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Old 10-19-2010, 08:42 PM   #1
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XPS thickness for NJ basement


Im planning on finishing a basement in NJ. From searching this forum, reading online and building science materials, XPS is the way to go.

What is the difference between Owes Corning Formular 150 and 250? Is 1" thickness the correct thickness if I plan on using unfaced insulation? Im going to build conventional 2*4 framed walls.

Lastly talking with the local building inspector they arent too familar with XPS? How would I introduce them to this and get away without using a vapor barrier (plastic)?

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Old 10-19-2010, 09:38 PM   #2
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XPS thickness for NJ basement


Tell the inspector to get a dictionary or use Google.

XPS is Extruded Poly Styrene (usually tinted) as opposed to EPS, which is Expanded Poly Styrene (usually white bead board) that is best used for cheap coffee cups and meat trays at Walmart.

He must be an ex-carpenter or out of work school teacher.

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Old 10-19-2010, 10:18 PM   #3
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XPS thickness for NJ basement


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Originally Posted by casnj View Post
Im planning on finishing a basement in NJ. From searching this forum, reading online and building science materials, XPS is the way to go.

What is the difference between Owes Corning Formular 150 and 250? Is 1" thickness the correct thickness if I plan on using unfaced insulation? Im going to build conventional 2*4 framed walls.


150 is their 15 psi foam, while 250 is their 25 psi foam. Means very little in a vertical postion like you're intendign to use it in, as th e250 is merely intended to be used under weight bearing substrates, typically concrete floors. Save the money and opt or the 150.

Lastly talking with the local building inspector they arent too familar with XPS? How would I introduce them to this and get away without using a vapor barrier (plastic)?

As for the VB, are you sure your ode requires it below grade. It's a newer code here, but VB's are not allowed below grade here. Worst case scenario, get the insulation inspection and puncture the VB everywhere before drywall.............


Quote:
Originally Posted by concretemasonry View Post
Tell the inspector to get a dictionary or use Google.

XPS is Extruded Poly Styrene (usually tinted) as opposed to EPS, which is Expanded Poly Styrene (usually white bead board) that is best used for cheap coffee cups and meat trays at Walmart.

He must be an ex-carpenter or out of work school teacher.

Don't sugar-coat it Dick............
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Old 10-19-2010, 10:59 PM   #4
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XPS thickness for NJ basement


2", anything less won't keep the inside warm enough not to condense. "
The best insulations to use are foam based and should allow the foundation wall assembly to dry inwards. The foam insulation layer should generally be vapor semi impermeable (greater than 0.1 perm), vapor semi permeable (greater than 1.0 perm) or vapor permeable (greater than 10 perm) (Lstiburek, 2004). The greater the permeance the greater the inward drying and therefore the lower the risk of excessive moisture accumulation.
Up to two inches of unfaced extruded polystyrene (R-10), four inches of unfaced expanded polystyrene (R-15), three inches of closed cell medium density spray polyurethane foam (R-18) and ten inches of open cell low density spray foam (R-35) meet these permeability requirements." http://www.buildingscience.com/docum...ent-insulation
Remember a sill sealer under the p.t. plate for a thermal and capillary break: http://www.greenbuildingadvisor.com/...-building-code
No air space for convective loops at foam/batts. Fire-stopping every 10" lineally and across top plate.
Gary



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Old 10-20-2010, 07:57 AM   #5
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XPS thickness for NJ basement


Thank you all for replying.

GBR in WA - the 2" of XPS I have read conflicting information. One website says do 2" and one says do 1". The reasoning Im reading for the difference in thickness is to do with water vapor or air movement. I also dont believe I have seen 2" formular 150 in the orange store. Thoughts?
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Old 10-20-2010, 12:24 PM   #6
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XPS thickness for NJ basement


I have seen that conflict because of their earlier writings, the latest is 2". Go for the 1" in a mixed climate, 2 for cold climate: http://www.finehomebuilding.com/desi...retrofits.aspx.

A different study with Polyiso, ESP, and no framing gap, larger thickness: http://www.swinter.com/services/docu...Insulation.pdf
This hasnt been read by me yet as Im still working on it--- may be a copy: http://www.swinter.com/news/document...sulSystems.pdf

The finer details of the foam board and some more tests: http://docs.google.com/viewer?a=v&q=...w-to_GUhNOquwg


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Old 10-20-2010, 12:40 PM   #7
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XPS thickness for NJ basement


thanks that clears up the 2" and 1". Last concern I have from reading is off gassing from xps. Is this really a concern as this might remain uncovered for a year
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Old 10-20-2010, 04:50 PM   #8
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XPS thickness for NJ basement


There is something in everything.... most of it not good. http://www.healthyhouseinstitute.com...ation_Overview

I would suggest foil faced if left exposed that long. http://www2.iccsafe.org/cs/committee...E_06_64_07.pdf

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Old 10-20-2010, 04:55 PM   #9
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XPS thickness for NJ basement


I believe all foams are petro based, and so off-gas. That is a great product for your situation, though, so ventilate well and call it a day. Something like a 20 cfm fan running 24-7 should help a lot. You should ventilate 7.5 cfm/occupant, plus 1 cfm/100 sqr ft of space, according to ASHRAE specs (double check my numbers on that).
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Old 10-21-2010, 05:50 AM   #10
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XPS thickness for NJ basement


warren OR monmouth county ? ? ? big difference in temps,,, yes, a thru-the-wall air exchanger,,, but, unless you've got a toll brother's home, do a moisture test FIRST,,, there are some historic problems w/bsmt wtrproofing in nj because of the bldg code - also suggest the radon test.
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Old 12-06-2010, 11:16 AM   #11
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XPS thickness for NJ basement


with conventional 2x4 framing Im going to have about 3" from the foundation to the back of the stud. For NJ do I use a 1"/2" xps? Lastly I should purchase insulation that touches the xps or leaves a gap

Thanks

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