Detailing holes through a double-stud wall
Hello everyone, I’ve been lurking for a while after I’ve bought and read PGH.
I finally jumped in and decided to go for a PGH in Quebec/Canada, CZ 6.
My GC and building team so far have been very interested in the build and we managed to get someone skilled enough to blow cellulose in our double-stud wall (r4-2×6″-3.5″-2×4″). Now everyone else, plumber/ventilation guys/Heatpump people have started poking holes everywere.
I’ve been looking for some details about how to properly inspect and patch holes in this type of construction without success. Does anyone have some details about the common holes and good practices?
So far:
-> Intake and Outake of our HRV
-> Range hood hole
-> Plumbing vent
-> HVAC guys holes to connect the exterior unit
-> Electric wiring for exterior lighting
-> Probably missing a few
I intend to have a blow door test soon and would like to future-proof the openings, since some contractors were not sooo familiar with a double stud construction. Altough everyone has been really interested in the build and taking great care so far.
Thanks in advance for your support!
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Replies
Following along to see some wisdom from other members.
Eledmackey,
The holes need patching in two different ways. They need to be sealed against air-leakage, and detailed at the exterior to avoid water intrusion. I'm not sure the way you do that is much different in a double-stud wall than it is on other more common ones.
How and where you air-seal penetrations spends on where your primary air-barrier is. If, as is common in Quebec, the air-barrier is interior poly, then they gets sealed and taped to it before drywall. If it is the exterior sheathing the sealing occurs there. Once that is done it doesn't matter what occurs elsewhere in the duct, pipe or wire's path through the thick wall.
Exterior detailing of terminations to stop water intrusion gets done at the WRB and cladding. That detailing is pretty much the same on all walls independent of how thick they are.
Thank you Malcolm, quite happy to hear there isn’t something special to think about.
Indeed, people working on the house so far have taken special care to seal the poly and wrb thoroughly.
I was quite amazed at my hrv team, they made a 8” hole with a duct, properly sealed to the wrb and poly and then inserted a 6” insulated intake/outake in those pipes. My GC was a little worried about future condensation between both duct though.
Thanks again!
I have been using this Interra MAP system and really like them for sealing both to the WRB and inside to the vapor retarder https://interra-usa.com/sealer-tapes/#sealer__sc1
https://www.youtube.com/watch?v=4eD8tNeFzG4&t=13s
Really interesting, thank you!
That is pretty slick. Thanks for sharing. Adding that to my notes fo managing penetrations this summer.
I am not affiliate and get no kickbacks. But I can say, ordering them online before a job and getting them in the mail a few days later saves me more time than trying to track down roofer for epdm. Also had good success with applying in fairly cold temps this spring.
If your builder has a scrap of epdm rubber roofing it’s simple to make a custom gasket on site. Cut the penetration hole undersize and leave a couple inches outboard. This then gets sealed to the wrb with tape and/or liquid flash.
Heat pump linesets through walls can be sleeved in 3” pvc pipe which is then sealed to the wrb. After installation a bit of gun foam seals the lineset in the pipe.
There are some nice details in this build blog (click on view gallery):
https://www.greenbuildingadvisor.com/article/flatrock-passive-air-sealing-the-penetrations
Awesome ressource, thank you!
Edelmackey,
To add to Ako's link:
https://hammerandhand.com/best-practices/manual/5-envelopes/5-1-wall-penetrations/