Hi all! We live simply outside Halifax, NS, Canada, climate Zone 6. We are putting up a new building, and I have a concern about vapour retarders.
Our wall buildout (interior– > outside) on the ground level is: drywall, 2 × 6 framed cavities with Rockwool R24 ComfortBatt insulation, sheathing, VaproShield barrier (orange frogskin), Rockwool ComfortBoard 80 R6 outside insulation, strapping/air cavity, wood siding.
The wall buildout upstairs (loft areas, all open to the interior of the building) are the exact same, other than the gable ends, knee walls, and rim joists are carried out in closed cell foam instead of R24 Rockwool ComfortBatt.
We have two heat pumps going into the structure, mostly for Winter heat however also for some restricted air conditioning in the Summer season. The piece is insulated.
I have actually checked out multiple short articles (some on GBA) and used a calculator that takes a look at interior vs. exterior insulation, overall wall buildout, and environment zone to generate a recommendation for what (if any) vapour retarder to utilize in our circumstance … I am seeing suggestions for Class I behind the drywall, Class II behind the drywall, and none whatsoever.
Our home, surrounding to the new structure and finished in 2015/16, has the exact same wall buildout as explained above however with open cell spray foam in the main floor wall cavities (rather of Rockwool ComfortBatt) and utilizes a Class I vapour retarder under the drywall. However, we do not have a heat pump/do not air condition the interior space at any point of the year. We have relatively dry Summers and Falls here with a lot of air motion throughout, and simply opening and closing windows manages our interior environment just fine in your house. The new structure is a workshop area in which environment control is more of an issue (storing a lot of large sheets of paper, for instance), however we still expect the cooling/air conditioning requires to be light/low/infrequent.
I am practically done packing the wall cavities with Rockwool and have to determine how to proceed with/without/what-type of vapour retarder. I am tempted to do what we carried out in the house, due to the fact that although we will be doing some a/c, it will be pretty low-intensity … however I would enjoy to hear plastic sheeting may cause more damage than great, and either transfer to a Class II or go without totally.
Any insights?