Good Building Score: 17

Recommendation: Avoid

Zip-R takes a problematic system and dramatically ramps up the failure risk. Adding vapor closed, low density, foam insulation is going to underperform in terms of energy savings and carbon impact. More importantly, the moisture failure risk of the system increases with the addition of foam insulation.

The foam insulation is adhered to the interior side of the OSB. This means it’s nearly impossible to sufficiently tape (or otherwise seal) all of the seams in the foam layer. If there isn’t best practice interior side air and vapor control (which is pretty rare) then warm humid interior air can sneak through the foam seams and find the OSB. If it happens to be colder outside than inside the risk of condensation is now pretty darn high.

Since the Zip system is typically vapor closed at the seams, the condensation can build up over time and cause issues.

Please also see our analysis of Zip System.