Replies

1. 
   cameraman | Jan 21, 2011 04:46pm | #1

   Finish it like a basement

   I am not a professional carp, but I have renovated more homes than most.

   I would finish like a basement, cover the walls with a dow foam board, tape joints,  and stud a wall in front of it.

   Break the thermal bridge of cold against the block walls and place the best insulation that I had the $$ for, spray foam between the studs if you can afford it. Fiberglass at last resort.

   just my 2 cents

1. 
   arthur1111 | Jan 22, 2011 02:01pm | #3

   Vapour barrier or not?

   Thank You, I will go that route.

   The new plan is to  cover the blocks with a 1"dow foam board,  tape the joints, stud a 2x3 wall in front of it, insulate with fiberglass insulation (since its above ground,).... and here is were I am not sure, should I apply vapour barrier? 

1. 
   DanH | Jan 22, 2011 03:47pm | #4

   What's your typical minimum winter temp, down there in Toronto?  I'm guessing about -20C is the lowest low you see for more than a day or two most years?  Then you probably don't need a vapor barrier.

2. 
   DanH | Jan 21, 2011 06:55pm | #2

   The main purpose for housewrap is as a wind barrier.  It also serves as a secondary rain barrier.  You don't need either of these with block construction, assuming it's reasonably sound.

   I agree with the other poster that you probably should handle it sort of like a basement.

1. 
   davidmeiland | Jan 23, 2011 01:11pm | #6

   Air barrier

   Read the first part of this http://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-water-resistive-barriers

3. 
   warrenblack1 | Jan 23, 2011 11:24am | #5

   vapor barriers are location dependent

   Each part of the world has a differing requirement for vapor barriers and the harm or good served by the presence of or lack there of is dependent upon the inside vs outside temperatures, the humidity inside vs outside and this is  also the material involved . Think of wood/straw/ bamboo vs concrete or brick.

   The clearest discussion I have understood on this subject is from a group of scientists and engineers which have a website: buildingscience.com

   I'm not either, just a builder,but my take is that you probably can ignore a vapor barrier for the plan you have given. But look up these folks. I think I have avoided a lot of errors due to the unformation they supply.

4. 
   davidmeiland | Jan 23, 2011 01:13pm | #7

   How is

   the electrical wiring installed?

1. 
   arthur1111 | Jan 24, 2011 01:35am | #13

   No Vapor Barrier
   Yes, having 2" rigid foam and strapping on top would save a lot of space... my concerns with doing it in this way, one the blocks are not plumb and strait (especially bad for the kitchen)... two, wiring would be a challenge.

   Thanks to all of your posts I have decided not to apply the vapor barrier on the stud walls, I figure that the rigid foam in-between the block and the interior stud wall will act as one, here is how I understand it, correct me if I am wrong.

   Moisture in the summer will want to flow from exterior to the interior, it will permeate the block but should stop at the rigid foam (hopefully without condensing).

   In the winter moisture will want to flow from interior to the exterior it will again permeate the stud wall and fiberglass insulation but should stop at the rigid foam (again hopefully without condensing.)

   The idea is that the 1" foam (R4) is enough to stop condensation and if at the extreme end of the temperature range should condensation accrue, it will not be trapped between the vapor barrier and the rigid foam.

   Do I understand this correctly?

1. 
   Geoffrey | Jan 23, 2011 05:57pm | #8

   Arthur,

   In the winter moisture will want to flow from interior to the exterior it will again permeate the stud wall and fiberglass insulation but should stop at the rigid foam (again hopefully without condensing. The idea is that the 1" foam (R4) is enough to stop condensation and if at the extreme end of the temperature range should condensation accrue, it will not be trapped between the vapor barrier and the rigid foam.

   I'm not an expert in building science, but I have concerns, where then will the moisture condense?The foam board will be the coolest surface and that's exactly where it will condense, in the wall. The VB should be placed on the stud face with the drywall right over it This will keep the moisture from entering the wall cavity at all, as is the desired effect for your climate zone. The foam board will keep the moisture from entering the stud wall cavity during the summer months(from the exterior). Moisture in the block should be addressed by exterior finishes.

   Your circumstance is typical of a North East  climate, only farther North, so your degree heating/cooling days requires your VB

   on the interior, not the exterior of the wall. The foam board will prevent penetration from the outside into the interior wall cavity and moisture "within" the exterior wall (CMU) should be addressed by the exterior finishes.

    Just my 2 cents worth,

   Good Luck

             Geoff

1. 
   arthur1111 | Jan 23, 2011 07:38pm | #10

   My thinking... if there is no condensation on my double pane window glass (R3) at -20*, would it be safe to say that there would not be any condensation on an R5 1" rigid foam board?

1. 
   DanH | Jan 23, 2011 07:45pm | #11

   Likely, but a little short of "safe".

2. 
   arthur1111 | Jan 24, 2011 01:31am | #12

   I just don't want to do more
   I just don't want to do more harm than good by applying VB on the interior... it seems to me that VB on one side of the stud wall and foam board on the other would encapsulate the fiberglass insulation and would make it impossible to dry out should moisture find its way in.

   Maybe I should stick to the original plan, that is apply felt paper on the block, frame a wall in front, insulate with fiberglass insulation, apply vapor barrier and drywall. In this way the fiberglass insulation would have a better chance of drying out (in the winter) should it get wet.

   Does anyone have any better ideas?

3. 
   DanH | Jan 24, 2011 07:21am | #14

   I think you'd be safer with 2" of foam, with or without a VB.

   The problem with any of these hybrid insulation approaches is that it's difficult to guess at the temp/humidity profile through the wall, to know if the humidity is apt to reach 100% at any point -- you need either some rigorous calculations or a well-tested practice.  That web page I pointed to does some calculations, but unfortunately hides the humidity profile and just tells you if there's a condensation "risk".

4. 
   arthur1111 | Jan 24, 2011 10:08pm | #15

   DanH thank you for all your help... I will go with the 2" foam board.

2. 
   DanH | Jan 23, 2011 06:26pm | #9

   You might want to try using this site -- better suited for you than us anyway:  http://www.vesma.com/tutorial/uvalue01/uvalue01.htm