Polyiso insulation sealant / caulk
#1
10-16-16, 03:28 PM
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
10-17-16, 03:29 AM
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
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
10-17-16, 06:12 AM
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.
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.
#4
10-17-16, 06:31 AM
Busy so don't have a lot of time to reply, but here are a couple of good links.
What Happens When You Put a Plastic Vapor Barrier in Your Wall? | GreenBuildingAdvisor.com
All About Vapor Diffusion | GreenBuildingAdvisor.com
Bud
What Happens When You Put a Plastic Vapor Barrier in Your Wall? | GreenBuildingAdvisor.com
All About Vapor Diffusion | GreenBuildingAdvisor.com
Bud
#5
10-18-16, 04:51 AM
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
https://buildingscience.com/document...in-crawlspaces
Figures 6 & 7
http://www.jm.com/content/dam/jm/glo...awl_Spaces.pdf
