only be a slim heat sink. They also will hold the insulation panels in place as you move down the wall. In this scenario, be sure to tape off all studs for vapor and air intrustion and coordinate your electrical penetrations to do the same.


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