Shop ceiling - Victim of my own cheapness

Don't they have to spray the foam onto some backing (like a wall or under an upper deck)? About half of my top floor is decked but the other half is open to the attic area (except for the drop ceiling). Even on the part that is decked over they would have to shoot it through the grid, which would be tough I think.

I'm pretty sure that I would need both an air-flow barrier and insulation to be effective at blocking off the upper area. It would be no fun at all to try to push batts up into the joists through the grid.

Closed cell foam?? Is that the styro-foam-like board stuff?
 
Apparently there are insulating 2x4 tiles that can be used. They have an air barrier and insulation. About $4K worth of them...

Or, maybe this. R13. I have 2' on-center joists, I think I can tight-fit these between the joists and maybe tape the seams. It would leave open the possibility of putting batts on top if needed for greater R. Would cost about $1500 or so.

Big mistake or "might just work"?

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Closed cell foam is a two part system similar to Great Stuff polyurethane foam. It is closed cell. When it is applied, the excess is usually removed mechanically. It is arguably the best insulation but not the cheapest. If you spray it in, any future modifications will require cutting and removing foam. Although LED fixtures don't develop a great deal of heat, there is usually a requirement for ventilation. LEDs are self distructive in that regard and heat buildup , although not a fire hazard, can shorten the life of the luminaire as well as decreasing the light output.
 
As to fitting Batts to the existing ceiling joists, it isn't that bad a job if you use faced batting and your joists are standard width.
 
Apparently, I am not completely understanding your shop layout.

The Dow foam board you see at home building centers is extruded polystyrene (hence the XPS). Spray foam is polyurethane foam that uses an A and B component mixed together to create the foam. Yes, foam has to be sprayed onto a substrate, which can be nearly anything, including OSB, sheetrock, or even cardboard. The density of foam is usually referred in lbs, which is "lbs per cubic foot". The XPS foam is roughly 2 lbs per cubic foot, which is about the same as the closed cell spray foam. There is also open cell spray foam which is fine too, it just does not provide for a vapor barrier. Open cell foam is usually about 30% cheaper than closed cell.

Edit: As far as the LED lights go, with troffers lights installed, that should not be an issue, unless you spray foam right on top of the fixture. When I built my new house last year I built a foam box (XPS) in the attic for each can light in the ceiling and then we spray foamed the box down to the drywall along with all of the wire penetrations.
Can you tell I am a nut when it comes to insulating structures?! ;)
Oh, I also have T-studs in my house. First house in the state of Wisconsin to be built with them.
 
It really depends on you budget. Best option is spray foam to seal and insulate followed by drywall or fire resistant coating. I would do any work at the roof level and not at the drop ceiling. There are diy spray foam kits now which are easy to use. To lower cost you can use a layer of closed cell followed by open cell to build up r value
 
The T-Studs are quite a good idea. As far as foam goes, I've always thought that it would be very tough to retrofit any electrical in a foamed house.

To clarify, here is what my shop roof truss looks like. It is designed with a "room" down the center. The center 12' is decked over with OSB but the rest is open through the ceiling joists to the roof (if you ignore the drop ceiling). The actual truss has another brace in the "open" area so putting something on top of the joists for spray foam to adhere would be a piece-wise operation.

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So, why not insulate the roof trusses then? Do you have enough room for a few ceiling fans? You said you had 9 foot ceilings so that might be an option.

You are correct that retrofitting wiring after spray foam is pretty much a non-starter. But, if the foam is an issue, so would the drywall.
 
Ok. Here's what I did. My 24 x 40 workshop is in NE Ohio. Cold and long winters here. Anyways after the first season, it was obvious I needed insulation. Luckily I hadn't put in a drop ceiling yet.

I Got R38 fiberglass for the ceiling. It comes in bats (2' x 4'). So I grabbed a ladder and a staple gun and began stapling. By the time I started on the third one I was convinced this was not the way to go. I went to back to Home Depot.

I purchased 2 boxes of small 3/32" eye screws (the kind with wood screw thread). I drove them into the 24' ends of the building headers, spaced 1 foot apart, offset 6". Then I grabbed a spool of 30lb test mono-fill fishing line and strung the ceiling with it, stapling across it at every truss. This provided a scaffold of fishing line that the bats would lay on. After I completed stringing the ceiling, I had all the bats in place in less than 2 hours. Trust me it was nice to get done with the fiberglass overhead quickly.

It immediately made a difference. Then I did the side walls with R13. I did staple the tops of the R13 to keep them from falling. That was more than 20 years ago. The original plan was to put in drop ceiling, but I haven't gotten to that yet. Instead I put on temporary lighting and have been using it that way to the present. It's still on the todo list but the drywall on the sidewalls has to come first.

Addendum: With the ceiling and sidewalls insulated, I am able to heat the entire building (24w x 40L x 10h) comfortably with just two ventless ng heaters. And they cycle off even during the coldest winters.

Hope this helps or at least is food for thought.

Best Regards,
Bob
 
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2" of spray foam only has an r-value of 14. It does a good job of sealing out drafts, but if you have any kind of winter, you should be looking at R38 minimum. That's a standard 9" fiberglass batt. Mike
 
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