Insulating Basement

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Old 04-04-13, 07:42 PM
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Insulating Basement

I am in the process of finishing my basement. After researching all the different ways to insulate exterior walls I have come to the conclusion that closed cell rigid foam board glued to the wall is the way to go (is this correct?). However, I have a dilemma. My main cast iron sewer drain is running down the wall on 2 of the 4 exterior walls, with only about a half inch of space between the drain and the concrete wall. What would be the best way to insulate these walls?
 
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Old 04-06-13, 03:33 PM
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I'd use 1/2" where you have to, add thicker when possible. IMHO, don't insulate in front of it to let room heat keep it warm. Where in PA?

Gary
 
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Old 04-06-13, 09:36 PM
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South central pa. Doesn't get that cold in the basement.
 
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Old 04-06-13, 10:01 PM
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Just as a tip, there's no need to insulate any part of any wall that is below grade.
 
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Old 04-07-13, 11:11 AM
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Using Huntingdon, PA as a base for temps, your average low of Jan, Feb, Dec. is 23*F. That would also be the temp of your basement wall 3' below-grade and above. Below that, the temp would warm the deeper you go. 6' down is about 10*F warmer than surface temps.

Not to insulate for your location would be foolish, if one understood it better. Compare this: http://www.quadlock.com/technical_li...Insulation.pdf

The frost depth is 36", and your State code requires you follow the 2009 IECC; pp.4, #9, and pp.5, #12e;https://docs.google.com/viewer?a=v&q...V5mCPqOqOBS55A

You are in Zone 5 (not below that white dotted line = areas you don't insulate basements);Chapter 3 - General Requirements

Zone 5 requires R-10/13 or 2" foamboard inside OR R-13 insulation inside, see footnote "c"; Chapter 4 - Residential Energy Efficiency
Notice footnote "f"-- no basement insulation= Zone 3 and less only.

Using your 3 months average again, this time of the highs and lows, is 31*F outside. So, down to the frost depth plus above grade, your basement wall would be about 30*F during winter. Because there is some heat gain in the basement now, either from rooms above or furnace/ducting below, the basement may not seem cold. Right now, you may not see any condensation on the concrete walls due to basement air currents wicking it away as it forms. Once you cover the walls with frame/insulation/drywall, the walls/drywall may get wet; 31*F soil/concrete wall + 68*F room air = 39*F or 35% Relative Humidity. With a 2x4 frame wall + R-13 + R-10 (2"XPS), at 68*F room air; inside f.b. temp is 48*F or safe from condensation at/below 49%RH basement air.

IF your local AHJ will let you; R-5fb +R-13= 42*For 38%RH ----- R-7.5fb +R-13= 45*F or 44%RH as you still have the R-13 to meet code.

Gary
 
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Old 04-07-13, 03:12 PM
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Old 04-09-13, 03:17 PM
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Will you have the required headroom for the living space? Or egress from the rooms? I'd route the copper water supply line on the inside of the foamboard. Set the frame wall on 1"" XPS for a thermal/air/capillary break for the cold earth/slab; Pressure-Treated Sill Plates and the Building Code | GreenBuildingAdvisor.com

Gary
 
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