Seal 6″ penetrations needed for installing ERV
BradTW
| Posted in General Questions on
Hi – I am investigating ERV units for our existing house, and I have a question on how best deal with the 6″ penetrations that will be required for the fresh air in and exhaust from the unit. The exterior cladding is brick, sheathing is ZIP, and then foam insulation between the 2×4 studs. Are there best practices and/or recommendations on venting accessories and methods to seal the penetrations in a retrofit scenario such as this?
Thanks in advance for the help.
Regards,
Brad
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Replies
Brad,
The trickiest part is drilling the holes through the brick veneer. Once you manage that, the rest is relatively easy. You'll probably be relying on high-quality caulk and canned spray foam to seal air leaks.
You can get 6" diamond-grit hole saws suitable for drilling brick if you have a, low speed drill motor beefy enough to handle it. eg: http://www.starrett.com/metrology/product-detail/KD0600-N (A Milwaukee Hole Hawg drill motor would do it- might even be overkill, but your typical 1/2" chuck variable speed hand drill isn't the right tool.)
If the hole really needs to be 6.5" , not 6.0" you'll probably have to do something else.
Brad, assuming your WRB and airtight layer is at the sheathing, simply drilling a hole through the brick won't give you enough space to do the necessary sealing around the penetration. I would remove bricks around the penetration, cutting through the mortar with a masonry blade, and clean the bricks for re-use. (Hopefully they used mortar softer than the brick, which is best practice but not all masons follow that rule.) Then use tapes or gaskets to seal the duct to the sheathing and/or WRB. Most builders use tapes (https://www.greenbuildingadvisor.com/article/air-sealing-tapes-and-gaskets) but gaskets are faster and possibly more reliable (https://foursevenfive.com/products/air-sealing-system/duct-pipe-wire-penetrations/?sort=featured&page=1).