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Walk-out basement insulation


Tony P.'s Avatar
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CT

01-02-16, 09:21 AM   #1  
Walk-out basement insulation

I've come across several comments on this but can't apply them to my situation, so excuse me for asking a question that's been discussed.

I live in Connecticut. My property slopes down (front to back) and my basement is approx 55% poured concrete and 45% framed with a walk-out at grade level. See attached photo. Name:  FullSizeRender.jpg
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As you can see, there is no insulation. My question, though, relates to only the framed portion. Can I insulate the framed portion with rolled or batt fiberglass insulation? I've seen comments on moisture but don't believe that's an issue for me, given the large portion of framed walls. However, is there a humidity limit I should watch out for? Are there other considerations I should consider?

BTW, my interest in fiberglass insulation is for ease and cost.

Thanks,
Tony P.


Last edited by Tony P.; 01-02-16 at 11:02 AM. Reason: Spelling error in title
 
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Tolyn Ironhand's Avatar
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01-02-16, 09:39 AM   #2  
I see no reason you can not use fiberglass batts. If they are 2x4's you will only get an R11 or 13. If they are 2x6's that will get you an R19.

If you step up to some rigid XPS foam gives you an R5 per inch, but as you mention, at a greater front end cost.


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Bud9051's Avatar
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01-02-16, 10:06 AM   #3  
I see a partition wall, is that the framing you want to insulate or are you insulating the concrete/framed exterior walls?

Fiberglass insulation directly against a concrete wall is a potential problem in that air currents can slowly deliver humid air to a very cold surface, then you have condensation and ice. And ultimately, a mold potential. The modern day advice of adding enough rigid insulation against the concrete before the fiberglass is intended to keep the first inside surface above the dew point.

There are also minimum insulation levels required by codes and assuming your area is currently up to the 09 codes here is a link: https://energycode.pnl.gov/EnergyCodeReqs/ Using their guidelines (minimum levels) a layer of 1" of rigid, then your walls with r-13 cavity insulation would work.

I realize the 1" of rigid is more than you were thinking, but the rigid insulation keeps the inside surface warm and acts as a vapor retarder. It is a nice one step fix to many problems. Below is a link on finishing a basement, but don't forget to air seal the house to foundation area.
Understanding Basements | Building Science Corporation

Bud

 
Tony P.'s Avatar
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01-02-16, 11:07 AM   #4  
Bud, it's only the framed portion I want to insulate. Those are exterior walls with only house wrap and vinyl siding providing "insulation".

 
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01-02-16, 11:17 AM   #5  
Although the framed portion is attractive to add insulation, the sheathing and siding have about the same r-value as 8" of concrete (about r=1), so when time and dollars allow, cover that foundation.

"However, is there a humidity limit I should watch out for?" Always. The irony is, as you make improvements to reduce the heating costs, like #1 air sealing, you reduce the natural air exchange and the humidity goes up. Watch yours using an inexpensive meter and add a dehumidifier if needed. That moisture would be coming through the concrete and not the studded wall. 45% is a good maximum.

Bud

 
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