Workshop build insulation advice
![](https://secure.gravatar.com/avatar/5048c489de181ba5aaec585eee192601?s=52&d=https%3A%2F%2Fimages.greenbuildingadvisor.com%2Fapp%2Favatars%2F200x200%2Fi.png&r=g)
Greetings!
I’m currently designing a 30′ x 24′ x 10′ woodworking shop here in Vermont and wanted to get a little advice on the insulation methods I’m considering.
I’m thinking of the following for the walls:
Metal cladding (vertical)
2″ rigid blue foam
OSB sheathing (exterior)
2×6 framing
R-23 mineral wool (or blown on cellulose?)
Plywood sheathing (interior)
I believe this should give me an R-value of 36 for the walls.
For the ceiling space, I’m thinking 16″ of blown in cellulose for an R-50 rating?
The space would be heated and cooled by an 18,000 BTU heat pump.
Does all of this sound reasonable? Is any of it overkill?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
![](https://www.greenbuildingadvisor.com/app/themes/greenbuildingadvisor/dist/img/modules/detail-library/thumb1.png)
![](https://www.greenbuildingadvisor.com/app/themes/greenbuildingadvisor/dist/img/modules/detail-library/thumb2.png)
Replies
Ian,
The blue foam is probably XPS -- and green builders try to avoid using XPS for environmental reasons. Either EPS or polyiso is better. More information here: "Choosing Rigid Foam."
You are planning to install R-10 of continuous rigid foam on the exterior of your 2x6 wall. In Vermont, that's not enough R-value to avoid moisture problems. More information here: "Calculating the Minimum Thickness of Rigid Foam Sheathing."
Thanks, Martin. Appreciate the quick reply and links.
Ian,
Getting some insulation on the floor would also make a big difference in comfort in the winter. If you are heating the space all the time, best is bellow the concrete pad or if you are heating it only when needed, than above the concrete pad. Even 1" would make a big difference.
I would also suggest some high windows, say foot tall along the wall a bit bellow the soffits. South facing would make a big difference in winter energy use but could create glare issues, north facing would bring in great diffuse light all year around but would cost a bit of extra heating. High windows also keep the walls free for equipment/storage.
Unless you are occupying the shop full time or humidifying it in the winter, I wouldn't worry too much about condensation in the walls. The guidelines Martin suggest are for houses, in a workshop without a humidity source, the inside air quickly becomes as dry as outside air eliminating the condensation issues.
Also be careful if you put in a roll up garage door. Those can be quite leaky and a big energy loss.
I've had much better luck with building bi-folds out of insulated exterior door slabs and using standard exterior door weatherstripping/sealing/doorjambs. Bonus is you can use it as a normal entrance door and also get double pane glass inserts in them for cheap for a bit of additional light.
Thanks, Akos.
We have 2" of insulation under the slab, so should be all set there.
The high windows are an interesting suggestion and something I might look into.
Hi Ian,
A heat pump would work in a shop. Some considerations;
Dusty, dirty, solvents, wont go well with a heatpump indoor unit.
Second, if your going to be opening a large door for any extended period of time in the peak winter (more then carrying in a few supplies) your pickup factor has to be accounted for. Radiant heat holds its heat in mass (ie concrete shop floor). Heated air will flow right out a door when opened.
Consider a WWSD (warm weather shut down) on the appliance for heating season using a relay to turn off the unit above 55-60f.
Good to know about the heat pump, Moe.
We plan on having an explosion proof extractor fan at the opposition end of the space for spraying so I'm hoping that won't affect the heat pump. We'll also be paying very close attention to dust capture and removal.
Here's a fairly simple SketchUp model I'm working on. It's my first time using the software.