Ceiling Insulation Options for a 24'x24' Free Standing Workshop?

[dimwittedmoose51]

Lots of Insulation Posts this time of year, but none of the previous ones I've read really answered my questions, so please bear with me.

I have a 24'/24' detached shop with steel siding and only one small window. Garage door is a 17'x7 and has the foam core construction. I'm currently installing R-15 in the 8' walls where only thin styrofoam was partially glued in and pegboard used for paneling. To say it got drafty in the wintertime would be a massive understatemen . Two winters ago I quit using my wood stove and converted to a 7500 BTU 220V AC electric unit with the understanding that I would get the shop properly insulated as I will be spending a lot of time in there all year now that I'm fully retired. We're in NE Iowa where it does get cold and windy for a good share of the winter and my lone remaining question is what to do for the ceiling. The PO had a mix of R-11, R-13, and a bit of R-19 stapled in the rafters with no sheathing to cover it up. I've chosen the white Melamine paneling for the vertical walls and have no desire to hang sheetrock up in the rafters. Since R-21 is all I can stuff into the 2x6' roof joists, would simply hanging the Melamine paneling under the current insulation be okay, or should I remove the hodge podge existing insulation and hang the Melamine followed by blowing in the cellulose or whatever fluff the big box stores sell. Also, would the extra investment in doing the latter option would be worth it, as I doubt I could blow much loose fill in those cavities after I put the Melamine up under the existing stuff.

I'd appreciate opinions greatly!! Can't afford the pros to come in and foam the rafters.

TIA,
DM&FS

 

[eegger]

Picture would be helpful, do you have storage access in the attic or do you want it closed off ?

I am currently finishing off my build and I'm doing steel panels for the ceiling and then blown-in R50 fiberglass for the rafters. I didn't want to finish drywall on the ceiling and once the steel is up, the ceiling is done. I am not using storage in the ceiling though, just an access panel if needed.

I would redo most of it and start over, Put up a plastic barrier on the ceiling, seal any cracks, outlets etc, with some can foam/tape, put up what I wanted for a ceiling and then maybe take out most of the insulation, maybe leave the R19 (depending on how it was installed and condition) and do blown in insulation. Doing it right would be worth the extra investment. Drafts would be gone and R value greatly improved.

 

[strutaeng]

I've got a same size detached garage. I've got partial 2x6 rafters insulated, but the other half has an attic that I want to open up. My roof needs replacement and the best to do in my case is add a continuous layer of rigid insulation 2" to 3" Polyiso or XPS over my existing deck (my roof deck is the flimsy 3/8" stuff anyways), then more wood panel deck and new shingles. I did something similar to my house, except all of the insulation was on top of the deck (underside structure is exposed) and worked very well. There I did like 7 1/2 total of XPS and Polyiso, staggered the joints much the same way do in commercial roof jobs. I I had to re-roof, so the timing was right. Probably not a good idea because re-roofing is expensive.

In the meantime for my garage, I thought about completing insulating the rafters and installing XPS in whole sheets on the underside, taped to act a vapor barrier. That would minimize thermal bridging from the rafters. Are you talking about the thin sheets of melamine? Those can cover the XPS.

 

[dimwittedmoose51]

Picture would be helpful, do you have storage access in the attic or do you want it closed off ?

I am currently finishing off my build and I'm doing steel panels for the ceiling and then blown-in R50 fiberglass for the rafters. I didn't want to finish drywall on the ceiling and once the steel is up, the ceiling is done. I am not using storage in the ceiling though, just an access panel if needed.

I would redo most of it and start over, Put up a plastic barrier on the ceiling, seal any cracks, outlets etc, with some can foam/tape, put up what I wanted for a ceiling and then maybe take out most of the insulation, maybe leave the R19 (depending on how it was installed and condition) and do blown in insulation. Doing it right would be worth the extra investment. Drafts would be gone and R value greatly improved.

