I am getting ready to build a 40x80 pole barn/shed. It will have the standard vinyl faced insulation that they put up while they are installing the metal skin. However on one end of the building i am wanting to wall off a 30 foot section to make a heated/cooled work shop. So i am wanting to find some ideas or information on the best way to do this that will have a high R value. The whole shed will have a cement floor in it but for the 30 foot end i plan to use as my work shop i plan to make it a 6 inch insulated floor for some thermal mass. My question is mostly related to the walls and or ceiling/roof. Any input would be greatly appreciated. Thanks

P.S. this is the company i plan to go with since they are local to me. http://www.qualitystructures.com/construction_process.html

I would suggest approximately three inches of closed cell spray foam on the walls depending on your climate zone. If you are putting a ceiling in, then I would blow R40 to R50 cellulose on the attic floor. If you go with the spray foam on the walls it will have to be covered with a suitable thermal barrier.

I agree with insulateright about using spray foam, though I'm not sure why you'd need to cover it with a "suitable thermal barrier." Did you mean moisture barrier?

Anyway, the biggest reason to go with spray foam in the walls over fiberglass or cellulose is its ability to create an air seal. You would not believe the difference between regular studded walls with fiberglass and a sprayed wall, or SIP. This is a layer of protection and retention that can't be conveyed by R-value alone. SIP sales people will tell you their buildings operate at 2x the R-value of standard construction... what they really mean is that because you've stopped wind and moisture from entering, or conditioned air from exiting your building envelope, the two buildings, though similar in R-value, will have drastically different performance.

Think of it this way... put on a sweatshirt (stud/fiberglass construction) or a lined windbreaker (spray foam or SIP) and you'll probably feel just as warm in either one... inside. Step out into a blustery fall or winter day, and you'll notice a HUGE difference.

I'm struggling with a similar design question... I want to build a SIP barn, but the price difference adds up quickly. When you aren't using a space every day, like a shop, it's hard to plunk down the equivalent of 20+ years of utility bills to get a more efficient shop.

I wish you well, and hope to hear more input on this topic!

But you can build a studded wall to be as air tight as any other construction method - just need to get all the detailing right.

For the inside framed walls that will be against the exterior walls, frame them with 2x4 while laying flat on the concrete, then attach 1/2" or thicker foil faced polyiso insulation to the studs. Tape or caulk seams to form air barrier. Stand up walls, brace, and secure to floor with anchor bolts or tapcons. Now do essentially the same for the wall facing open spaces, but you can put the outer foam sheathing on after the walls are up. Again, tape or caulk seams to block airflow. Caulk bottom plate to concrete floor to air seal as well. For the ceiling I would use engineered I joists suitable for the span and loads you will have. Will you be using the ceiling over this area for storage? If so, factor that in to your joist spans (most span tables for these I joists assume a 10 lb/sq ft dead load (stuff permanently attached to the joists like sheetrock, flooring, insulation, etc.) and 40 lb/sq ft live load (stuff not attached to the floor like people, furniture, boxes of stuff, etc.). A 30' span will most likely require a mid span support beam unless you go with really deep I joists. If you split the span in half, you can easily go with the smaller (and less expensive) 9-1/2" I joists @ 16" on center. The mid span beam could be level with the top/bottom of the joists if you use shorter I joists (also easier to handle) and set them in metal joist hangers attached to the beam. You would likely need one or two posts to support this beam.

I joist information

For primary insulation in the walls, I would have wet sprayed cellulose applied since it gives you the most R per $ and is also fire retardant. For the ceiling I would have loose fill cellulose blown in between the I joists to fill them up because it is easily the most R per $. Prior to the application of loose blown ceiling insulation, you would need to have either sheetrock or plywood on the underside of the joists to support the insulation. Insure seams are taped and/or caulked for air sealing. After the ceiling insulation is blown in, you can apply plywood or OSB decking on top for storage space above this room.

I would look out for anything that creates a thermal bridge - concrete or studs. Take a look at mini-split heat pumps for heating/cooling.