# Insulation recommendation for small shop



## J S Machine (Oct 6, 2009)

I have a shop I am working on that will house some expensive cnc machines and other metal working machines. I have it just about dried in. It is typical wood frame insulation and sheathed with 7/16 OSB. I added to this garage type structure to enclose it. The previous builders put in actual plywood as roof decking and it has a shingle roof. The frame is totally exposed inside - no ceiling or wall coverings. When finished, it will have the gap area going over the top caps of the wall framing into the soffit boxes. The soffits will be enclosed and vented, but still that is a place for air to get in or out. I don't know if I should add a ridge vent or not. The building will be vinyl sided when complete.The building will likely never have a ceiling or wall coverings on the inside.

Here are some pictures



















About 80% of the building's front is the thin metal roll up door. It has no insulation. When I asked the door supplier about that, they said it raises the cost significantly and it isn't that great so I opted to go without it. I got it in white to reflect heat as much as possible. 

I am in central AL where the humidity is usually about 150% and the temps hit 100 degrees F. It really is miserable here in the dead of summer. Winter is bearable ion an enclosed building out of the wind, but I would like to insulate to keep the warmer air inside.

I am ok with working in the shop with the rolling door open and a box fan blowing in fresh air, but I will most likely install a small window unit air conditioner in the small 3x2 window. I know it won't do much, but it will at least cool a little. This shop will likely never be central heated and cooled. 

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I need recommendations on what to do as far as insulation. I don't want to spend a lot of money on it if it isn't going to do much. I'm looking for as little cost as possible. I did not factor in the cost to insulate this building in the original remodel plans, and I am paying out of pocket for this. I mean if it isn't going to do much good anyway, I can go buy some of the cheaper 3/4 - 1" styrofoam or closed cell foam 4 x 8 sheets and just cut it to fit. I would like to do it myself, and avoid the labor cost of the spray in job (from my neighbor - see next paragraph) to save a little money if it is feasible. 

I have a neighbor that my family is good friends with that does spray foam insulation. He would probably give me a pretty good deal, but I don't know if it is feasible to do it. I have no idea about costs.

I was hoping someone here could give me some ball park figures as far as installation costs. There is roughly 650 sq feet on the walls and underside of the roof. This is what would have to be sprayed. Again, I don't know what type would be good or how thick. If a ridge vent needs to be added I can do that. 

I understand that spray foam is very efficient and I would likely spend a little money to get it done, provided the benefit will actually be there.


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## Ron6519 (Mar 28, 2007)

Depending on your budget you can go fiberglass batts or foam. Considering the garage door is not insulated, I don't think foam makes sense as one side of the building is not insulated.
I would add vents on the roof and soffit vents along the side to get the superheated air out of the building.


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## Windows on Wash (Aug 30, 2011)

Moisture is your enemy here. 

You will be making some humidity indoors as well as having a bunch outdoors (Alabama).

I would look a some rigid foam exterior prior to the siding and if you are going to be working in the winter, make the roof a hot roof and insulate it. 

Ideally, some rigid foam on top of the sheathing would be great but you will need to peal the roof to do it.


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## J S Machine (Oct 6, 2009)

The more I read on spray foam the more I don't like it. I'm sure it is expensive, but the bad install jobs and possible off gassing of bad chemicals seems like something that I don't care to take a chance with. 

I can do a ridge vent. I did one on another very similar building I built and it made a huge difference. If the shop was closed, walking into it on a hot summer day wasn't bad..it was actually cooler. I suspected the air flow was coming into the soffit vents and helping draft up along the underside of the roof decking and out of the ridge vent.

Any idea what batting insulation ballpark cost would be?


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## J S Machine (Oct 6, 2009)

The building will need a new roof soon, but I didn't have enough in the project budget to do it. So you all are suggesting actually insulating the outside of the building before installing vinyl siding?


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## Ron6519 (Mar 28, 2007)

"Any idea what batting insulation ballpark cost would be? "

Just measure the building and go to the local supplier to see what they charge. Or go online and check the big box stores if they are local.


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## Windows on Wash (Aug 30, 2011)

J S Machine said:


> The building will need a new roof soon, but I didn't have enough in the project budget to do it. So you all are suggesting actually insulating the outside of the building before installing vinyl siding?


When is the roof going to be ready for replacement?

It's always you replace it in insulated prior to the wintertime temperature setting in, you should be fine.

You can go ahead and insulate the space between the rafters now prior to drywalling the ceiling. Be sure to block off the soffit insulate that exterior top plate area.


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## J S Machine (Oct 6, 2009)

I stated in my original post, there will be no drywall going in this. The inside framing and ceiling joists will be left exposed. I have no intention of adding a ceiling or wall coverings. I'd like to, but I don't have the money to do it. 