Thanks for the response and sorry for the mega late reply. So what size and gauge of metal sheathing are you referring to? Galvanized? and what gauge? I was gonna do the 4x8 ' Melamine white panels, but they's heavy enough and flimsy enough and crack easily to make solo installation a real pain. They're working out okay for the vertical walls though I saw some "snap in" metal stuff(that's spozed to replace drywall on a FB ad, but the nearest dealer is an hour away and I have no idea what the cost per square foot would be. I'm not opposed to doing the insulation removal and doing the job correctly. The rafters will remain open for storage with no 8' ceiling or access hole. The shop was cheaply built and simply has cross beams at 8' and no trusses like the attached garage to the house does. The ridge vent I cut in the roof peak is currently plugged with removable Ethafoam wedges, but I should probably permanently seal it and put a couple ventilator things in the roof to open up once spring and summer arrive and then close once the heater fires up come November.. I could shoot a photo or two for sure.

 

[dimwittedmoose51]

I've got a same size detached garage. I've got partial 2x6 rafters insulated, but the other half has an attic that I want to open up. My roof needs replacement and the best to do in my case is add a continuous layer of rigid insulation 2" to 3" Polyiso or XPS over my existing deck (my roof deck is the flimsy 3/8" stuff anyways), then more wood panel deck and new shingles. I did something similar to my house, except all of the insulation was on top of the deck (underside structure is exposed) and worked very well. There I did like 7 1/2 total of XPS and Polyiso, staggered the joints much the same way do in commercial roof jobs. I I had to re-roof, so the timing was right. Probably not a good idea because re-roofing is expensive.

In the meantime for my garage, I thought about completing insulating the rafters and installing XPS in whole sheets on the underside, taped to act a vapor barrier. That would minimize thermal bridging from the rafters. Are you talking about the thin sheets of melamine? Those can cover the XPS.

Yes, the Melamine is 4x8' sheetsfrom Menards and maybe 1/8" thick.....and fragile. I'm gonna finish the walls first and may tackle the roof joists this spring and summer. Any pointers on sealing off the top plates since my rafters will be open. I'll be insulating and paneling and sealing the gables as well. Thanks for the ideas.

 

[strutaeng]

Yes, the Melamine is 4x8' sheetsfrom Menards and maybe 1/8" thick.....and fragile. I'm gonna finish the walls first and may tackle the roof joists this spring and summer. Any pointers on sealing off the top plates since my rafters will be open. I'll be insulating and paneling and sealing the gables as well. Thanks for the ideas.

The top plate where it's open to the rafters sitting on it?

 

[bdbecker]

Hi neighbor! While I now live in the Des Moines, I grew up about 20 miles away from Cedar Falls. I've also got a 24x24 detached garage that I've converted into my home shop.

Concerning the insulation, I'd probably stick to batt insulation and support rods so you wouldn't have to rely on the melamine panels to support any weight. Even though it wouldn't be a lot of weight, I would hate to do all that work and end up with a sagging ceiling a few years down the line.

https://www.menards.com/main/building-materials/insulation/insulation-accessories/robinson-tech-insulation-support-wire/1611760/p-1444421524998-c-5776.htm

Some insulation is better than no insulation, especially in the ceiling. It'll pay for itself in no time if you are running an electric heater.

Also, when I sheeted my ceiling, I bought a drywall lift from Northern Tool to help with the process (currently on sale for $125). As soon as I was done with my project, I sold it for $100 the same day I listed it. Well worth every penny.

Ironton Drywall and Panel Hoist 150-Lb. Capacity, 11ft. Lift | Northern Tool

This Ironton® Drywall and Panel Hoist with a convenient design can be converted into a compact format that's easy to transport an...

www.northerntool.com

Best of luck with your project!

 

[dimwittedmoose51]

The top plate where it's open to the rafters sitting on it?

Yes, I was gonna try to fill the gaps with either the Backer rod and foam over it fro the Great stuff Co. and theng;ue down the blue 2" styro foamover the top of that to attempt to seal ALL the air coming out of there right now. I bought the caulk that's especially designed for foam board to wood. Need to clean the surfaces first. Thought about vacuum and then maybe the quick evaporating Green can brake cleaner. Not sure Simple Green would be any more effective. Leaving the rafters exposed versus finishing them with some sort of paneling would definitely be cheaper and I might put that process off til next year. any thoughts on having the rafters professionally foamed. I couldn't afford having the walls done, that's for sure. Looking forward to your advice. Thanks

 

[Dig Doug]

There are a number of different ways to secure the insulation. I would get a pro to quote it. A lot of times they can install it for just A little bit more than what you buy it for.

the pro also has different types of materials that will work better for odd ball applications. You might be able to save a few bucks if you install the rods / brackets…

Finished product