Spray Foam On Brick Wall… Close or Open Cell?
Per the excellent advice and columns on GBA I have decided to go with close cell under the roofing deck and gable ends of an old house project in climate zone 5.
If I may ask one more question concerning the brick interior step wall (see link).
http://perlworks.com/misc/broad/SouthBed_closet_bare.jpg
Should I use open or close cell spray or maybe even something like cellouse?
I plan to furr out the wall with either 2×4 or 2x6s. I have read close cell on brick interior can cause problems with brick to be wetter in the winter and result in long term duribility problems.
However in my case I have a stucco exterior that keeps the exterior mostly dry. I am a bit leerying of placing an impermeable stubstance against the interior wall in the case of some unforseen problem with breathability. The house is over a century and I don’t want to screw up the durability.
Here is what the exterior looks like.
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Replies
Trucckaxle,
I'm assuming you still have questions after reading this article: https://www.greenbuildingadvisor.com/blogs/dept/musings/insulating-old-brick-buildings
Steve,
You really do have an almost encyclopedic knowledge of the contents of this site.
Steve
Yes I read that article. My situation is different in that the brick is not exposed to the exterior but has a stucco finish.
Yes, stucco is a porous reservoir finish as well that I assume was directly applied to the brick. Yours appears to be painted. Do you know how many layers of paint are there? Is it vapor permeable? Whether you see liquid water coming through the mortar joints or not it is safe to assume that the back side of that brick wall is helping dry the assembly. Where you have brick and wood intersecting I would have some concern that capillary breaks are not in place, and the system is relying on the drafty walls to convectively dry everything.
Long story short, you can either pay a consultant to do some testing on the brick & stucco assembly, or accept some higher level of risk by going forward with any of our recommendations. As the article states, there is no straightforward answer to whether it will work out or not.
If you are confident in proceeding with the insulation, Closed Cell spray foam is the consistent recommendation given. You can combine the spray foam with batt insulation to achieve your desired R Value. Your concerns about moisture and durability could be evaluated by a consultant, but vapor permeable insulations would not be the solution.
A way out of the box, more involved option that you could consider would be to preserve the interior brick face for historical value and apply a continuous external insulation system (like EIFS, etc). But I am betting you are not interested in this route.
I don't know what the right answer for you is, but the general recommendation is that closed-cell against the brick is usually okay if you've done a really good job of making sure your roof overhangs, drip edges, and flashing details are all in tip-top shape.
One non-foam option that may or may not be appropriate for your situation is listed at the very bottom of this article in Figure 9: https://buildingscience.com/documents/building-science-insights-newsletters/bsi-095-how-buildings-age
That said, it looks like in your situation getting a good seal with the smart vapor barrier in the approach described in figure 9 might be unreasonably difficult, pushing you back to closed-cell foam as most likely the way to go.