ZIP R-System over Masonry Walls
Hello and happy weekend!
Has anyone out there on Green Building Advisor designed or installed a ZIP R-System over an existing masonry wall?
We are embarking on a masonry overclad retrofit project on our home in Chicago and evaluating the options. An interior insulation retrofit at this point in time is out of the question.
There is overclad precedent from Building Science Corporation (https://www.buildingscience.com/documents/insights/bsi079-deep-dish-retrofits) and at that time, they elected for a furring strip/rigid foam approach (see image attached below). We were thinking that the ZIP System might be an easier installation approach than the sandwiched furring strips and overlapping rigid foam approach. Thoughts on this?
We’d like to finish things off with a vertical siding rainscreen. Are people still using a product like DuPont Rainvent mounted horizontally so that the siding can be mounted vertically? We saw that this is a recommended strategy in place of horizontal wood furring/strapping to avoid water issues.
I also know EIFS is probably the easiest and cheapest approach but that is not an aesthetic we are interested in.
Thanks,
-Scott
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Replies
A drainable house wrap would work. There are other options out there beside Tyvek.
I've had good luck with standard horizontal strapping with metal siding. It does limit airflow but it provides the all important capillary break. You can also bevel the top edge of the strapping to channel water away.
Another option is to go with reverse board and batten siding. This way the battens act as rain screen strapping, so you get vented cladding for no extra work.
Hi Akos - thanks for the response.
"A drainable house wrap would work. There are other options out there beside Tyvek."
-What are you referring to? Wrapping the existing masonry home exterior in a wrap? If we aren't using the Zip System for an integrated insulation/WRB, it seems like the liquid applied air barrier directly on the existing exterior masonry from the BSC article is the best way to seal it up.
"You can also bevel the top edge of the strapping to channel water away."
-It seems like this is a good compromise. I'll need to look more into this. I've also seen the strapping grid, which makes sense but is about 2x the material, which is less attractive.
"Another option is to go with reverse board and batten siding"
-Not a bad idea, will look into this as well.
I've been researching exterior masonry retrofits for a while now and it unfortunately is super uncommon. I wish there were more answers out there besides the BSC pilot project.
Thanks again,
-Scott
You only need one WRB over the masonry. In case of ZIP, that coating on it will suffice. The drainable house wrap would go over the zip, depending on the brand it might include an extra redundant WRB (nothing wrong with that extra layer).
Make sure the windows are flashed to the ZIP WRB, you don't want any bulk water making it between the zip and the brick. The grooves from the brick do offer a bit of drying capacity but not a lot, with an interior vapor barrier, I would make sure the foam only goes onto dry brick.
A fluid applied WRB over the brick would help to seal it up, I'm not sure how much and if it would be worth the extra effort.
Usually most masonry is insulated from the inside as most people prefer the look of brick. Around me, the only thing I've seen installed over old brick with any R value is EIFS.
No one out there on Green Builder Advisor has recommendations/experience with an exterior insulation retrofit on a masonry building?
Not encouraging....
Martin wrote about this kind of project here: Exterior Insulation over Masonry Cladding.