Shop ceiling - Victim of my own cheapness

[Eddyde]

As a General Contractor, I have a lot of experience with regular and spray foam insulation, Drywall, etc.

I don't recommend spray foaming or blown-in insulation above the drop ceiling grid. Foam will be messy and difficult to apply evenly with all the obstructions. Ceiling tiles are not designed to carry any weight and will sag even under the weigh of blown cellulose, also the troffers are not designed for insulation contact and even with LED lamps could have excess heat issues.

If you are happy with the ceiling grid an the lighting I would say leave it and insulate under the roof. There, spray foam is the quickest, easiest and best insulative way to go, but not the cheapest. Hybrid methods: Spray 2" of foam and then a layer of fiberglass batts. Or use a layer of rigid foam board or boards, depending on the desired R value, leaving a gap around the perimeter then filling the gap with spray foam sealing and securing the boards in place. I am actually using this method on a home I am currently renovating, I'll post some pictures later.

If you decide to go the spray foam route, you can either hire a contractor of do it yourself with foam kits.

 

[TCSmith]

Couldn't you just have a spray foam company spray the underside of the roof deck and seal up the soffits? My understanding is that this method doesn't require attic venting.
Minimal disturbance to the drop ceiling and shop, warm place to work. Side benefit is your storage space is warmed.

 

[7milesup]

Couldn't you just have a spray foam company spray the underside of the roof deck and seal up the soffits? My understanding is that this method doesn't require attic venting.
Minimal disturbance to the drop ceiling and shop, warm place to work. Side benefit is your storage space is warmed.

Couple of caveats with that.
1.) The thickness of the foam has to be greater than the anticipated dew point between the outside and the inside, meaning the dew point must fall within the foam thickness. If it falls inside the building envelope, you may have condensation issues. That all depends on RH inside the building. I am going to guess that considering where the OP lives, even 2 or 3 inches would meet that criteria.
2.) The method you describe TC is called a "hot roof". The one possible disadvantage is the shingle company may void the warranty. It seems that shingle companies void warranties no matter what so probably not an issue...

Edit: TCSmith... yes, I personally think that your suggestion is the most viable.

 

[Larry$]

1.) The thickness of the foam has to be greater than the anticipated dew point between the outside and the inside, meaning the dew point must fall within the foam thickness. If it falls inside the building envelope, you may have condensation issues.

So true!
That became a big problem when blown in insulation started to be used around here. With no vapor barrier moisture would enter the insulation . When it reached the dew point it would condense. The insulation would then be heavy and settle. The water would trickle down to the 2x4 plate and rot would finish the job.

 

[Howard E.]

I did my roof with 2" reflective foam attached to the roof joists & fiberglass between that & the roof sheathing; it works *very* well but you have to get seriously religious about sealing the cracks & gaps up.

 

[7milesup]

This does not reflect directly onto this thread but here is a picture of my thermostat at noon. It is set to roll back to 62 at 8am. The house had lost one degree by noon. It was -30F this morning.
This is building science done correctly. Please dont be offended by my remarks, I just wanted to show what can be done.

 

[Dabbler]

I live in Alberta, and did quite a bit of contracting in my time, so here's my 2 cents...

We regularly get -30C here and so insulation is an important thing for us. Here's a few things I've learned over 40 years:

- Don't drywall the ceiling of your shop [unless it is required by building code]. It costs (here) a similar cost for 1/2" plywood. zinc white paint is more reflective than most ceiling tiles. plywood will support insulation better. Most garages are framed with greater tolerances than a house and getting the stuff up so it stays is a real pain. Been there. plywood can be more forgiving when there is nothing to screw to - the bridge is just another piece of plywood.

- ensure you vapour barrier is correctly taped and sealed. With just vapour barrier and ply you will notice that heat will stay in better.

- if you get any serious cold weather, spraying foam on the underside of your roof will be a disaster. I've fixed 2 houses and a garage that have fallen prey to an unscrupulous insulating contractor. Given time. moisture will collect between the watertight roof and the vapour-tight insulation, resulting in structural rot. All 3 buildings had to have their roofs restructured and replaced.

- After vapour barrier and ply, feel free to use whatever insulation you like: For garages I like to roll R12 between the trusses and follow up with R12 in styroboard or another layer of laid fibreglass. If you have a good deal on blown in, it is the fastest.

-lastly, ensure that you have good ventalation for your roof cavity. Having it draw away moisture is key to keeping your structure safe.

 

[Dabbler]

For another take on doing a ceiling for warmth, have a look at Steve Summers shop rebuild: it is cheap and very good, but isn't fireproof...

 

[Scruffy]

I would never drywall anything in a shop. In my last two buildings its metal ceiling and metal on the walls.
Scruffy Ron in Ohio

 

[nnam]

I echo some above. Ventilation and moisture barrier. A thin sheet of plastic that seals well is a great heat barrier. Try reflextix or things like that.
Mold and rot is #1 thing to watch out for. Next is maintenance, people may need access there one day.
Other than that, any thick and cheap insulation would do. Watch out for great deal on overstock, private sale if you have time.

Drywall is hard to do for ceiling. Would need the lift or friends. Sanding is a pain, but a rotary vacuum sander for drywall can help, still very hard and hurt.

It all comes down to cost after all, but don't cut corner. Moisture is the problem, then cost. Everything else is about air tight and thickness.
I hate fiberglass btw, it's itchy and cancerous. But what else are out there...

Good luck with your project.