Insulating small 14x24 shop

[slomaro3.4]

Hi all I've finally got electric going in next week and a 12k btu mitsubishi mini split a couple of weeks later in my 14x24. I've let scope creep get away from me a bit, initially it was built with a ridge vent and I was going to use baffles and batts to insulate some, but with the mini split I think I can make this a comfortable year round space. The walls will still be getting R15 rockwool and OSB I'm just in analysis paralysis on the ceiling. I'm located in climate zone 6b.

Goal: Year round useable shop in climate zone 6b without running the daylights out of my mini split
Options I'm weighing:

• Spray foam the ceiling, seal up the vents and do a hot roof (most expensive), might be able to get in the low R20s
• Baffles and batts for R15
• Baffles and batts + 2 inch foam board underneath aiming for the low R20s (I think this starts to cost as much as spray)

I don't have a huge desire to finish the ceiling post insulation, but maybe that could add something? I could add in some 2x6s and blow in insulation, but I'm not sure I want to lose the headroom if I don't have to and I like my 4ft deep storage loft in the back. Can someone school me on what they think the best plan of attack would be?

 

[readhead]

Having been a shed dealer I am surprised that the builder used radiant barrier siding but didn’t use it on the roof where it would be the most effective. That doesn’t matter now.

You should be able to heat a 14x24 with a match once it is insulated. R15 in the walls will work fine. I would fur the trusses 2” so you can use R21 in the roof.

Is the floor wood? If so caulk the joint at the bottom plate and seal the floor.

 

[slomaro3.4]

Having been a shed dealer I am surprised that the builder used radiant barrier siding but didn’t use it on the roof where it would be the most effective. That doesn’t matter now.

You should be able to heat a 14x24 with a match once it is insulated. R15 in the walls will work fine. I would fur the trusses 2” so you can use R21 in the roof.

Is the floor wood? If so caulk the joint at the bottom plate and seal the floor.

Yeah not sure on the radiant barrier, to be honest I moved quickly on the structure because the price was about 1/2 what I was expecting. Seems solid so far. The floor is a 5" concrete pad and the walls have a thin foam strip beneath them, but I should probably think about making sure they're sealed too. I hadn't even thought to fur the trusses which seems like it'd be a good middle ground.

 

[racecougar]

Are the soffits vented? You mention ridge venting but not the soffits.

 

[slomaro3.4]

Are the soffits vented? You mention ridge venting but not the soffits.

They are not, if I do baffles I'll need to vent the soffits. I definitely should have thought through ceiling insulation more when building.

 

[readhead]

I would not worry about venting the roof.

 

[slomaro3.4]

I would not worry about venting the roof.

only in the case of spray foam or for batt insulation as well?

 

[dcg9381]

Just for the pain in the *** factor and to keep the roof height, I'd spray that roof deck and then do foam/board and/or traditional bat on the rest of it. 6b is pretty cold though...

This space is small enough that a DIY kit (tigerfoam etc) might make sense over a contractors.

I'm on my 3rd space with foam insulation, no failures, love the stuff.. Buy YMMV. Enclosed spaces up north that are tightly sealed of have ERV/HRVs for moisture control, not something we have to deal with in the south typically.

 

[readhead]

only in the case of spray foam or for batt insulation as well?

I have seen to many spray foam failures in my time to recommend it. (Begin haters here). Install batt insulation and then a vapor barrier and then the final finish. Enjoy your new space. Hopefully there was a vapor barrier installed under the concrete. If not then a tuff sealer should be applied to reduce the possibility of condensation.

 

[slomaro3.4]

Just for the pain in the *** factor and to keep the roof height, I'd spray that roof deck and then do foam/board and/or traditional bat on the rest of it. 6b is pretty cold though...

yeah SW Pennsylvania so we get some fun temperature swings. I agree on the PITA factor, I don't have a huge desire to be dealing with fiberglass over my head on an 8ft ladder. traditional batt in the walls is the route I'm going for sure.

I have seen to many spray foam failures in my time to recommend it. (Begin haters here). Install batt insulation and then a vapor barrier and then the final finish. Enjoy your new space. Hopefully there was a vapor barrier installed under the concrete. If not then a tuff sealer should be applied to reduce the possibility of condensation.

There is a vapor barrier under the slab, in the end I'm kicking myself that I should have insulated under it as well, but it is what it is. Were there any red flags prior to the spray foam failures?

 

[readhead]

The spray foam failures I have seen are mostly from poor installation and improper material mixing. Material coming loose because of poor adhesion and trapping moisture between the foam and the substrate. I have some involvement in loan payment inspections and spray foam is showing up as a red flag in remodels. I have a feeling that spray foam may be the next synthetic stucco mess.

 

[slomaro3.4]

The spray foam failures I have seen are mostly from poor installation and improper material mixing. Material coming loose because of poor adhesion and trapping moisture between the foam and the substrate. I have some involvement in loan payment inspections and spray foam is showing up as a red flag in remodels. I have a feeling that spray foam may be the next synthetic stucco mess.

makes sense, I'm planning to pay someone to do the ceiling either way. But I'm now sitting here looking at a couple of spray foam quotes that are both around $5/sqft for 3 inches at a claimed R21 vs $3/sqft for batts and baffles and I have to figure out my gables. Closed Cell is basically a $900 premium over the batts if I include some foam board for the gables.

I like that the spray foam includes my gables, I dislike your mentioned concerns, but the spray foam quote I'm leaning towards includes a lifetime warranty from a company that has been around for 20ish years.

 

[dcg9381]

The spray foam failures I have seen are mostly from poor installation and improper material mixing. Material coming loose because of poor adhesion and trapping moisture between the foam and the substrate. I have some involvement in loan payment inspections and spray foam is showing up as a red flag in remodels. I have a feeling that spray foam may be the next synthetic stucco mess.

They're having some trouble with it in Europe, but I suspect most of those applications are on some very old structures that were not never designed for that insulation type.. Or need ERV/HRV.

Bad thing about spay foam is that it's going to hide everything, you can't exactly peel it back and see what's under it, so I get why it'd be an inspection concern.

We've been using it for more than 10 years, no failures... Like any insulation it's going to "work poorly" if it's not adhered property, not mixed property, installed by someone with poor "spray skills"..... OR if you end up with tightly sealed envelope and have a lot of moisture that you're not controlling by HRV/ERV.

makes sense, I'm planning to pay someone to do the ceiling either way. But I'm now sitting here looking at a couple of spray foam quotes that are both around $5/sqft for 3 inches at a claimed R21 vs $3/sqft for batts and baffles and I have to figure out my gables. Closed Cell is basically a $900 premium over the batts if I include some foam board for the gables.

It's basically a price swing of 200-300% here for "new construction" on traditional vs spray foam. The R value only tells part of the story.
I've only used open cell. No objection to closed cell, but open cell is usually less expensive per R-value. The difference is how much space it requires.

 

[slomaro3.4]

They're having some trouble with it in Europe, but I suspect most of those applications are on some very old structures that were not never designed for that insulation type.. Or need ERV/HRV.

Bad thing about spay foam is that it's going to hide everything, you can't exactly peel it back and see what's under it, so I get why it'd be an inspection concern.

We've been using it for more than 10 years, no failures... Like any insulation it's going to "work poorly" if it's not adhered property, not mixed property, installed by someone with poor "spray skills"..... OR if you end up with tightly sealed envelope and have a lot of moisture that you're not controlling by HRV/ERV.


It's basically a price swing of 200-300% here for "new construction" on traditional vs spray foam. The R value only tells part of the story.
I've only used open cell. No objection to closed cell, but open cell is usually less expensive per R-value. The difference is how much space it requires.

Yeah that's valid, I'm planning on being in this house for a long long time so hopefully an inspection is never an issue, but who knows. Hopefully less of a concern from buyers since it's a detached structure. My roof is framed with 2x4s so the closed cell requiring less space is a nice perk.

I'm still leaning that way, so I guess we'll see how it goes. Might try and talk down the price a little bit more.

 

[dcg9381]

I'm still leaning that way, so I guess we'll see how it goes. Might try and talk down the price a little bit more.

Have you looked at Tigerfoam? Generally the DIY "kits" are more expensive than having a contractor do it, but I'm sure that the price difference scales down if you're not using a lot of material and have a small project.

Cover the floor. It will get on the floor and it's hard to clean up.

 

[slomaro3.4]

Have you looked at Tigerfoam? Generally the DIY "kits" are more expensive than having a contractor do it, but I'm sure that the price difference scales down if you're not using a lot of material and have a small project.

Cover the floor. It will get on the floor and it's hard to clean up.

Just priced it out and I think I'd get stuck with 3 kits to get 3" depth which would make DiY about $450 cheaper. I do think my project is small enough that I'm getting gouged some for them to just show up.

 

[dscheidt]

Just priced it out and I think I'd get stuck with 3 kits to get 3" depth which would make DiY about $450 cheaper. I do think my project is small enough that I'm getting gouged some for them to just show up.

have you checked the price including the walls? Waiting till spring?

 

[slomaro3.4]

have you checked the price including the walls? Waiting till spring?

Yeah I’m just tossing rockwool into the walls. The installer said they can spray in Feb and they’ll still warranty their work so I think I’ll let them take a swing at it.

 

[slomaro3.4]

Does anyone have any pro-tips for air sealing the 2 2x4s that are where the wall sections join together? I'm thinking either a polyurethane caulk or low expansion foam, but it's going to go behind OSB so I just want to make sure.

 

[mike93lx]

Does anyone have any pro-tips for air sealing the 2 2x4s that are where the wall sections join together? I'm thinking either a polyurethane caulk or low expansion foam, but it's going to go behind OSB so I just want to make sure.

You have a large enough gap that you can get a foam can tip in there? I hope not.

Is the exterior siding done? If not, I'd tape the seam on the outside. On the inside, caulking would be my choice

 

[Jackfre]

“Getting gouged” Have to say that for that job getting gouged and having someone else do it would put a smile on my face and a song in my heart. This assuming the y know what they are doing. There are some jobs you just want someone else to do.

 

[slomaro3.4]

You have a large enough gap that you can get a foam can tip in there? I hope not.

Is the exterior siding done? If not, I'd tape the seam on the outside. On the inside, caulking would be my choice

Siding is already on so I figured caulking thank you!

“Getting gouged” Have to say that for that job getting gouged and having someone else do it would put a smile on my face and a song in my heart. This assuming the y know what they are doing. There are some jobs you just want someone else to do.

Ain't that the truth! End of the day I got 3 quotes for foam in the ceiling and they were all in the same range so I'm just going with the good reviews and the guy I liked.

 

[slomaro3.4]

Any thoughts on sealing these gaps before spray foam? I was thinking either caulk or low expansion foam.