Polyiso insulation sealant / caulk


  #1  
Old 10-16-16, 03:28 PM
T
Member
Thread Starter
Join Date: Jan 2015
Location: USA
Posts: 885
Received 72 Votes on 66 Posts
Polyiso insulation sealant / caulk

We're preparing to insulate with foil faced polyiso sheathing to create a vapor barrier. In addition to tape, we want to apply a caulk / sealant at the seams. We can't find the product we want - Tremco Spectrem 1. It would be helpful if someone can recommend an alternative.
 
  #2  
Old 10-17-16, 03:29 AM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,531
Received 42 Votes on 38 Posts
Hi Tony,
My question would be, why the vapor barrier?
VB's have been discouraged in recent years as they can, in some applications, cause more harm than good. Where they are desired a foil faced rigid insulation board would provide a significant reduction in vapor movement without any tape or caulking. The primary purpose of the tape is to air seal to prevent that mode of moisture movement.

As for the foil facing, there is only one brand (to my knowledge) that has been accepted to meet codes as a thermal barrier, Dow Thermax and even this product may need local approval.

Bud
 
  #3  
Old 10-17-16, 06:12 AM
T
Member
Thread Starter
Join Date: Jan 2015
Location: USA
Posts: 885
Received 72 Votes on 66 Posts
Bud, thanks for your comments. My inquiry is the latest in a series on two problems we're trying to solve on a bump out bathroom: water pipe insulation and cold bathroom temps. (I've included pictures.) Our plan is to use unfaced insulation between the joists in the picture and create a vapor barrier using foil faced insulation under that. The disposal pipes will be protected by building a box around them and doing the same.

We want to create as good a vapor barrier as we can. Thus, the desire for taping plus caulk / sealant.

BTW, yes we'll be putting plastic over the concrete floor.

Finally, we'll be adding OSB as a final step as a thermal barrier to comply with code requirements for rigid insulation over storage areas.
 
Attached Images   
  #4  
Old 10-17-16, 06:31 AM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,531
Received 42 Votes on 38 Posts
  #5  
Old 10-18-16, 04:51 AM
T
Member
Thread Starter
Join Date: Jan 2015
Location: USA
Posts: 885
Received 72 Votes on 66 Posts
Bud, I don't want to take up any more of your time. Clearly the approach I described isn't traditional. You may be interested in the articles I used as the basis for my question, in effect building a micro encapsulated crawlspace:

https://buildingscience.com/document...in-crawlspaces
Figures 6 & 7

http://www.jm.com/content/dam/jm/glo...awl_Spaces.pdf
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: