Best Method for Air Sealing This Wall Assembly
the74impala
| Posted in General Questions on
Northern Wisconsin zone 7
Pictures attached. Trying to air seal this wall. Outside has D Log, and framing/flashing. Sheathing is combination 1″polyiso sheet and in some places 1/2″ plywood. Red squirrels in the yard, impossible to stop, but would like to give them a challenge to get in.
Anything besides sprayfoam? I have tried 1/2″ plywood with pocket screws in the 2 spots shown. Hard way to go.
Any thoughts would great.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
A few more shota
Not the easiest setup you have there. The 1" of polyiso on a 2x4 frame isn't all that much in Zone 7. Ideally you want about 2x that outboard. How thick are your D logs on the outside. 5" or so would add a enough R value to get the assembly to work much better. If less than that, you would also need a warm side vapor retarder.
No easy way to seal that from the inside. You can try taping all the seams and caulking around joist bays. Realistically, SPF is the easiest option. You can flash the cavity with 1" of closed cell to seal it up and install 2.5" fiberglass rolls to fill the rest of the cavity.
Instead of trying to seal, you can also look at dense packing the walls combined with air tight drywall as your air barrier. Dense packing does a great job of restricting air movement, combined with a well detailed drywall air barrier would go a long way for air sealing.
As for keeping critters out, you need to deal with that on the outside. Instead of continuous air barrier, think of it as continuous critter barrier. There can't be any gaps along the exterior anywhere. This generally means wire mesh at corners/intersections and stuffing steel wool around the rough openings. SPF does nothing to deter critters. For some critters, plywood is enough, some require wire mesh. You can try to do this from the inside, but it won't keep the critters out of the foam.
It had fiberglass and poly before. No mold, but lots of bugs and rodents.
I didn't find any mold, but lots of bugs and rodents.
Would BIBS with fiberglass work? I can tape/caulk/can foam all the obvious openings, but some spots seem impossible.
Lots of bugs means gaps somewhere to outdoors. Rodents means larger holes, possibly chewed passageways. Bugs can usually be dealt with with a tight assembly, normal air sealing keeps most out except for the boring kind that tunnel in things -- those guys will chew through foam.
Rodents chew things. If you have an issue with rodents you need metal flashing or mesh as Akos suggested. Window screen is no usually strong enough, you need hardware cloth. 1/2" mesh is usually enough, but 1/4" mesh is MUCH better. Use the mesh to make a barrier over and around whatever your want to protect. I've often put mesh in place and then spray foamed over it. The spray foam locks the mesh in place, and makes the foam impenetrable to critters -- they can only chew a little of the foam before the mesh stops them. If you do this, you want the mesh towards the exterior side of your spray foam layer for maximum protection. If the foam is going over framing or sheathing, you can tack it up with a staple gun. The fastening only needs to be secure where the critters can pull at the edge, in the rest of the areas it's not as critical that it be tightly fastened.
Note that aluminum mesh tends to rot out quickly when near the ground in many areas. Galvanized steel is better, stainless is best. Welded mesh, as opposed to the kind that is only woven, is also more durable since the individual wires are locked in place and can't be slid around by persistent critters. You can also use sheet stock, but then you have a vapor barrier which might be an issue in some locations.
Critters usually get in around the edges of things, so that's where you want to focus your critter proofing efforts -- edges, seams, and corners.
Bill
Most critters/bugs will happily live in insulation, BIBS is not going to keep them out.
Borate treated cellulose is bit more resistant to some critters, might be a better option in your case.
Either insulation, dense packed, will go a long way in tightening up the house.
I would also re-install the vapor barrier. One of the smart vapor barriers would be a better option. A well detailed vapor retarder also makes for a decent secondary air barrier.
It is also good to replace your electrical boxes in your outside wall with vapor/air tight ones (ones with a flange) while the wall is open. Much easier than trying to air seal standard device boxes.
+1 for air sealing electrical boxes.
If you don't want to, or can't use the flanged type for some reason, the second best kind of electrical box to use for air sealing is the so-called fiberglass "hard box". These are usually white, and they have NO HOLEs. You have to poke out thin spots for cables to enter. These are much easier to seal with conventional methods compared to regular plastic or metal boxes.
If you are stuck with the existing boxes, careful used of canned foam on the back and red silicone high-temperature caulk around the wires and screw holes (if needed) will work, but is more labor intensive. Don't use intumescent caulk here, use the red high-temperature SILICONE stuff.
Bill
I had a new roof put on last fall. I had them use my 1/4" hardware cloth on the ridge which is where I think most of the squirrels came from previously.
I am building site built baffles out of 1/2" plywood to keep it as sturdy as possible. They say they follow the smell, so hopefully if there is no smell to lure them, they won't try as hard.
I'll see if I can get some more quotes for insulation. The last one I talked with doesn't do spray foam, but I think I need to consider that for this whole gable end as an option.
The D log is 5-8" thick, depending on where you measure on the D.