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Finishing basement guidance

1042 Views 6 Replies 4 Participants Last post by  Gary in WA
Hello all first time here joined bc i need some expert guidance. Planning basement refinishing. Area is eastern pa. Going with steel framing. Have the rimjoist sealed with 2 in xps with bat ontop of. Now for the question. Walls are poured concrete no cracks or deterioration no signs of water in the 2 yrs I lived there. I have a waste line running 3/4 around basement walls so I will have to frame in front if it approx 4 in off wall. What do I need for insulation. I am not planning of forced air in basement just electric fire place as heating source when needed. I am torn about the 2 in xps on walls. Is it necessary. I hate to incur that cost as it would be 1200 on xps alone. Can I just put fiber batt between framing since I'm off the wall 4 in minimum. I'm not terribly concerned about the insulation aspect as far as warmth goes as it is tolerable down there in all seasons. For what it's worth most of basement is below grade with exception of one wall. I'd hate to spend the extra 1200 for xps but will if it is the correct thing to do. I read every which way and every opinion but cannot decide if it is necessary since I currently have no water and am off wall by 4 in minimum. Thanks for your input
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Welcome to the site.
Having a location with questions like this is always a big help.
There has to be a couple thousand post on this one subject on this or any DIY site.
Main thing you may see is people removing the rotten drywall and finding the insulation covered with mold and or soaking wet.
In most cases that 2" of foam is pretty important.
Just to update this. I am leaning towards 1.5 in xps. My concern is I still would have approx 3 in standoff from the xps due to the waste line. Building science states frame tight to xps I don't have this option. Additionally how do i manage creating an airtight seal around horizontal waste line. Should I put xps above and below pipe and just spray foam behing pipe as best I can?
How about a picture?

How much insulation are you going to need? 1.5" is good, but more is better here.

Have you tried to look for foam recyclers or other foam reclamation?

The issue with fibrous insulation is the ability of moisture to pass through and condense on the now colder surface of the foam (colder as a result of the fiber insulation).
"since I currently have no water and am off wall by 4 in minimum."------------ no moisture on the walls because you have warmed the wall/floor so interior basement air currents dissipate any moisture immediately. That will change once you insulate; the cold concrete wall will condense moisture and on the framing wood, also possibly the fibrous insulation to degrade it's R-value by up to 60%- if I remember correctly.

Continuous foam board may require R-100, OR R-15, depending on where you are in Eastern PA;

Foam is the safest way BUT builders paper/fibrous insulation is also possible, read Post #16 and #19- follow my links;

Many houses have the main drain line run diagonally across the back concrete wall- from top to bottom. If you use code thickness FB, any gap to the frame wall is non consequential. Actually better not to have cavity insulation as then the room/cavity will be same temp controlled entirely by the HVAC system. IMO, add a vapor barrier on the rim joist foam to prevent any condensation in winter/summer, Don't add fibrous insulation there if fb is to code (same as wood frame walls) because you will be making the fb run colder being in direct contact with the rim/siding and lowering its dew-point for easier condensation.

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Thanks Gary. Just so I'm clear just cut fb just below and above and do not fill the.5 inch gap being the drain line with spray foam? Also on rim joist I cut to fix 2 in xps and spray foam cracks on all side. I do have bat currently tucked on top in the rim joist cavity. Thanks for the links I'll check them out. I live in SE pa near del boarder. I'm hoping to get away with 1.5 on wall and either roxul of fiber r15 in framing. Would you think it best since I will have approx 3 in standoff from frame to fb to fill that cavity with 5 in deep roxul or fiber insulation to reduce airflow between framing and fb everything I have read from builfing science calls to frame up to fb and fill stud Bay with insulation. What are your thoughts. Thanks again.
Sent a PM for 1-on-1.

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