Assembling foam panels?

[MushCreek]

I finally found sort of a deal on foamboard. The plan is to attach it to the ceiling trusses, then put tin over (under) it for a finished ceiling. Here's the catch- the foam panels are all 4X4X2-1/4". My thought is to put up a double layer, getting me close to R-25. I'm thinking about assembling bigger panels on the ground prior to putting them up. Maybe 4X12X4-1/2" thick, with staggered joints for improved air sealing. An assembly that size is about 32 lbs., which I think I can handle. The alternative of course is just putting one 4X4 piece at a time up there. I plan to use construction adhesive and looonnng screws, through a plywood washer to hold the foam up while the adhesive dries. I'm assuming that after the adhesive cures, I can remove the screws and reuse them. I'll use the same screws to put the tin up.

The way my ceiling is built, it would be tedious to do other types of insulation. The joists are on 12" centers, which means a lot of cutting and fitting. An alternate would be to staple up geotextile and have cellulose blown in, but my shop is jammed with stuff, so it would cost me a lot more to have the insulation guy come out three different times while I move stuff around. Emptying the shop is not an option. My ceiling joists rest on top of triple 2X10 beams. There are three bays. To insulate the spaces between the joists would involve insulating 84 separate spaces. I think the foam board would be the easiest path. With the loft above, I think R-25 is plenty for non-living space. I've found that the space stays reasonably comfortable much of the year without HVAC, with only mid-winter and mid-summer getting really bad. I plan to put in a minisplit for that. Plans for the 2X6 walls are R-19 batts.

I'm in upstate South Carolina, so we have tolerable temperatures much of the year.

 

[jack stand]

Can you work from above?
Cutting and fitting (and foaming the edges and seams) isn't all that bad if you pre "ripped" the foam down to 11" and pushed it down on to your already installed metal ceiling.
I may have missed reading where there's already a floor above but that's probably the case and the reason for the 12" o/c framing.
There are long hex head screws and plates that are used in commercial roofing to secure foam insulation on a steel "pan".
I could see where just 2 of these and possibly just 1 would hold up a 4x4 section, at least on the first layer. The 2nd layer might require more but gluing and removing the screws is something that I wouldn't consider.
What type of foam is it?

 

[MushCreek]

Polyisocyanurate, whatever that means. No access from the top. The loft floor is sheathed, and has a lifetime's worth of stuff stored up there. 2" foam is pretty rigid, so I don't think it would take a lot of screws to hold it. My biggest concern will be hitting a 2X joist after driving through 4+ inches of foam. It wouldn't take much of an angle to miss altogether. I might make some sort of jig so I can drill a pilot hole nice and square. I figure the tin ceiling will hold everything in place, but I have to keep the foam in place long enough to hang the tin, which may not happen right away. Yes, I know foam burns, but so does wood, and the entire inside of the building is exposed wood anyhow. By the time flames reach the 12' ceiling, the place would be a total loss. I could rip strips and wedge them in from underneath, but there's wiring in the way, plus ripping the material is just an added step. I don't mind losing the ceiling height. I've even though about dropping the ceiling height in the two side bays, as I don't need the height there, and it's just added area to heat/cool. But then there's the added cost of framing the drop ceiling. I'm trying to do this as cheaply as possibly. I live on SS, so the wallet is rather slim.

 

[racecougar]

So this ceiling will be under a loft, not under an attic, correct? I assume the loft is fully closed in? Trying to picture what you've got going on.

 

[cgrutt]

I'm by no means an expert with this stuff but have been researching insulation for a potential upcoming project. Note the R-value of polyiso fluctuates with temperature, particularly below freezing. So you may not be getting the full R-value you think you are getting when you need it the most. Probably not that much of an issue in SC but something to think about.

 

[firebirdparts]

That sounds like it'll work, but boy, those are going to be some long screws. i'd probably try it if I was in your situation.

 

[thomfr]

Check please if they are rated as fire resistant as not all are and these are not allowed to be used for insulation.
Thom

 

[BillK]

Personally I would get some 24" wide fiberglass and cut it lengthwise to fit in your stud bays. It should hold itself in place long enough to put the ceiling panels on and be done with it. I bet you could probably even find 12" wide fiberglass if you looked a little. Maybe ask a local insulation contractor.

I am all for saving a few bucks but by the time you buy the construction adhesive to do what you are describing it will probably be a wash.

Also, like a couple of others have mentioned, a picture would certainly be worth a thousand words in this case.

 

[MushCreek]

I guess I could do a quick Sketch-Up of it. I have drawings, but they are stored away...somewhere. Basically, it's a 28X28 room with a 12' ceiling. The loft overhead is enclosed. There's a stairwell up to the loft, but it's closed and insulated. I guess at this point it's an attic. There's a big sliding door at one end, and the other end is insulated, as it's a wall that leads into a finished great room on the other side. Closing that wall made a big difference in how comfortable it is in there. I have a 17K BTU electric heater, and it is able to raise the temperature some, but of course, the electric meter is spinning like a Frisbee. The walls are 2X6 studs on 16" centers, sheathed in T1-11. I'm thinking about getting a heavy plastic curtain to minimize the heat loss through the sliding doors. Right now, there is one man door outside, and no windows. I do want to add a couple small awning windows up high to let in natural light. When the power goes out, it is DARK in there.

What I'm going to have to do is move everything out of one bay, insulate and finish, then move everything back. There are three bays; two are about 7' wide, the middle one is about 13' wide. That's why I can't hire out cellulose, or even DIY because of the time factor of moving everything.

 

[BillK]

I guess I could do a quick Sketch-Up of it.

I mainly meant a picture of the ceiling. I wanted to see the spots where you would have to put the insulation.

 

[MushCreek]

OK, here's a shot of one of the side bays, and a sketch of the cross-section of the barn. The attic is not insulated. It's on an uninsulated concrete slab. When the whole barn was open, it used to get well below freezing in there. Now, with the loft enclosed and one wall insulated, it rarely gets below 40.

 

[mike93lx]

I think I'd rip the boards down on my table saw to fit between the joists. It would be a lot simpler working solo.

Push them up into the bay, seal around the edges with spray foam, then add your ceiling

Since the loft is insulated, the benefit of cutting down on thermal bridging is less significant, so I think I'd prioritize ease of install.

Has the added benefit of not messing with super long, and expensive, screws overhead

 

[BillK]

Is the loft insulated ? If so I don't know if you will really gain much of anything by insulating the ceiling.

 

[BobnCO]

FYI I ran Polyisocvranate insulation through my table saw and immeadiately felt like I had been beathing glass shards! : ) I put on a dust mask and finished... but I made a mess in my work area (and I'm not particulalry picky) I liked the "purfect peices" to fit where I needed but made a point to cut outside and with a mask in the future!.

I have seen those 4' x 4' x X" Polyiso blocks before, they are ussually take offs (or over ordered) from flat membrane roof installs. They can be a good deal!

Bob

 

[mike93lx]

FYI I ran Polyisocvranate insulation through my table saw and immeadiately felt like I had been beathing glass shards! : ) I put on a dust mask and finished... but I made a mess in my work area (and I'm not particulalry picky) I liked the "purfect peices" to fit where I needed but made a point to cut outside and with a mask in the future

A mask and at least a vac connected to the saw are a must for this

 

[racecougar]

From posts #9 and #11, it sounds like the upstairs attic or loft is not insulated, so insulating the floor between makes sense.

I do agree with the "fill the cavity" rather than "below the joist" approach. Dealing with the foam boards, especially with having to move things out of the way in the building, will be a PITA, IMO. I'd use batts. You can batt and sheet a section of the building at a time easily.

 

[cvairwerks]

I'd just have the spray foam guys come in and do it. You've already got a number of obstacles that would require a lot of time to cut in around. The spray guys would be in and done in a day or less.

 

[pima67]

Rather than cutting strips with a saw, there are electric foam cutting tools available,

 

[mike93lx]

Rather than cutting strips with a saw, there are electric foam cutting tools available,

I dont think a hot wire will work with poly iso. You could use some sort of reciprocating knife or band saw. The table saw had the benefit of a large fence, though

 

[PCustoms]

I'd just have the spray foam guys come in and do it. You've already got a number of obstacles that would require a lot of time to cut in around. The spray guys would be in and done in a day or less.

This.

Polyiso sheet isn't very cheap, might be surprised by the cost savings of having it sprayed.

 

[MushCreek]

The loft isn't insulated. As for having it foamed, I mentioned that there is a lot of stuff in the way on the floor. I'd have to have them come in three different times, which I'm sure would add to the cost significantly. The poliso would be about $1 a square foot. Batts would be similar. I made the mistake of moving in before the shop was done. I've been living with it for 12 years now. What is there to be moved? Machinery, shelves full of stuff, a hanging wood rack, workbenches, cabinets, and a lot of car and tractor parts. I can't move the stuff outside in the weather. I have to take down one wall of pegboard so I can insulate behind it. This is going to be a long project because of all of the stuff in the way. I'd like to clear out one bay at a time, insulate the ceiling and wall, and put finished materials up before moving on to the next bay. At least the center bay doesn't have any wall area to be done.

 

[PCustoms]

The loft isn't insulated. As for having it foamed, I mentioned that there is a lot of stuff in the way on the floor. I'd have to have them come in three different times, which I'm sure would add to the cost significantly.

I'm lost...they'd come in and spray from below. I thought you were referring to stuff on the floor above earlier?

 

[cvairwerks]

A good foam crew would simply cover things and spray.

 

[mike93lx]

Get a quote on foam. They may be able to work around stuff better than you think

 

[Hank11]

Dead easy to cut Rockwool batts to size and push them into the joist cavities. Buy the batts for 24” center framing. Cut them long ways with a bread knife. Its incredibly easy. Beyond easy. You’ll be done in no time. Then screw up your ceiling.

Buy as much rockwool in one trip that you can carry or put up that day or half day or have room to store. Put it up when you have time.

 

[MushCreek]

Around here, Rockwool is twice the price of fiberglass. Post #3- I live on SS, so the wallet is rather slim.

 

[Mr onetwo]

Unless you already have purchased the foam...don't do it.Save yourself the misery of dealing with that stuff. Check out Knauf fiberglass.They have many forms of fiberglass batt that is made for 12" oc construction and there is a distributor in Spartanburg.I would give them a call.Put up a layer of un-faced held up by supports.Then another layer of kraft stapled up. Much easier. Cover up with a hooded throw away Tyvek suit and a mask.Put a bit of corn starch on any exposed skin and Bob's your uncle.

 

[E1271]

It sounds like budget friendly is the most important driver of the decision process, next sounds like ease for 1 person to do sections at a time. Cut down the foam you have to fit between the joists. You'd just have to make a seam wherever you have wires but you'll have plenty of seams anyways.

Attaching the foam to the bottom of the joists is possible, no doubt. Hitting the joists with long screws would be my only concern.

It sounds like a wore out shoulder kind of project either way though. The foam board isn't the best option but in this case, it'll work fine just make sure you have some advil, aleive, or beers to help forget the soreness!

Good luck, post an update when you get started!

 

[MushCreek]

I'm not getting the 'misery' of dealing with foam panels? Light, and doesn't give off itchy or dusty particles. No need to suit up. Can be cut precisely if desired. I'm wondering if one of those so-called 'instant grab' adhesives would be strong enough to hold it up until the glue cures? It would be worth experimenting with a $5 tube. I just read about polyiso, and it doesn't sound too bad. The main drawback is that it's more expensive than other foams, but I have a deal on it. It shouldn't be used below grade, but I'm 12' away from grade.

