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Dr_1400
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# Posted: 19 Jul 2020 09:25pm - Edited by: Dr_1400
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Hello,
Our log cabin in Upstate NY currently has rigid foam insulation covering the entire underside of the cabin (i.e., not just between the floor joists). Cabin sits on piers/posts. The crawlspace offers enough room to work. There is no skirting of any type, so the entire crawlspace is exposed.
The old foam is falling apart in some areas, and we have a significant mouse population. I know we'll never beat the mice fully, but thinking that by shoring up the insulation issues we can minimize some access/habitat while perhaps keeping some more warmth in during the winter months (we use the cabin year round, with woodstove heat).
I've been thinking of three options:
1) Reflectix stapled between the joists, tight to the subfloor
2) Roxul stuffed between the joists, tight to the subfloor, with 1/4" hardware cloth stapled to the joists to cover the entire area
3) Shoring up the foam sections that have fallen down and then attaching the 1/4" hardware cloth to the bottom of the joists to cover the entire area.
I've been wading through the old threads today, but curious if anyone has experience or strong thoughts here. I understand we lose some heat through thermal bridging across joists with first two options, but presumably gain something in the rodent war.
Any thoughts?
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rpe
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# Posted: 19 Jul 2020 10:45pm
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We put R24 Roxul batts in from underneath, covered with a layer a house wrap, and then put the 1/4" hardware cloth over that. It worked out really well, and there have been no rodent issues so far. The house wrap does a great job of holding the insulation up and in place, and allows the hardware cloth to be installed without constantly grabbing and pulling on the installed insulation.
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rpe
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# Posted: 19 Jul 2020 10:46pm
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Under-floor pic
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Irrigation Guy
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# Posted: 20 Jul 2020 06:50am
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It’s expensive but could you get a guy out to shoot it with closed cell spray foam?
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Brettny
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# Posted: 20 Jul 2020 07:13am
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Refletex is R1..I wouldnt use that. I believe it's the same price as 1/2in foam board. Are you thinking of roxwool because the mice dont like it? I wouldnt use it for that. They will find a way in and once there in....
If the current foam is in Ok condition put it back up and spray foam around the edges of it. This method is called cut and cobble.
Any good insulation job can be destroyed by rodents if/when they find a way in. Try to really knock down the population, it's very hard to do this with simple snap traps. Also remember that traps in your building are baiting them into the place you want to keep them out of.
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Dr_1400
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# Posted: 20 Jul 2020 09:37am
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Thanks for the replies, much appreciated.
Quoting: Irrigation Guy It’s expensive but could you get a guy out to shoot it with closed cell spray foam?
I don't think that's an option in our location, unfortunately. At least not an option we'd be willing to pay for.
Quoting: Brettny Are you thinking of roxwool because the mice dont like it? I wouldnt use it for that. They will find a way in and once there in....
I was thinking Roxul because it's so easy to work with, primarily. We've used it in another home and thought it installed easily and worked well.
Quoting: Brettny If the current foam is in Ok condition put it back up and spray foam around the edges of it. This method is called cut and cobble.
I do think it's in Ok condition overall. None of the seams are taped, and there are pretty large gaps on the edges. So the material itself seems alright, just kind of sloppy. We do have an exposed shower trap to work around, as well as the waste lines. Any recommendations around those? The cabin's plumbing is gravity drained. When we drain the water in winter, the hot water heater, sink, and bathroom sink drain via copper stub lines right onto the top of the foamboard. The water finds it's way to the seams and drains down to the earth below. I was reassured by previous owner that the subfloor is PT plywood, but I'd still rather not have that situation. So extending those drain lines down below the insulation is another job.
Quoting: rpe We put R24 Roxul batts in from underneath, covered with a layer a house wrap, and then put the 1/4" hardware cloth over that. It worked out really well, and there have been no rodent issues so far. The house wrap does a great job of holding the insulation up and in place, and allows the hardware cloth to be installed without constantly grabbing and pulling on the installed insulation.
This makes a lot of sense, thank you. The hardware cloth grabbing on the roxul was a concern. Does your Roxul fill the entire joist cavity?
Quoting: Brettny Any good insulation job can be destroyed by rodents if/when they find a way in. Try to really knock down the population, it's very hard to do this with simple snap traps. Also remember that traps in your building are baiting them into the place you want to keep them out of.
Absolutely. I'm in the process of sealing the cabin as tightly as I can, hoping to limit entry. Right now it's a free for all. 1/2" gap under front door, gaps in fascia, etc. In the meantime they have particularly enjoyed an insulated ceiling over a bedroom. Next project is to rip out an attic floor to remove the fiberglass insulation there. At which point I'll have a separate insulation thread of questions 
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rpe
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# Posted: 20 Jul 2020 10:47am
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Yes, we completely filled the joist cavity wherever possible. Our cottage was not professionally built, so spacing varied a bit requiring some trimming and stuffing of the insulation. The stapled layer of Tyvek held everything in place nice and neat, as some batts would want to slide out on their own. Roxul is heavier than fiberglass, and also doesn't compress as easily, so we found some batts would want to slide out unless held up via the Tyvek.
We then unrolled the hardware cloth and used roofing nails to cover the floor as a rodent deterrent. We had 2 ft or more of clearance underneath, so it wasn't too bad of a job.
