Will closed-cell insulation prevent bricks (and the mortar) from drying out and eventually falling off of the wall?
Ryan Byrd
| Posted in General Questions on
My condo association says that closed cell insulation sprayed directly to the back of a brick wall will not allow the brick to dry because there is now airspace, and thus the brick will eventually fall. Is this true?
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Replies
Ryan,
There are two kinds of brick wall. The most common kind is a brick-veneer wall. A building with brick veneer walls usually has wood-framed structural walls; the brick facing is thin (only one wythe thick), and is basically a type of siding.
Older brick buildings have multi-wythe brick walls that are structural. This type of wall might be have three or four wythes of brick. This type of wall actually supports the roof.
If you live in a brick veneer building, the condo association is absolutely right. The air space behind brick veneer is an essential part of the system. The gap is necessary for drainage and drying. The gap behind the bricks in a brick veneer wall should never be insulated.
If you live in an older building with multi-wythe brick veneer walls that are structural, your condo association may still be right. Such walls can be risky to insulate. More information here: Insulating Old Brick Buildings.
Never say never- there are instances where cavity walls can be safely insulated- it's commonly done in the UK where brick veneer is one of the most common construction types. But in general it's more likely to create problems down the line. The specific issues of concern are both construction & climate dependent.
Where it's done in the UK the preferred method is to use blown adhesive-coated EPS beads, which form a highly vapor permeable and not very air tight insulating layer. In the US it's more often done (at some risk) with multi-polymer non-expanding injection foam (eg Corefill 500, TriPolymer, etc.), which is fairly vapor permeable compared to comparable-R polyurethane foams, though with more than an order of magnitude less drying capacity than the EPS bead solution, and several orders of magnitude lower drainage capacity. SFAIK the blown EPS solution is not available anywhere in North America (though it might be a useful retrofit in US climate zones 4 & lower, if it were.) See:
http://www.nbba.org.uk/why-blown-bead.htm
http://www.hometherm.ie/cavitywall-new_build.html
Dana,
I don't think cavity walls in the U.K. are built the same way as brick veneer walls in the U.S.
While brick veneer walls in the U.S. almost always have wood-framed structural walls (often sheathed with OSB), cavity walls in Britain often have structural walls of concrete block or tile block. These walls are much more robust (and much less likely to fail) if they get damp than an OSB-sheathed wood wall.