Are you looking for sound isolation primarily? I know lots about sound isolation.
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Sprayed insulation: when you want to make future work a complete fucking nightmare. Also great for hiding damage which will be even more difficult to repair later.
Yes. Worked well but burns through cans. So overestimate for your project or look for industrial size application canisters if a larger project. No idea where. And would recommend a tyvek suit and a good face mask. Also difficult to get a desired thickness if R value is important
Even pros fuck houses up with spray foam. It can trap moisture and lead to massive problems with rot and mold.
I'm much cheaper than that... I did 2" foam board and then those kind of cans to seal around them.
Foam board was cut into pieces roughly and inch shy of the cavity dimensions... E.g. 14*5 for a 15x6" opening. Once the foam adhesive set (e.g. following weekend) I sprayed around the edges to seal it in.
I had to get a 30" gun adapter to do it which requires cans that can be attached to a gun. The ones that can't may not have the reach to get you into the cavity.
If you have full access to the cavity, that dap kit someone else sent would be my go-to... I didn't have the immediate access or will to do it all in one go... There were unmentioned complications in my way requiring lots of prep work.
E: Code likely requires a fire block between the living space and the foam. Afaik drywall, rockwool, among others count.
What’s the foam adhesive you mentioned? You describe it I think as holding the foam board in place?
You can buy it bulk way cheaper.
Something like this maybe? I've used a two-part system like this before to insulate/vapour barrier between the joists where they meet the foundation wall and it worked decently for that.
If you're doing the whole ceiling though I'd go for batts of some kind or hire a spray foam company.
How thick did you go for that? I need to do that before winter.
Cheaper alternatives?
My understanding is that it's best to use spray foam here because it's an outside surface you're insulating from inside, so moisture will condense there unless you seal it.
As long as there's something acting as a vapour barrier you'll avoid condensation, it doesn't need to be spray foam. You want vapour barrier in the warm third (by R value, not necessarily thickness) of the wall to avoid condensation. So hot places that mostly run AC will have their vapour barrier to the outside off the wall, where cooler places you tend to heat is the opposite.
You can do the joist ends with batts and poly, it's just really hard to get a good seal especially with I-joists. I think the foam stuff is R5 per inch? Might be a bit better than that but was targeting R20 so 4" inches thick, maybe a bit thinner if it's R7 per inch. R value is a measure of how well something resists heat transfer btw, higher number is better.
Check how things are built in your area as it can be very regional depending on climate and building codes.
Thanks.
Yeah we're on the edge of zone 5/6, so fairly cold in the winter, we do more heating than cooling, and a high r value is desirable.
I did some research after posting my question, and it seems like a cheap way to get sealed and high r value is to do what you said and cut poly to fit, and then seal the edges with spray foam. But then instead of doing more layers of that, just put a few inches of unfaced batting on top to boost the r value. I'll probably go that route, do the whole basement for $50-75 instead of $500.
You'll probably want the batts in first before the poly to get the vapour barrier on the warm side, but yeah spray foam isn't cheap so it's best used for spots you can't insulate conventionally.
There's the added benefit of making future work easier if you don't need to chip out a bunch of foam to run a new wire for example.
Hmmm, I see the logic of warm side cold side and condensation. I just can't get my head around the idea of creating a type of vapor barrier and potentially sealing moisture between the joists and outside plate like that.
Not saying you're wrong, just thinking out loud. Thank you for your input!
That's quite a lot of cans there. What are you trying to do? Thermal insulation or sound deadening?
If thermal insulation, Great Stuff is typically the default option. I would also supplement with closed cell foam insulation boards.
At a bare minimum you will need a foam cleaning solvent can to keep the gun from clogging up. Wear disposable gloves. Keep rags nearby. If you make a small mess, wait for it to dry before attempting to clean it.
First of all why do you need it
Second of all don't buy fire barrier products from Amazon, your local hardware store or electrical supplier will have correctly rated and fresh product.
If you are doing this work as a contractor, get any building inspector you've met to tell you about the products they approve for this.
I need to insulate my basement ceiling and rim joist bays on a short budget.
Oh this will not fill as much volume as you need. This is for plugging holes into a garage or through some other fire rated wall.