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Aklogcabin
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# Posted: 20 Jul 2020 11:44am - Edited by: Aklogcabin
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You may want to try putting some aluminum flashing on your posts to heap prevent them from climbing. Helps with other rodents also. Maybe put your insulation into the seams or gaps, have a piece of hardware cloth ready to cover the insulation in gaps. Spray foam insulation into crack and put wire into the still wet foam. You could use smaller pieces if it’s an awkward spot. Or use 1/4†square that the straw will fit through. Any tree branches that squirrels could jump from trimmed.
On your drain. I’m sure you recognize that you should find another way to drain. Can the copper drain pipes be accessed to be extended below the floor? Then maybe to a bucket so you can toss it. Then can it be boxed in ? This is done in the arctic. Or isolated from the rest of the project. Demanding different solutions. Trying to give you some positive feedback.
For what it’s worth, i still don’t have our floor insulated and it gets a bit cool here. But I’ll get there.
Good luck man
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SCSJeff
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# Posted: 20 Jul 2020 01:17pm
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Great Thread!
I'm in the same situation in central PA. Cabin on sonotube piers. No insulation at the moment.
Currently, no mouse problem inside the cabin. They do like to build nests in our grill and my lawn mower (which I keep outside).
We do have carpenter ants that I'm constantly keeping at bay. (they managed to start a nest inside the header above our deck doors during the construction)
Looking for inexpensive way to keep my feet a bit warmer in the winter (without inviting pests to make a comfy home too)
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Brettny
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# Posted: 20 Jul 2020 02:03pm
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How to mate foam board up to edges of boards and around plumbing...cut to fit with about 1/2in gap and use spray foam in the cans to seal up the edges. Very easy to do if the foam board is alreaty there.
PT sub floor shouldn't be needed as your sub floor should never see moisture once the building is dried in. I would fix what ever is leaking through the sub floor. Your growing mold if you dont.
Aluminum flashing around posts is a good idea!
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Dr_1400
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# Posted: 20 Jul 2020 02:51pm
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Quoting: Aklogcabin Spray foam insulation into crack and put wire into the still wet foam.
Thank you, will do this. By spray foam insulation do you mean something simple like Great Stuff?
Quoting: Aklogcabin On your drain. I’m sure you recognize that you should find another way to drain. Can the copper drain pipes be accessed to be extended below the floor? Then maybe to a bucket so you can toss it. Then can it be boxed in ? This is done in the arctic. Or isolated from the rest of the project. Demanding different solutions. Trying to give you some positive feedback.
Appreciated. The copper drain pipes extend below the subfloor. Prior to the insulation being added (foam board, nailed to bottom of PT floor joists), the pipes terminated about 2' from the ground. Previous owner did not extend those copper drain stubs when he added the foam board, instead allowing the water to simply drain onto the foam board and then work its way through the cracks in the board and eventually to the earth. He drained the cabin only once per year. We visit more frequently, and probably drain it 10x per year. So we're putting more water on top of that foam than he ever intended (not to defend the original design), and often in colder temps when it could ice up on top of the foam board before it works its way through the gaps between pieces of insulation.
So I think I'll start by removing the foam board from that section, extending the pipes down past where the insulation will go, and reattaching after creating a hole in the insulation for the new extended pipe to fit through. Then fill the remaining small gap around the copper pipe. (Great Stuff? Silicone?)
Quoting: Brettny PT sub floor shouldn't be needed as your sub floor should never see moisture once the building is dried in. I would fix what ever is leaking through the sub floor. Your growing mold if you dont.
I wasn't clear before, nothing leaking that I'm aware of. Only water that goes beneath subfloor is during intentional draining of the water system in the cabin.
Quoting: Brettny How to mate foam board up to edges of boards and around plumbing...cut to fit with about 1/2in gap and use spray foam in the cans to seal up the edges. Very easy to do if the foam board is alreaty there.
Sounds like I just need a few cans of Great Stuff and some time under the cabin to address the edges and plumbing. Appreciate the tip.
I think I'll try to shore up the foam board, spray foam the gaps, and then hardware cloth the entire thing. Only pain in the butt will be cutting the cloth around those plumbing traps and drains.
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old243
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# Posted: 21 Jul 2020 08:55am
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we used , used roofing steel under our hunt camp, had a big problem with porkupine's chewing the plywood sub floor. Added 2 inches of pink styrofoam to top side of the floor. strapped the floor, added foam sheets between . Then a second plywood floor above that. Has worked out well. Rodents are almost impossible to keep out, bucket traps are very effective. old243
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KelVarnsen
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# Posted: 21 Jul 2020 09:52am
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Quoting: SCSJeff I'm in the same situation in central PA. Cabin on sonotube piers. No insulation at the moment.
My cabin is up on piers. I found 3" rigid foam insulation used from a local scrap dealer. Apparently they have a supply frequently because some industrial and school roofs use it. It was priced way better than new.
Anyhow, I did the old cut-and-cobble method. It was a huge pain because none of the joists were installed squarely. I did detailed measurements of each joist bay, then cut custom pieces for each on my table saw at home and labelled them.
There was already some plywood holding up a small amount of pink fiberglass. I pulled the plywood off, got rid of the old insulation, put in the foam board and reinstalled the plywood. Toasty warm now.
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Carl Martin
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# Posted: 17 Aug 2020 02:16am
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Which one did you choose?
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