Masonry Interior Retrofit: Foam-less advice
We’ve got a project where we are proposing to insulate an existing 19th century brick building in northern NY state to the interior with cellulose with the goal of a minimal spray foam retrofit.
Reasons for avoiding foam include permitting renovation in the future by not glueing the building together, toxicity & GHG blowing agents in US spray foam. Some foam will still likely be used for air sealing at tricky areas, but want to avoid it as much as possible.
Building is a triple wythe brick building with no visible signs of water intrusion on the interior face of brick, staining or the like, exterior has been repointed for this job. It’s in really good shape overall. If we insulate to the interior, the brick will now stay cold all winter, but this building has not been occupied full time for the past decade, so it’s survived cold walls already.
Interior face of brick has vertical wood furring strips attached to the brick that used to support the plaster and lathe.
Proposed plan is as follows:
Staple Typar or Asphalt Felt to the vertical furring strips, tie into window openings with construction tape.
Build 2×4 stud wall off face of brick for a total cavity of 10″ (R-3.8 x 10″ = R-35+)
1/2″ CDX Plywood interior sheathing as airbarrier, taped and sealed to existing floor boards and ceiling, pieced into joist bays for continuity as best possible.
Drywall on Plywood.
Theory is to create interior air barrier, allow drying to outside. Typar or Asphalt felt will prevent any moisture intrusion from wetting the cellulose, but still allow drying outward.
Options instead of the Typar to serve as a WRB / air barrier on brick include StoGuard EmeraldCoat (http://www.stocorp.com/index.php/component/option,com_catalog2/Itemid,196/catID,38/catLevel,3/lang,en/subCatID,128/subCatIDnext,131/) or Thoroseal (http://www.thoroproducts.com/products_waterproofing.htm) parged onto interior face of brick for WRB and air sealing.
Any thoughts about this plan from everyone? Any experience with these techniques out there?