Shop Insulation

[ralitaco]

So I am considering insulating my shop. It is one of those prefab 10x20 buildings, and there is currently no insulation.


I have 2 Oil Radiator heaters (not sure if that is there official name) for heat in the winter and a small window AC unit for the summer. The heaters do a very good job but the AC not so much. I plan to install some bigger vents in the top of the gables - right now they look to be about 6x12. I may even try an exhaust fan that cuts on at a certain temp, but I am getting ahead of my budget - LOL.

I ran across a business selling some of the 2" Rigid Insulation, the yellow foam with the black paper-ish on both sides. I believe this to be polyisocyanurate or polyiso. He said it was what they put on flat roofs before covering it with vinyl.
He is only asking $8 for a 4x8 sheet and I would need 25 sheets. So that means I could insulate my shop for $200 plus my labor and misc h.

So my questions are:
1. Is this stuff safe to use inside?
2. I am planning to put the insulation at the very top between the joists just below the roof sheathing. I read a lot about needing an air gap to prevent condensation.
a. How much of a gap is needed?
b. Do I need plastic or something between the insulation and the sheathing?
3. Can I glue this to the exterior walls? I do not plan to cover the walls with sheetrock or anything (trying to keep the cost down) and I thought this would be a good way to keep it in place.


Thanks in advance for your constructive input.

 

[bowman]

interested, as i need to do similar for metal building

 

[ralitaco]

interested, as i need to do similar for metal building

He is in Surf City and says he has a bunch of it. Of course with my luck, somebody will buy it all while I decide if I want to do it.

 

[bowman]

$8 sheet is a great price for 2", that would be worth a drive over $20+/sheet

 

[Bigdog72]

Cheap isn’t always better. Some things to consider:
1. Off gassing of chemicals
2. Smell from insulation
3. Mold in cavities
4. Loss of area inside the shop. 4” doesn’t seem like a lot but every bit of space is useable.

 

[Echd]

My shed is a 20x20 building that was similarly unfinished, although it was stick built on a brick base instead of a prefab. I put up fiberglass insulation and OSB on the interior walls and it only cost me about $450 or so.

Now I know currently that is a pipe dream as OSB is absurdly expensive (seriously, why is it back over $35/sheet again?), but you could probably do fiberglass batts and drywall for a very reasonable price. I do not regret doing the fiberglass over foam board at all- the insulation value is far better. You might throw batts up in the ceiling and possibly cover them with foam board though if you don't want to drywall the ceiling.

Lost space could be made up for with cleats on the wall or similar shelving.

 

[ralitaco]

Cheap isn’t always better. Some things to consider:
1. Off gassing of chemicals
2. Smell from insulation
3. Mold in cavities
4. Loss of area inside the shop. 4” doesn’t seem like a lot but every bit of space is useable.

Geoff, I agree with your cheaper isn't always least expensive thoughts. That is why I am asking.
Are you saying that type of material off gasses and smells?
Also, why would there be mold? I guess that is why there needs to be an air gap...to the end, I am thinking I could put the 4x8 sheets perpendicular on top of the rafters instead of between them, at least on the ceiling. That would leave a 3/5" air gap.

 

[ralitaco]

My shed is a 20x20 building that was similarly unfinished, although it was stick built on a brick base instead of a prefab. I put up fiberglass insulation and OSB on the interior walls and it only cost me about $450 or so.

Now I know currently that is a pipe dream as OSB is absurdly expensive (seriously, why is it back over $35/sheet again?), but you could probably do fiberglass batts and drywall for a very reasonable price. I do not regret doing the fiberglass over foam board at all- the insulation value is far better. You might throw batts up in the ceiling and possibly cover them with foam board though if you don't want to drywall the ceiling.

Lost space could be made up for with cleats on the wall or similar shelving.

WOW!!! 20x20 for $450!!!! That had to be a while back.
Right now batt insulation looks to be about $400 for my 10x20.
Drywall would run about $300.

 

[Echd]

Unfortunately it was only a few years ago... materials have just gone insane since then.

300 for drywall for that space seems high, at least for just the materials though.

 

[DSWalker]

Search Marketplace and Craigs list regularly. People buy too much and then will sell the unused or leftover cheaper than they bought it. Ive also seen similar from contractors. You can get good deals if you are patient and not in a big hurry. I insulated my shop walls and ceilings for well under $500. It is 24 x24. R 30 &39 in ceilings and all the south and west walls are R30. R19 in the others.

I run my mini split 24/7 and the utility bill only went up about $20 to $25.

 

[Chris C]

I had my 24x36 shop walls and ceiling insulated (R-13 batt) just over a year ago... cost $1250. That included foam sealing around the foundation, windows and doors.

Best part... I didn't have to touch it.

 

[Craptastic]

Just finished doing the mud and paint on my 24X16 shop walls and figure I sunk about $280 in drywall and 45 minute mix plaster and another $425-$450 in insulation. Prices had definitely gone crazy but if I wanted to use the shop it needed to be done. I figure the ceiling is going to run about $1100 to $1200 between lumber/drywall/insulation.

