Replies

1. 
   Shoeman | Jan 22, 2005 06:57am | #1

   when I finish basements here in Minnesota, I put 2" ridged foam against the block, tape all the seams and the foam also works as vapor barrier, then stud wall with no insulation and drywall right on studs no other vapor barriers.

   Not sure where you are and how much insulation you need  -  the 2" foam is only R-10 if I remember correctly - that's enough to satisfy code for a MN basement

2. 
   sarison | Jan 22, 2005 07:00am | #2

   I think you need to contact Mike Smith about his insul. details.  

3. 
   woodguy99 | Jan 22, 2005 10:09pm | #3

   The new issue of FHB has an article on finishing a basement.  It might help you.

4. 
   DanH | Jan 23, 2005 12:58am | #4

   There is a special sort of rigid foam that is made for insulating masonary. The edges are notched so you can glue up the foam, then insert 1x3 or some such in the adjacent notches, and "shoot" that to the wall to secure it. Then regular drywall or whatever can be attached to the wood.

   No wood in contact with the masonary, no breaks in the insulation, but you still have a good mounting surface for finish materials.

5. 
   Frankie | Jan 23, 2005 01:30am | #5

   FWIW:

   2" Rigid foam is rated at 7-10 R value. $16 - $20/ 4x8.

   3 1/2" Fiberglass is rated at 13-15 R value. $.36 - $.54/ sqft.

   Do the math.

   If the walls are damp - ever - use rigid.

   F.

1. 
   Piffin | Jan 23, 2005 03:09am | #6

   More to the math than just that. It costs more to stud a wall that furr over foam from the lumber aspect. And you can save roughly an inch.BTW, you can have foam that is rated R7 for just one inch. Two gives you R14 and less convective heat loss. 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

2. 
   Taylor | Jan 24, 2005 02:25pm | #7

   Depends on what your foam is. XPS (Styrofoam) is R-5. Polyisocyanurate is rated R-7.x, but cures to R-6.x. The polyiso boards I see are foil-faced which would not be appropriate in a basement

1. 
   MikeSmith | Jan 24, 2005 04:11pm | #8

   andy engel just did a great picture article on eps foam  and insulating a basement

   you could do a lot worse than use that as your modelMike Smith Rhode Island : Design / Build / Repair / Restore

2. 
   RichBeckman | Jan 24, 2005 04:39pm | #9

   "The polyiso boards I see are foil-faced which would not be appropriate in a basement"I read this to mean that it is the foil-face which is inappropriate for a basement.But why is that??Rich BeckmanAnother day, another tool.

1. 
   Taylor | Jan 24, 2005 05:03pm | #10

   Ok someone correct me if I'm wrong, but I am under the impression that foil facing is a VB. Hence buildingscience.com's admonition to use (unfaced) XPS.

1. 
   RichBeckman | Jan 25, 2005 03:38am | #11

   "Ok someone correct me if I'm wrong, but I am under the impression that foil facing is a VB. Hence buildingscience.com's admonition to use (unfaced) XPS."Thanks.Rich BeckmanAnother day, another tool.

2. 
   CubsWin | Jan 25, 2005 04:03am | #12

   I building a media room in my basement and was planning on placing 2" EPS (not foil faced) on the concrete block walls and frame the walls with 2x4's.  However, I would like to fill the 2x4 wall cavities with fiberglass insulation to help with resonance and accoustics within the room.  Do you see anyting wrong with both EPS and fiberglass insulation.

   Thanks,

   Brian

3. 
   Piffin | Jan 25, 2005 04:56am | #14

   That's fine, but use unfaced FG batts. Also, they make a denser FG batt that is supposed to be helpfull accoustically 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

4. 
   Piffin | Jan 25, 2005 04:05am | #13

   Ya, the foil face is a VB, but so is XPS.The only reason I can think of for hesitation in using the polyiso foil faced in a cellar is that is is open celled so it can harbor water. It would all depend on whether moisture is likely to be a problem.I just got tyhe latest FHB today and breezed thru the article showing Andy doing his stuff. Didn't read the text,yet but the pics all look like good stuff to emulate. 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

5. 
   Taylor | Jan 25, 2005 01:51pm | #15

   "...the foil face is a VB, but so is XPS."Not true. Dow will say very carefully that XPS is a vapor retarder, not a VB (so don't sue them if your XPS permeates). Buildingscience advocates XPS without a vapor barrier for basement insulation because any moisture that leaks behind the insulation permeates back....slowly. EPS permeates better but has lower R-value.

6. 
   Piffin | Jan 26, 2005 04:55am | #16

   Fine enough to be technically correct - but for practical purposes, it functions as a VB, between the low perm and the insulation denying dew points. BTW, there is nothing that does not have some degree of permeability, even waterproof roofing membranes. it is just a matter of using adequate perms where needed. 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!