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Old 07-31-2010, 12:19 PM   #1
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XPS or Polyisocyanurate for basement


I'm about a few weeks away from starting my insulation project in the basement... was just about to order the rigid foam and noticed that polyisocyanurate foam is strangely cheaper... I was always under the impression it was more expensive..... anyways which of these would you buy? Keep in mind I am going to put a 2x4 wall infront of this and add R-13 to that in addition to this foam board....

Dow STYROFOAM 3/4" x 4' x 8' R4 Insulated Sheathing $17.72 per sheet

http://www.lowes.com/pd_14545-46086-..._?rpp=15$No=15

or


Dow 3/4" x 8' x 4' R-5 Polyisocyanurate Rigid $12.98 per sheet
http://www.lowes.com/pd_42821-236-26..._?rpp=15$No=15


Last edited by BlueBSH; 07-31-2010 at 12:38 PM.
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Old 07-31-2010, 03:36 PM   #2
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XPS or Polyisocyanurate for basement


http://www.buildingscience.com/docum...gs?full_view=1

Be safe, Gary

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Old 07-31-2010, 03:50 PM   #3
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XPS or Polyisocyanurate for basement


Not really sure that answers my question on which one to use... I already know how to insulate for my situation, just not sure if it matters which one I use or not
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Old 07-31-2010, 04:01 PM   #4
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XPS or Polyisocyanurate for basement


Quote:
Originally Posted by BlueBSH View Post
Not really sure that answers my question on which one to use... I already know how to insulate for my situation, just not sure if it matters which one I use or not
For a basement use the XPS.
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Old 07-31-2010, 04:12 PM   #5
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XPS or Polyisocyanurate for basement


Sorry. The article brings out to use non-faced foam board. Poli is faced, three layers of : http://docs.google.com/viewer?a=v&q=...dtkIjjvMMJW5yA

You want the water vapor to pass through the board and dry on the room side. Only latex paint, no v.b., no air space, sill sealer under p.t. plate for thermal/capillary break.
More recent studies suggest minimum 2" foam board for thermal protection against condensing.


Be safe, Gary
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Old 08-01-2010, 01:29 PM   #6
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XPS or Polyisocyanurate for basement


XPS tongue & groove


Owens corning 1" XPS 150 T&G is around $10.00 +/- $1 around here.

2" is $20.00 +/- ( Menards )
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Old 08-01-2010, 04:01 PM   #7
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XPS or Polyisocyanurate for basement


ok I guess one last question... since I am framing a 2x4 wall infront of this and filling it with R-13 fiber glass insulation, should the be faced or not? some stuff I read says yes, some says no the XPS is the vapor barrier (which isn't it semi permiable? doesnt some vapor still get through?)
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Old 08-01-2010, 06:20 PM   #8
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XPS or Polyisocyanurate for basement


http://www.buildingscience.com/docum...lation-systems

Particularly page 9 /10 / & 14 but read it all if you like.

Probably won't find unfaced R-13 , just take the paper off .

Last edited by High Gear; 08-01-2010 at 06:28 PM.
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Old 08-01-2010, 08:22 PM   #9
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XPS or Polyisocyanurate for basement


Quote:
Originally Posted by High Gear View Post
http://www.buildingscience.com/docum...lation-systems

Particularly page 9 /10 / & 14 but read it all if you like.

Probably won't find unfaced R-13 , just take the paper off .
amazingly my local lowes has R-13 batts unfaced available
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Old 08-01-2010, 11:08 PM   #10
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XPS or Polyisocyanurate for basement


Good deal its always nice the less glass dust you stir up.

I have 1" foam with r-13 glass , I will be calling the

plasterer this week.
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Old 08-02-2010, 06:40 AM   #11
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XPS or Polyisocyanurate for basement


when the foam board says "sheething" does that imply it has a facing? I know that means it can be used like plywood sheething is on the outside of the house when it is SIS but you wouldnt use that in a basement would you?
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Old 08-04-2010, 10:08 PM   #12
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XPS or Polyisocyanurate for basement


BlueBSH, I am doing about the same thing as what you are describing. I am using Owens Corning 2" XPS. My local Home Depot has them. About $15 for 2ft x 8ft.
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Old 08-04-2010, 11:12 PM   #13
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XPS or Polyisocyanurate for basement


Looking good! Remember required egress from a basement: http://illowaicc.org/uploadedFiles/I...20Openings.pdf

Foam board the rim joist: http://www.rd.com/57548/article57548.html

Sill sealer under the p.t. plate, a capillary and thermal break: http://www.greenbuildingadvisor.com/...-building-code

Be safe, Gary
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Old 08-05-2010, 07:56 AM   #14
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XPS or Polyisocyanurate for basement


Quote:
Originally Posted by GBR in WA View Post
Looking good! Remember required egress from a basement: http://illowaicc.org/uploadedFiles/I...20Openings.pdf

Foam board the rim joist: http://www.rd.com/57548/article57548.html

Sill sealer under the p.t. plate, a capillary and thermal break: http://www.greenbuildingadvisor.com/...-building-code

Be safe, Gary

I just finished 90% of my rim joist job... hit some snags with it though, some joist cavities had hvac riser ducts going into them for the 2nd floor and they where right against the wood it seemed like... so made it almost impossible to do.... for those ones I just spray foamed around the joints to seal it up then fiberglassed it with R-30 that was about 7 joist bays out of the ~110 joists I had to fill.. currentlu struggling with one 30 ft wall that is one long cavity (its running parallel with the joists) on one end the space is about 3 inches open (due to the basement wall beign framed in 2x4's and drywalled already I lost about 5 inches of space to get into it) so I had to find a way to get it up into there which wasnt hard but foaming around the gaps has been an interesting challange... made myself a longer flexable tube wand to stick up in worked great so far... but the problem is the other end... the gap is only about 1" so I can get the foam in but then I cant see a thing and the gas line comes in there and there is a water faucet... so im stumped on that end on what to do.... once I get that done im done with rim joists..... yay!


now my problem...... XPS in my area doesnt seem to come in toung and groove at lowes..... just "square edge" and lowes is really the only easy to get to lumber store around here anymore...... use to have an 84 lumber but that went away... any problems with using square edge and bonding the pieces together with glue then taping them or what would you do in this case?
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Old 08-05-2010, 08:00 AM   #15
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XPS or Polyisocyanurate for basement


what is the tape called you use on the joints? we always called it tyvek type (yea i know thats a brand... but we always just called it that)... is it just normal housewrap tape? I'm having a heck of a time finding it at lowes....... i can find houe wrap just no tape....

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