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-   -   Insulating Basement (http://www.diychatroom.com/f103/insulating-basement-129892/)

danjag 01-14-2012 01:12 AM

Insulating Basement
 
I built my 2x4 walls in my basement 1 inch from the concrete wall and am about to insulate with Roxul, a batt type insulation which will sit nice and snug within my 16" centered studs. My question is whether I should push it towards the back of the wall so it touches the concrete or push it only as far so it's flush with the studs, thus leaving an air gap behind?

I solved any water penetrating problem from the outside by having a new weeping tile system installed and applying blue skin and insulating with R10(2" XPS from the footing to just below the grade. Although a problem I am having and thus hesitating on how I will place my R14(Roxul) insulation is that I have some very extreme cold spots that are generally in 1 corner on a painted surface above grade which I have lots of water condensing. I am going to spray foam these areas to help add R value along with the batt insulation but I am generally concerned with what will happen to any moisture that is going to be present between the concrete wall and my insulation in other areas if a -45 deg C week comes along in the future.

My studs have been sitting for months so they are dry by now and my basement is dry as well. I will be using a dehumidifier during the summer months and will be installing a vapour barrier before drywalling. Thanks in advance for helping.

titanoman 01-14-2012 07:39 AM

Flush it with the studs so you can staple the paper (barrier) to the inside front of the studs.

danjag 01-14-2012 10:23 AM

My insulation is supposedly mold and moisture resistant but I don't want mold growing behind my insulation against the wall. So your saying to allow the space behind the insulation and allow the air to circulate?

titanoman 01-14-2012 10:49 AM

Quote:

Originally Posted by danjag
My insulation is supposedly mold and moisture resistant but I don't want mold growing behind my insulation against the wall. So your saying to allow the space behind the insulation and allow the air to circulate?

I would think so.
I'm not sure if you need any type of a barrier over the concrete or not.

Gary in WA 01-14-2012 06:03 PM

Where are you located?

No air gaps: http://joneakes.com/jons-fixit-database/743

Gary

danjag 01-15-2012 03:31 PM

I am located in Thunder Bay, Ontario, Canada.

I will place my mold and moisture resistant Roxul against the wall. Will the cold wall condense water behind the insulation if it's flush with the wall or will the insulation not allow for air to get into those areas and thus not cause water to condense?

I only have a few bad spots where the walls get extremely cold where it condenses and I plan on spray foarming those spots in addition to putting the Roxul

Bob Mariani 01-15-2012 06:00 PM

you need at least 2" closed cell spray foam to keep the exterior wall warm enough to prevent condensation

mae-ling 01-15-2012 06:21 PM

Although spray foam is a good idea t is not absolutely necessary, 2" foam board would work as well.
Do a search for basement insulation on this forum. It has been discussed a lot.

Bob Mariani 01-15-2012 06:23 PM

if the basement walls are straight and even enough. You do not want any space behind the foam board.


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