Prices are coming back down, but like gas, they never get back down to where they were before.

Not sure I would use a foam or polyiso insulation in a space I (or anybody else) would be inhabiting and using power tools in. Inherently more at a fire risk than a normal home and there's some nasty stuff that off gasses or is released if there ever is a fire. Depending on the blaze you might make it out fine but end up with a lifetime of lung issues from the effort to escape.

 

[Bigdog72]

Geoff, I agree with your cheaper isn't always least expensive thoughts. That is why I am asking.
Are you saying that type of material off gasses and smells?
Also, why would there be mold? I guess that is why there needs to be an air gap...to the end, I am thinking I could put the 4x8 sheets perpendicular on top of the rafters instead of between them, at least on the ceiling. That would leave a 3/5" air gap.

Jim: I was saying that insulation and, especially the type you are considering, throw off chemical fumes. They need to be covered or segregated from the inhabited area. This can be done many ways. Most popular insulation technique for a shop would be to insulate the cavities and cover with drywall or some other sheathing material. It’s important to seal along the plates because mold needs oxygen and moisture to grow. Control both = no mold. In the ceiling mold growth is controlled by air movement. That’s why a baffle is used between rafters to help move air. It’s harder to explain than it should be. If you go to the Owens-Corning website there is plenty of how to info.

 

[Bigdog72]

Jim: I was saying that insulation and, especially the type you are considering, throw off chemical fumes. They need to be covered or segregated from the inhabited area. This can be done many ways. Most popular insulation technique for a shop would be to insulate the cavities and cover with drywall or some other sheathing material. It’s important to seal along the plates because mold needs oxygen and moisture to grow. Control both = no mold. In the ceiling mold growth is controlled by air movement. That’s why a baffle is used between rafters to help move air. It’s harder to explain than it should be. If you go to the Owens-Corning website there is plenty of how to info.

This is good place to start: Residential and Home Insulation | Owens Corning Insulation

 

[Skymaster]

Your 2" polyiso has an R value of 12.4!!!!!!! grab every sheet you can!!!!!!!!!!!!!!!!!!!

 

[Oka]

Metal building type roll insulation is usually 3' wide with plastic on it. There is a slightly more expensive version that has plastic on both sides. Either way, because of the special application , you might find some one selling left over rolls for a real discount.

interested, as i need to do similar for metal building

 

[ralitaco]

Unfortunately it was only a few years ago... materials have just gone insane since then.

300 for drywall for that space seems high, at least for just the materials though.

If my math is correct, I'd need:
5 sheets for each 20' wall = 10 sheets
2.5 for the 10' end walls = 5 sheets
10 sheets for the ceiling -
That would make the grand total 25 sheets of drywall @ $12/sheet = $300 plus I would still need baffles for the ceiling.
Material costs are crazy right now. They are better than when I bought the shop which is why I didn't insulate it then.

 

[ralitaco]

Search Marketplace and Craigs list regularly. People buy too much and then will sell the unused or leftover cheaper than they bought it. Ive also seen similar from contractors. You can get good deals if you are patient and not in a big hurry. I insulated my shop walls and ceilings for well under $500. It is 24 x24. R 30 &39 in ceilings and all the south and west walls are R30. R19 in the others.

I run my mini split 24/7 and the utility bill only went up about $20 to $25.

That is a good idea. I am not in any hurry.

 

[ralitaco]

Just finished doing the mud and paint on my 24X16 shop walls and figure I sunk about $280 in drywall and 45 minute mix plaster and another $425-$450 in insulation. Prices had definitely gone crazy but if I wanted to use the shop it needed to be done. I figure the ceiling is going to run about $1100 to $1200 between lumber/drywall/insulation.

Prices are coming back down, but like gas, they never get back down to where they were before.

Not sure I would use a foam or polyiso insulation in a space I (or anybody else) would be inhabiting and using power tools in. Inherently more at a fire risk than a normal home and there's some nasty stuff that off gasses or is released if there ever is a fire. Depending on the blaze you might make it out fine but end up with a lifetime of lung issues from the effort to escape.

Thank you Matt. That is what I was trying to understand about that poly stuff. Also as I was reading, it occurred to me that the black paper would make the shop very dark. I am now thinking about regular faced insulation in the ceiling and covering it with a layer of EPS with the reflective face that will help bounce light. Or just some with a white finish. The more I type this, the more I like that idea for the ceiling so I don't have to manhandle drywall up in the rafters.

 

[ralitaco]

Jim: I was saying that insulation and, especially the type you are considering, throw off chemical fumes. They need to be covered or segregated from the inhabited area. This can be done many ways. Most popular insulation technique for a shop would be to insulate the cavities and cover with drywall or some other sheathing material. It’s important to seal along the plates because mold needs oxygen and moisture to grow. Control both = no mold. In the ceiling mold growth is controlled by air movement. That’s why a baffle is used between rafters to help move air. It’s harder to explain than it should be. If you go to the Owens-Corning website there is plenty of how to info.

Thank you Geoff for that explanation. So it will be a NO from me on the polyio stuff.
And thanks for the link. I will be reading that later.