I also don't see the advantage of ripping it and putting it in between the joists. I doubt the joist spacing is all that accurate, so I'd have to custom cut each bay. If I attach it to the bottom of the joists, it also eliminates thermal bridging from the loft. My whole house is foam (ICF), so I'm well acquainted with working with foam.

 

[Fixr]

I'm not getting the 'misery' of dealing with foam panels? Light, and doesn't give off itchy or dusty particles. No need to suit up. Can be cut precisely if desired. I'm wondering if one of those so-called 'instant grab' adhesives would be strong enough to hold it up until the glue cures? It would be worth experimenting with a $5 tube. I just read about polyiso, and it doesn't sound too bad. The main drawback is that it's more expensive than other foams, but I have a deal on it. It shouldn't be used below grade, but I'm 12' away from grade.

I also don't see the advantage of ripping it and putting it in between the joists. I doubt the joist spacing is all that accurate, so I'd have to custom cut each bay. If I attach it to the bottom of the joists, it also eliminates thermal bridging from the loft. My whole house is foam (ICF), so I'm well acquainted with working with foam.

Using adhesive, you might be able to hold the panels up with spring boards or similar while the adhesive sets.

 

[PCustoms]

I'm not getting the 'misery' of dealing with foam panels? Light, and doesn't give off itchy or dusty particles. No need to suit up. Can be cut precisely if desired. I'm wondering if one of those so-called 'instant grab' adhesives would be strong enough to hold it up until the glue cures? It would be worth experimenting with a $5 tube. I just read about polyiso, and it doesn't sound too bad. The main drawback is that it's more expensive than other foams, but I have a deal on it. It shouldn't be used below grade, but I'm 12' away from grade.

I also don't see the advantage of ripping it and putting it in between the joists. I doubt the joist spacing is all that accurate, so I'd have to custom cut each bay. If I attach it to the bottom of the joists, it also eliminates thermal bridging from the loft. My whole house is foam (ICF), so I'm well acquainted with working with foam.

You planning to buy used roofing panels?

 

[larry4406]

Can you use insulation spring wire to hold the foam in place till you seal it in? These are normally use for batt insulation but will hold up your foam if it is not snug to the joists.

 

[PCustoms]

Can you use insulation spring wire to hold the foam in place till you seal it in? These are normally use for batt insulation but will hold up your foam if it is not snug to the joists.

I was thinking of these too, but how will this work if he's applying to bottom of joists?

 

[larry4406]

I was thinking of these too, but how will this work if he's applying to bottom of joists?

Perhaps I mis-read that he wanted to insert it within the joist bays.

If he is applying it to the bottom of the joists, then just screw it up into position using a larger fender style washer.

 

[Hank11]

Around here, Rockwool is twice the price of fiberglass. Post #3- I live on SS, so the wallet is rather slim.

Not made of money here either.
Add in the costs of all materials to see what the total installation costs are. I bet you can buy rockwool and poke it in the holes — cheap and easy as anything when you add up the other stuff you need to use the cheap foam. And you can spread the purchase over time.

 

[Firstram]

If you do use the foam, consider installing 1x3 battens 4 foot on center. This would give you a substantial and predictable screw pattern for the sheet metal. On top of that, you won’t have to struggle with stupid long screws while holding the panels up!

 

[MushCreek]

Ah- put the 1X3's up before the foam, giving you a much bigger target for the screws. The panels I sourced are new, not used.

 

[Firstram]

No, after the foam. That way it’s easy to make the finished ceiling look good! Who cares what the foam looks like!

 

[jack stand]

I was going to mention about putting up the 1st layer with a few screws or 16d common nails, then install some combination to get close to the 2.25" thickness of the foam (2x4 and a 1x3) flat for the bigger target to hit on 4' centers across the floor joists then set your 2nd layer in between this glorified strapping. It'll be more forgiving to a miss hitting the joists. It'll be under the metal so you can just back out the screw and try again. At that point you'll be able to see the strapping and use normal washer head and paint matched screws. A row of screws every 4' will be fine for a ceiling.