Rockwool insulation held up with string, and then poly sheeting stapled over that is probably the cheapest way to do it correctly with a high R value... Idk though I'm back to asking an inspector what they would accept, but I work construction so I speak to them. Your hardware store randos will point you in a better direction than me probably.
Don't believe the coverage claims, it's always much lower.
Also, Rockwool is a brand name of the generic mineral wool. There are other, cheaper brands of mineral wool, than rock wool and they work just as well.
That's really interesting to me that they use "board feet" for the coverage. For lumber, board foot is a very specific measurement that means a square foot, one inch thick (so 144 cubic inches). The insulation value is then measured at 2" thick. Unless DIY spray foam means something different by a board foot then coverage is going to half the area at the advertised R value, and roughly a third if you fill in the 2x4 framing cavity.
Professional spray foam is pretty expensive, but it's probably a way better idea than than this DIY stuff. The mineral wool is probably fine, and I would happily let somebody punch me in the stomach if it meant I didn't have to mess with fiberglass batts.
that was a good video, and the followup one too
those guys have good video presense. I will keep them in mind next time I need a video like this. Thanks!
Great video! I need to do a basement ceiling and rim joist bays and the budget is tight. If you know where I can order the other brands of mineral wool, I would love to know too.
I don't recommend spray foam for a number of reasons, a few being that it offgasses VOCs after installation and can obscure or make future access to repairing surfaces impossible. If, for instance, water in your bathroom seeps into your subfloor, that repair becomes suddenly infinitely more complex if you have to fight through spray foam.
I highly recommend mineral wool batts, even if you do thin ones. They can be cut with a thrift store bread knife/any serrated knife and friction fit between the joists. Very easy install for an amateur, very forgiving. Save the spray foam for those tricky gaps next to doors and windows.
We bought ours from a local contractor supply store, and it was cheaper than Orange or Blue store and they delivered for free. Not sure where you're at but search around.
As said previously, purchase locally. And also don't consider spraying this into the tailpipe of an ICE (Internal Combustion Engine) vehicle.
I have done the rim joists in my basement using a similar spray foam product. The biggest recommendations I have are:
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Use the kind of gun pictured and not the cans that come with a straw. It is much easier to apply consistently and you can actually stop work and start again the next day using the same can. The straws work OK but they always get clogged when you stop for a bit so only use them if you are working on a small area and plan on using the whole can in one go.
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Look into the difference between closed cell and open cell foam. I've never seen closed cell come in a can like that so I'd bet money that is open cell foam. It works great for air sealing but you need to apply a ton of it to get an appreciable R-value. Closed cell foam is a lot more expensive in the spray form and is a 2 part mixture that is more complicated to work with.
What I ended up doing was buying some 2" closed cell foam board at the local hardware store. It's relatively cheap in board form and is easy to cut. I cut a piece of the foam board to fit inside the rim joist space and then used the spray foam to air seal both the rim joists themselves and the small gap around the foam board. I think this is the most effective way to do it unless you go for the 2 part closed cell spray foam but that was more than triple the cost of the foam board + open cell spray foam.
For comparison, the 2" foam board has an R-value around 8 and, if memory serves, you would need something like 8" of open cell foam to provide that same level of insulation. You can get an equivalent R-value with 2" of the closed cell spray foam but last I checked the spray stuff was about $800 and an 8'x4' sheet of 2" foam board is around $60.
This is the correct answer. Or use old school pink insulation.
One newer alternative my contractor used is timber hp, its physically like a block of firm tofu so you take the chunk/board and muscle it into the joists and it just stays. Its cool but cutting it looked miserable.
The current bottle has been attached to my foam gun for well over a year. I only need a little bit every few months or so. After use I just close it and clean the tip. Previously I always removed the bottle and cleaned the gun after each use and they'll stop working in less than 6 months.
I'ved used fire rated spray foam, but not that kind. Its a messy task and I would prefer the kind that doesn't require cleaning the nozzle gun. If you don't clean it propperly I imagine it will become an expensive nightmare.
This is for sealing gaps, not doing large areas. You take a board of insulation, cut it a little smaller than the gap you put it in and then with this you seal the edges and glue it in place. It's completely different than the expanding foam you've possibly seen people spraying between joists on YouTube. This is more like a caulk gun.
Yes, 10 years ago when I bought the house and brought the internet cable inside. No problem, never had to change it. No idea what brand it was.
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