Replies

1. 
   DaveRicheson | Oct 18, 2004 02:57am | #1

   Just WAG, but do you mean foundation wall? I would think footers in Vermont would be beneath the frost  depth of maybe 4".

   Nothing wrong with rigid foam on the outside of a concrete wall. EIFS are  exterior insulating finish system that use rigid foam.

    Get the stuff with borate in it, or you will be providing a nesting area for burrowing insects. They don't feed on it but love to make thoer burrows and nest in it. Borate traeted foam keeps'm out.

   Dave

1. 
   mdresimprov | Oct 18, 2004 05:08am | #3

   Thanks for the reply. My mistake, foundation wall it is.

2. 
   VaTom | Oct 18, 2004 04:13am | #2

   Putting insulation on the outside of a concrete wall doesn't sound like a good idea to me.

   Actually, it's the best place.  Keeps the mass inside the insulation to moderate temp swings.  Something critical in my house(s).  Cloud once dug out a gov't report along those lines, but I have no idea what thread it was.

   I used steel studs to attach the siding here, then went to copper Z strips as we use copper siding.  Ground contact issues must be addressed, of course.  Is 2" of rigid insulation adequate?  That's what we use here, in a 4166 degree-day climate.  Burlington is almost twice that.

   A footer 1-5' above grade?  No idea what that is.  Maybe the foundation wall? 

   PAHS Designer/Builder- Bury it!

1. 
   mdresimprov | Oct 18, 2004 05:14am | #4

   Thanks. Foundation wall it is. It seems that insulating the outside would keep that concrete mass cold and still provide for a chilly interior. Based on your calcs.I'll look into 4 in. of foam.

   MES

1. 
   VaTom | Oct 18, 2004 02:39pm | #5

   It seems that insulating the outside would keep that concrete mass cold and still provide for a chilly interior.

   That can happen with huge mass, but won't with your small mass.  We use mass for the vast majority of our heating needs, but we're heating it up over the summer (cooling the house in the process).  In your case, the mass will heat up from your space heating and store that heat (assuming proper insulation), making the room much more comfortable. 

   Ever talk to someone living in a log structure?  They always tell me how comfortable it is, well-insulated.  Comfortable, yes, well-insulated, almost never.  It's the mass that's working there.  Your client's house will be no different, except that you will add insulation on the outside of the mass, where it should always be.

   Our first winter here the walls of our concrete house were uninsulated, only concrete between us and the snow.  Wasn't particularly uncomfortable, simply burned a little more wood.  Heat loss calculations work well to predict how any particular structure will perform.  Is 4" right for you?  I don't know, just guessed 2" to be skimpy.PAHS Designer/Builder- Bury it!

1. 
   mdresimprov | Oct 18, 2004 04:46pm | #6

   Thanks for helping me make sense of it of it all. I should know better, just had one of those brain freezes. Thanks again!

   MES

2. 
   JohnT8 | Oct 18, 2004 05:54pm | #7

   VaTom is right, the outside is the best place for it from an energy efficiency point of view.  You wind up adding the concrete wall to the 'thermal flywheel' of the house.  You're looking at about 5-8R per inch, depending which foamboard you use.  XPS (extruded polystyrene --pink or blueboard) is suitable for above or below grade applications (about 7R/inch).  EPS (expanded polystyrene, --white board) is suitable for above grade (about 5R/inch).

   And Dave mentioned the down side of exterior foam: bugs.  Gotta keep the bugs out.  They don't feed on foam, but they do find it a easy material to work with and are hard to get out once in.  Best bet is to keep them out in the first place.jt8

1. 
   mdresimprov | Oct 18, 2004 06:51pm | #8

   Thanks John....good info.

   MES