"Clean" shop inside of my barn. Design advice?

jcwells · Jan 31, 2021

Hey, all...

I've got a 40' x 60' steel barn with a nice concrete floor. Full building is spray foamed on the inside, nice and tight. I'm fixin' to build out a 20' x 40' x 9' tall section to be used as a "clean" shop and crafting space for my wife and I. The "ceiling" of the space has already been built as a loft/storage area, accessed by a staircase outside of the 20'x40' footprint. Floor has already been beautifully epoxy sealed. The intent is to condition this space with a mini-split system, while the remainder of the barn is unconditioned.

My first dilemma is how to construct and insulate the walls of the 20'x40' space, and how to insulate the "ceiling". Spray foaming is an option, but expensive and perhaps overkill. If I go fiberglass batts, does the vapor barrier need to face the conditioned space, or the unconditioned space? Would R-11 fiberglass be sufficient (2x4 stud walls), or do I need to go to R-19 (2x6 stud walls). I'm located in North Texas, hot and humid in the summer, cool and sometimes humid in the winter.

I'll certainly have more questions as I go along, but this is a pretty fundamental one that I need to resolve before I shoot the first wall down.

Thanks!

John

nybirdman · Jan 31, 2021

I would go 2x6 walls and insulation and finish both sides.I friend just built a new shop and used white painted metal on the interior walls and ceiling: it looks great and really lights it up.With the price of OSB/paint, it made a lot of sense.

user.69169 · Jan 31, 2021

First thing I think is you too far down plannin road widout lookin at biggest problem wid 'clean room'. You got storage dust generator gonna become ceiling. I get some kind of barrier on bottom of dat first. Barrier alone provide insulation value.

Gotta remember insulation only RETARDS heat den it saturates and conducts heat.

Second you insulating against heat, mainly re-radiated heat more den cold. Already got roof and deck working for you. Dat gives you opportunity to slow down solar gain quite a bit. Maybe think some on walling deck, even if just curtain and use vent fan to let nature cool storage & 'clean room' at night if you got enough temp difference at night. You got water? Wet roof sheds lot of solar gain during day. Refrigeration by evaporation at roof no different den how it works in evap coil. Ford Motors loves wet roofs, saves ton of money too.

Walls not so big thing, use de girts to provide support and use silver mylar to reflect heat back to wall. Gives you about 8" dead air space at low cost. Inside walls, ceiling already supported so steel studs and drywall on one side all you need.

Whole lot of things can be done cheaper den air conditioner running even if AC unit free.

jcwells · Jan 31, 2021

(removed) said:
First thing I think is you too far down plannin road widout lookin at biggest problem wid 'clean room'. You got storage dust generator gonna become ceiling. I get some kind of barrier on bottom of dat first. Barrier alone provide insulation value.

Gotta remember insulation only RETARDS heat den it saturates and conducts heat.

Second you insulating against heat, mainly re-radiated heat more den cold. Already got roof and deck working for you. Dat gives you opportunity to slow down solar gain quite a bit. Maybe think some on walling deck, even if just curtain and use vent fan to let nature cool storage & 'clean room' at night if you got enough temp difference at night. You got water? Wet roof sheds lot of solar gain during day. Refrigeration by evaporation at roof no different den how it works in evap coil. Ford Motors loves wet roofs, saves ton of money too.

Walls not so big thing, use de girts to provide support and use silver mylar to reflect heat back to wall. Gives you about 8" dead air space at low cost. Inside walls, ceiling already supported so steel studs and drywall on one side all you need.

Whole lot of things can be done cheaper den air conditioner running even if AC unit free.

Got some good points there, (removed). Figure that I've got the "dust generator" part covered by going with a finished, sheet rock ceiling in the room. Insulation batts in the ceiling, between the joists that make up upper floor storage. Again, could go spray foam instead, but a lot more expensive. If using batts, which side should the vapor barrier point to, conditioned side or non-conditioned side?

user.69169 · Jan 31, 2021

jcwells said:
Got some good points there, (removed). Figure that I've got the "dust generator" part covered by going with a finished, sheet rock ceiling in the room. Insulation batts in the ceiling, between the joists that make up upper floor storage. Again, could go spray foam instead, but a lot more expensive. If using batts, which side should the vapor barrier point to, conditioned side or non-conditioned side?

No desire to screw up yer plan, BUT how much all dat drywall gonna weigh? You in Texas, don't see insulating bottom of deck as enough saving to justify cost. Vapor barrier goes on living side de envelope. Idea is to be sort of check valve letting moisture out and not in. Honestly don't see need for vapor barrier on bottom of deck. Was my place I be looking for store getting remodeled to get grid and tile from free. (removed) is CHEAP!
Keep in mind, insulation only retards. How you gonna shed built up heat in insulation during night?

You need more to spend few bucks on infrared thermometer or better on infrared camera. Den you dealing wid real numbers. Do little experimenting and refine thunk of problems to reality.

Couple years back played wid buddy's van his dog rode in back of. Dog livin large, got second battery to vent fan in sidewall, computer fan worked good. Shot pics of roof thermals, 115 on inside wid fan running. Spray bottle proved roof dropped to 85 from evap cooling. Adding foam not worth money, Mylar mirror film bounced infrared back to roof did better by degree or 2. Put microspray nozzles and windshield pump in along wid 5 gallon water bottle. Thermostat in dog area turned pump on or off, cycle timer acted like expansion valve.

Dog was real wisewoof. Sit in van and wait for hot lookin babe to get close and den start cryin to her how he suffering. Babes call 911. Dog sitting in cool van laughing at babe sweating makeup off waiting for cop. Got to the point 911 make babe give dem plate number so dey can tell babe dog lies. Cops generally rolled by to watch irate women yelling at buddy. K-9 cops really loved it.

Popgadget · Jan 31, 2021

I would stick with spray foam. If I understand you, the entire 40 x 60 is already foamed, so if your clean shop isn't in the middle of the building it will already have 3 foamed walls, leaving you with one more and the ceiling. being closed cell, the foam make a great vapor barrier, and of course its not penetrated by dust. finishing the inside walls with metal might not be a bad idea depending on what you want to do with lighting and utilities. The profile of the siding may create headaches for mounting things on it, and for outlet boxes, switches and lights. there are workarounds for all of those if need be.

user.69169 · Feb 1, 2021

Nother thing bout drywall ceiling, drywall itself gonna weigh 1280 pounds. Dat take away from deck capacity half a ton you not able to store upstairs.

jcwells · Feb 1, 2021

Prime directives from my wife are:

The room must be cool in the summer and warm in the winter. Temperatures controlled in the mid-60's to mid-70's when she's working.
The room will be nicely finished, with paint and good lighting. No "tin barn shop" finish in her space!

Epoxy floor was considered to be a "compromise". Basically has to be finished to an "inside the house" level. My concerns are mostly centered on avoiding any potential condensation problems because the rest of the shop is not conditioned space.

Here are some photos to better show what I've got.