That's why I'm trying to figure out what insulation would be best, or if it is even feasible. Since the attic space is left open, and there is a place for air to come in and out above that top cap to the soffit vents, and there could be a ridge vent (if I add one) for air to get out there, the walls and underside of roof may just be a waste of money.

roof will be later on down the road. Probably 2-3 years. It will cost another $700 or so if I do it myself, and I don't have that right now.


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## Windows on Wash (Aug 30, 2011)

Didn't read if very carefully on the phone. 

If there isn't going to be any interior covering (recommended for at least the ceiling), you are definitely going to want foam to the exterior. The framing members will get cold as part of the thermal conduction and if you have high interior humidity (likely if the CNC machines use a coolant/lubricant cutting fluid), you are going to have condensation on both the framing and the backside of the sheathing. 

Any fibrous insulation in this case is not going to stop air or vapor movement. 

Spray foam would be the best if you want to leave it open but it will cost you and will require an intumescent barrier to be code compliant.


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## J S Machine (Oct 6, 2009)

Windows on Wash said:


> Didn't read if very carefully on the phone.
> 
> If there isn't going to be any interior covering (recommended for at least the ceiling), you are definitely going to want foam to the exterior. The framing members will get cold as part of the thermal conduction and if you have high interior humidity (likely if the CNC machines use a coolant/lubricant cutting fluid), you are going to have condensation on both the framing and the backside of the sheathing.
> 
> ...



Ok, so if I go foam on exterior, how thick and what type, and will it hurt to put it over the felt that is already up? 

Also, I assume I can still put vinyl siding on over it, I'd just have to use longer nails to compensate for the thickness of the insulation sheet?


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## Gary in WA (Mar 11, 2009)

I'd use RB on the walls/ceiling, leaving 3" gaps at bottom/top of walls and center run of ceiling to vent it as you don't want cavity insulation covered, or ceiling drywall or heating/cooling.

Gary


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## Windows on Wash (Aug 30, 2011)

Depending on how much you cool it, any sort of class 1 vapor retarder on the cool side could be problematic.

Are you running cutting fluid on these?


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## Gary in WA (Mar 11, 2009)

Portable AC without the wall/ceiling covered won't do much farther than few feet away from unit. No covering on walls means radiant heat on solar side will heat the whole building. Adding FG (air-permeable) won't help much as not air-tight; only condensing on the fibers in cavity. Cavity insulation in winter helps a little, but very little in summer. Cavity insulation requires a cover to be effective and safe, unless you like fiberglass fiber itch... 

Radiant barrier (tin foil) on the walls in summer; encourages colder (denser) air in to garage to vent up each wall cavity (stack effect) continuously like little chimneys and venting warmer air to ceiling/ridge vent. Any warmer air (from people/machines) will rise up and out the ceiling through the gap. 
RB in winter; reflects 95% of heat from space heater unit/machine motor heat back into garage, partially close the 3" wide X length of garage ceiling vent to capture some heat yet allow moisture from people/machines to attic space/vent out ridge.

RB in summer; stops most of radiant heat through walls/ceiling with non-reflective foil and promotes cooling by convection. RB in winter is not as effective R-value as FG (which requires cover on walls/ceiling +$$$) but if OSB is air-tight or housewrap, the bottom of wall gap could be simply be covered for a dead-air-space for better R-value.

Price out FG with cover, compared to radiant alone, quite a difference. SPF and foamboard are too much money; "The building will likely never have a ceiling or wall coverings on the inside."------- "This shop will likely never be central heated and cooled. "--------------"I don't want to spend a lot of money on it if it isn't going to do much. I'm looking for as little cost as possible.".

Gary


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## Windows on Wash (Aug 30, 2011)

Good information and agreed. That is why I put the "depending on how much you cool it" part. 

The interior space there won't be reflective of normal living spaces. If he is running cutting fluid, there is going to be a bunch more humidity in the space as well as other non-standard conditions.


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## Gary in WA (Mar 11, 2009)

I agree. Money is the issue, I think. Been there, done that. Haven't we all...

Gary
PS. WoW; http://www.diychatroom.com/f9/lp-smart-siding-tyvek-wrapped-frame-299842/


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## Babaloosanchez (Apr 27, 2012)

I have a metal building and i just want to heat it in the wintertime. I live in Alabama so it doesn't get real cold. It is metal, on purlins, on 2x4 frame. Can I put batts between the studs since i am only heating in the winter? It has no vapor barrier. What would be the best route to take? I can't do spray foam insulation. it is only a 12x16 shed. Thanks in advance.


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