vapour barrier question

nohandleMarch 19, 2010

My basement currently has a four foot cement block foundation wall topped with a 3+ foot wood stud wall to the ceiling. I am building a 2x4 wall in front of the existing walls flush to the ceiling, which will give me room to insulate the block wall and add electrical receptacles as well. This means there will be a lot of insulation in the top half (existing stud wall), but that's ok with me (I don't want to create a ledge either).

To create a thermal break between the foundation and the stud wall, I was going to attach some xps to the foundation wall, and add batt insulation over top in between the new studs. It is my understanding that a foundation wall covered in this way does not require a vapour barrier on the warm side, since the xps is a vapour barrier in itself. However, the top half of the wall (existing stud wall) is above grade and therefore requires a vapour barrier on the warm side of the insulation.

My question is, am I going to create problems if I add a poly vapour barrier over the batt insulation on the entire wall, considering that I will have xps attached to the foundation on the bottom half of the wall?

I am trying to do this as economical as possible, which is why I'm not insulating entirely with xps or spray foam.

A compromise may be to add a layer of xps against the sheathing on the top part as well and skip the poly altogether.

Any insight/suggestions would be appreciated.

Thanks.

Thank you for reporting this comment. Undo
worthy

According to Building Science Corp., it does no harm to add an (unnecessary) vapour barrier atop the XPS in the basement. That's exactly what building inspectors have required me to do on new builds.

    Bookmark   March 19, 2010 at 5:15PM
Sign Up to comment
More Discussions
water in unfinished basement
Well its in the 50s here in NJ and the snow is melting....
hoganjr
New Home Build - window size for drywall?
Apologies if this has been asked before - can't seem...
lookintomyeyes83
Adding toilet to basement
We are adding a half bath to our basement when we start...
Seamer1
making the crawl space more useful?
My house has a (vented) crawl space between 2 and 3'...
gigelus2k13
Str'l Wood Floor + CrwlSpace vs Concrete Slab
Hello, We were discussing our plans with a builder...
lookintomyeyes83
Sponsored Products
Progress Lighting Wall Mounted Satin Aluminum 2-light Wall Lantern P5512-16
Home Depot
Tom Dixon | Fat Spot Floor Lamp
$565.00 | YLighting
eLIGHT LED Vapor Tight Light Fixture
Overstock.com
Accent Rug: Lokoja Marine Blue 2' x 3' Flatweave
$46.97 | Home Depot
Zephyr 30W in. Siena Wall Mounted Range Hood - ZSI-E30AS
$799.00 | Hayneedle
Chpg 206116R or 206166-R 23.8 ft C6 Green Wire 70 LED Christmas Lights
EnvironmentalLights.com
PW 78313R 16.6 ft C7 Green Wire 25 LED Christmas Lights
EnvironmentalLights.com
White Arm & Hammer Odor-Neutralizing Grommet Curtain Panel
$12.99 | zulily
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™