Should I use drywall or OSB as the air barrier?
jeffnmaine
| Posted in General Questions on
Zone 5 in Maine. Stackup is: vertical siding, Hydrogap, OSB, 2×6 with Roxul.
Question is: Should I use drywall or OSB as air barrier in between 2×6 wall and the 2 inch utility chase which will also be insulated?
If drywall, should it be paperless/ fiberglass?
Looking for experiences including Joe L’s method.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Jeff,
A few brands of OSB aren't quite airtight, so builders who obsess about airtightness usually don't use OSB as an air barrier. For more on this issue, see Is OSB Airtight?
Some builders install OSB between a stud wall and an interior service cavity, as you propose, and detail it as an air barrier. They do this because (a) They are willing to roll the dice when it comes to the airtightness of the brand of OSB they purchase, (b) They like the fact that this type of air barrier is durable and protected from abuse by occupants, and (c) They like the fact that OSB is a "smart" vapor retarder with variable permeance.
There are lots of ways to build a wall. For more information, see How to Design a Wall.