Insulate shed walls? Slab on grade

[cadunkle]

16'x'16' shed on a slab, sill plates direct to slab on grade, no blocks to raise wood above dirt. I want this to be my dirty work area for sand blaster, parts washer, and general storage kept above freezing. The second floor had a roughly 9'x9' opening which I closed in and installed and insulated attic ladder for access. I then installed a 5k watt electric heater. I'm in the process of insulating and finishing the ceiling with OSB.

It shouldn't take much to keep it above freezing once the ceiling is insulated, and even half insulated and drafty around the perimeter it'll get to around 70* with the heater running full tilt and temps around freezing. Is it worth insulation and OSB on the walls? OSB is still fairly expensive, but my greater concern is termites or water intrusion that I wouldn't notice behind a finished wall. The lot is level. Mitigation measures if I close it in?

 

[Johnny Generic]

I'm no thermal engineer but had a good sleep last night. Maybe you could rip some PTPW about six inches wide and place those along the bottom perimeter of the shed. Bring your insulation down to the top of the PTPW **** the OSB on top of the PTPW. Also would caulk between the bottom sill plates and floor. Add a small fan to help circulate warm air. 70 DEGREES IN THE WINTER THAT WOULD BE HEAVENLY.

 

[HalfTonTom]

What is PTPW?

 

[cadunkle]

Presumably pressure treated plywood. Currently the shed has T1-11 siding, not pressure treated. Sill plate is pressure treated 2x6, with 2x4 untreated on top of the for the lower plate of the 2x4 wall.

A couple years ago I did spray Bora Care on the bottom 2' of the inside (sill plate, studs, interior of T1-11). I have enough to do another treatment. I spray ground clear around the perimeter every year and keep vegetation trimmed away from the siding.

I suppose I could insulate and OSB the top 4' or even 6' of the walls and leave the bottom open for inspection and any moisture to dry quickly. The ceiling being finished will make it easy enough to heat, anything on the walls can only help. The electric heater costs about $0.80/hr to run continuously. Once it hit 70* I turned the thermostat down so it would cycle and maintain high 60s. but anything to reduce cycle time will probably pay for itself. I just don't want to create a bigger problem long term.

 

[duneslider]

You need to account for air sealing also. If you can keep that warm air in and cold out it will maintain temp longer. Gaps at doors and along floors, etc are letting cold or hot air in/out. Lots of caulk, door seals, in addition to insulation will really help.

 

[nadogail]

Blown in cellulose treated with Boric Acid is fairly effective and pretty easy on the pocket book.

 

[67CarGuy]

Blown in cellulose treated with Boric Acid is fairly effective and pretty easy on the pocket book.

Blown in cellulose on its own isn't an air barrier. @duneslider is right on - air seal before adding any more insulation. Start at the floor and work up with caulking and/or expanding foam. Mineral wool batt insulation would work for your walls, it doesn't care if it gets wet.

 

[Yankeefarmer]

16'x'16' shed on a slab, sill plates direct to slab on grade, no blocks to raise wood above dirt. I want this to be my dirty work area for sand blaster, parts washer, and general storage kept above freezing. The second floor had a roughly 9'x9' opening which I closed in and installed and insulated attic ladder for access. I then installed a 5k watt electric heater. I'm in the process of insulating and finishing the ceiling with OSB.

It shouldn't take much to keep it above freezing once the ceiling is insulated, and even half insulated and drafty around the perimeter it'll get to around 70* with the heater running full tilt and temps around freezing. Is it worth insulation and OSB on the walls? OSB is still fairly expensive, but my greater concern is termites or water intrusion that I wouldn't notice behind a finished wall. The lot is level. Mitigation measures if I close it in?

If your goal is to keep it above 24/7 during the winter months using an electric heater, you definitely want to insulate it as much as you can. Electric resistance heat is the most expensive way to heat, and there’s only one way electric rates are headed, and it’s not down!