# Unfinished Basement Space



## Windows on Wash (Aug 30, 2011)

If there's insulation in the wall of the garage, you will require that much less between the spaces because the rate he lost to the garage we lessened. Do not mistake lessened insulation for lessened need of air sealing. Make sure there's no communication between the spaces.

You should not require an additional vapor barrier and demonstrating the performance and performance specifications of the foam should dissuade the inspector from insisting on an additional vapor barrier.


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## Gary in WA (Mar 11, 2009)

Welcome to the forum!

If you go the fiberglass/poly sheeting route, you may have condensation below grade if not perfectly air-sealed; http://www.buildingscience.com/docu...ing-hygrothermal-modeling-basement-insulation

Your location codes require a vapor barrier of 60 perms; equal to our Vapor retarder of asphalt-coated kraft paper;* pp.70- 925.4.2;* http://www.buildingscience.com/docu...ing-hygrothermal-modeling-basement-insulation You can also use XPS at a little more than one inch thick to meet this; XPS; 1.1 or 1.5 perm per inch, depends on brand--------- *pp.48, *same link.

Poly* below-grade* is inferior to unfaced XPS; pp.27/68 to 30/68 and pp47/68= safe with *poly above-grade*;ftp://ftp.cmhc-schl.gc.ca/chic-ccdh...ngual/Vapour_Permeance_Volume_1_Web_sept5.pdf

http://www.nbec.net/documents/POTEN...ASTICSHEETINGINWALLASSEMBLIES-DAVIDDEROSE.pdf

Check with local AHJ using those links.

Gary
PS, 1 more; http://www.buildingscience.com/documents/information-sheets/building-materials-property-table/

If you do use a faced FB, make sure there is 2-3' above-grade concrete exposed or you will drive the wet concrete wall moisture to the sill plate/rim joist as it cannot diffuse into room.


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## zzeuss (Dec 30, 2011)

wow.. thank you very much for all those information..
Now I have lots of readings to do.. 
thanks again!!


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## zzeuss (Dec 30, 2011)

Gary in WA said:


> If you do use a faced FB, make sure there is 2-3' above-grade concrete exposed or you will drive the wet concrete wall moisture to the sill plate/rim joist as it cannot diffuse into room.


I think I going to go with XPS (1.5") instead. In that case, I'll use the board from top to bottom and seal all the gaps.. or do I still need 2-3' above grade exposed??


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## Gary in WA (Mar 11, 2009)

Ontario is very big in area; https://www.google.com/search?q=map+of+ontario%2C+canada&ie=utf-8&oe=utf-8

As I don't have your specific location,,, Using the 3 coldest monthly averages from here, though your location may differ; https://www.google.com/search?q=map+of+ontario,+canada&ie=utf-8&oe=utf-8

https://www.google.com/search?q=map+of+ontario,+canada&ie=utf-8&oe=utf-8

With 68*F in basement, inside surface of foamboard (1-1/2") and R-14 Roxul, will be 47*F on the above-grade and down to your frost depth; http://www.urecon.com/applications/images/canadian_map_lrg.jpg

At 47*F, you would be safe against condensation up to 48% Relative Humidity in room. 

No, the exposed portion is only when using foil-faced or impermeable facers. Install the FB with 1' square (roughly) grid pattern of adhesive (foam compatible) to limit air movement there; http://joneakes.com/jons-fixit-database/743 Canned foam the perimeters, esp. on the slab, FB the wood rim with FACED FB, after caulking/sealing the wood joints against air from infiltration- cutting the board at perimeter for canned foam/caulking application. Thin FB, or at least fan-fold or sill sealer under the wood bottom plate w. a bead of caulking under/above that to stop air. ADA the drywall; http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach/

Gary


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## zzeuss (Dec 30, 2011)

thanks again for so much of good information!!

We live in northern part of Toronto.. (South part of Ontario).
Winter gets quite cold.. especially past 2 winters.. lol..

I just sent an email to city explaining my situation.
Below is the steps I described to city and asked them to confirm an extra layer of Vapor Barrier is not needed.. since I don't want any surprises when an inspector came to inspect our house..


--------------------------------------------------------
We are thinking of using below rigid foam(XPS).
FOAMULAR C-300 Extruded Polystyrene Rigid Insulation - 24 Inch x 96 Inch x 1.5 Inch Ship Lap Edge
(http://www.homedepot.ca/product/foa...igid-insulation-24-inch-x-96-inch-x-15/925587)
step 1. Put these 1.5"rigid foams right against the walls (R7.5) acts as vapour barrier
step 2. Stud the wall with 2x4
step 3. Fill the gap with Roxul brand batts (R14)
step 4. Drywall and Paint and but Vapour Barriers on warm side


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## Gary in WA (Mar 11, 2009)

"step 4. Drywall and Paint and but Vapour Barriers on warm side"------ not an interior vapor barrier of poly.... of asphalt faced tar paper. Not needed- the FB gives you the 1 perm required by code.

WATER VAPOUR PERMEANCE, max.


Perm 0.87

(ng/Pa.s.m 
2
)
50
From; http://insulation.owenscorning.ca/assets/0/188/58cb329e-6ca2-4e54-a8cf-b4e7cf4586ea.pdf

Gary


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## zzeuss (Dec 30, 2011)

Oh.. thanks for catching that up..
I meant to say NO vapor barrir on the warm side..
I have to let my city know ... lol..
Thanks again....


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## BarryP (Jun 14, 2015)

Make sure you have the manufacturer's specs with you. Building officials are not to follow the good advice of buildingScience. They need manufacturer info


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