Planning To Build a Shop/Garage, Insulation Question

[rhunt]

If you are pouring the floor, compact the dirt then put plastic down as an vapor barrier. This will prevent moisture from appearing on the floor once the structure is complete. Make sure the plastic is down before the pour. I have an 40 x 60 shop and the plastic was not done, now occasionally when we have high humidity and the outside temperature is right, we have condensation on most parts of the floor. Just saying!! Bob

 

[Rustyiron]

Moss that looks good but if possible I'd rather the exterior of the block be exposed up at least 8", in the summer it's easy to trim against with a string trimmer or lay mulch up to and in winter snow and melting snow lays against it.

Ideally your foam is on the exterior, everywhere. To handle sun & weedeaters on my foundation, I cast in some nailers into the slab to attach a PT 2x10 along the perimeter at grade. It can be painted later or just left to "grey out" weathering. The wall then was pushed out that 1 1/5" then 2" of foam on the framing.
Insulate with 2" of foam under your slab!

 

[BLSXJ]

I'd like to add to the multiple options you have...

If you want to cool the space in the summer, the mini split is likely the way to go. In floor heat doesn't solve your cooling desire. If a mini-spilt is anything like a Air source heat pump, your probably not going to want to adjust the temperature more then a degree or two.

I would definitely put down vapor barrier and even insulation under the floor

Have you considered Insulated concrete forms? they might be the ticket for some or all of your walls.

if you do decide to use stick framing, one option is to use 2x8's for your sill plate and top plate, and 2x4's on 24" OC staggered. this eliminates thermal bridging, effectively puts a 2x4 every 12" but leaves room for 24" insulation bats.

for your intended use, I'd recommend a 10' ceiling... maybe even scissor truss's

 

[Milo]

...I wouldn't have insulation board between the floor and wall, if that's what you're thinking.

You can solid insulate the exterior of the foundation walls up to grade, insulate under the floor, then insulate the interior of the walls over grade. I don't see any reason you can't insulate the interior with solid from the wall to the floor except you'll have to build out the walls or have a shelf. You're electrician might not like it much.

2x6 for sure, and you could go 2' O.C. to save $$$.

I'd use Green Zip for the wall sheathing and Red Zip for the roof sheathing and tape the walls real good, I only tape the roof if I'm not shingling right away. I wouldn't use OSB on a dog house.

You haven't said what your plan is for the roof system, but I assume you're drywalling & insulating the ceiling.

If cost is not a concern and you want the best there is, closed cell spray insulation is the way to go. It will cost a lot more, but will save in heat and A/C for the life of the building. Plus it adds stability and sound proofing to the building.

Adding up the cost of fiberglass and solid on all the walls, spray might not be that out of line cost wise.

I used 2x6 and Icynene spray foam everywhere for the house, walls, ceiling, and under the floor and the rim in the crawl. Even encapsulated the metal ductwork. It was expensive though and I was hoping to build my shop on a lower budget yet still insulated well. Thanks for the tip on green and red zip I'll look into that product.


Here's a detail of basically what I have in mind as far as insulating the slab. The only differences was to have one course of concrete block exposed above the slab with the stud wall setting on it. Then attach 1" foam board to the row of block and studs on the inside from the slab up, before drywall, to add a thermal break and function as a vapor barrier.
But the more I think of it the way this is insulated It makes sense to just make sure the floor level is minimum 8" above outside grade and start the stud wall right on the slab. I would still like to use foam board on the inside.

If you are pouring the floor, compact the dirt then put plastic down as an vapor barrier.

Thanks I plan to use 4" of gravel covered with rigid foam, then plastic before pouring, Bob.

I'd like to add to the multiple options you have...

If you want to cool the space in the summer, the mini split is likely the way to go. In floor heat doesn't solve your cooling desire....
I would definitely put down vapor barrier and even insulation under the floor

Have you considered Insulated concrete forms? they might be the ticket for some or all of your walls.

if you do decide to use stick framing, one option is to use 2x8's for your sill plate and top plate, and 2x4's on 24" OC staggered. this eliminates thermal bridging, effectively puts a 2x4 every 12" but leaves room for 24" insulation bats.

for your intended use, I'd recommend a 10' ceiling... maybe even scissor truss's

That was my thinking as well for a mini-split.

I thought about ICF but feel all things considered that stud walls will work best. I like the idea of 8" plate with offset studs, other than loosing 4" inside all around the building. Was thinking 9' ceiling but might go 10.

 

[BLSXJ]

My old shop had 11'6" ceilings, my current shop is around 8'8".

my current shop looks to have been built, like you describe, stud walls on 1 row of block. But I think the builder screwed up and cut his studs at 93", and didn't account for the second top plate. so my wall height is 1 block + 1.5" sill plate + 93" stud + 3" of double top plate. OR 97.5" of stud wall on top of block.

This has made for some ugly numbers when the ceiling has 3/4" strapping and I only have 96" of wall board.

So this leads me to recommend either a true 96" stud wall, or jump up to 120" stud wall (a 9' stud wall will cost the same as the 10') and having the extra height will be nice if you want to install a 8' tall garage door. (encase your tractor ever grows!)

 

[Barnbuilder]

Was reading an article in a Fine Homebuilding magazine. Called a EP&B wall. They use 2x6 top and bottom plates. 2x4 studs flush to inside of wall. 2" XPS rigid foam board on top of studs which then becomes flush with outside of plates. OSB nailed over all that and then moisture barrier. Not having the studs extending to the outside prevents thermal transfer. Has an R-23.
Just another idea.

 

[Milo]

... But I think the builder screwed up and cut his studs at 93", and didn't account for the second top plate..... This has made for some ugly numbers when the ceiling has 3/4" strapping and I only have 96" of wall board.

So this leads me to recommend either a true 96" stud wall, or jump up to 120" stud wall (a 9' stud wall will cost the same as the 10') and having the extra height will be nice if you want to install a 8' tall garage door. (encase your tractor ever grows!)

Good point BLSXL I've always used full 8' studs, not the common 8' precuts which are 93" to allow for the top and bottom wall plates which when allowed for give a 96" height. 8' and 93" precuts are the same price.

In the various houses and shops I've had over the years I've found 9' ceilings about perfect for my needs. Tall enough for ceiling fans, above cabinet storage space, taller entry doors, recessed or flush mounted lights are not too high up, and common 54" drywall sheets work well.

I'm way too short sighted to be thinking about my next bigger tractor!

Was reading an article in a Fine Homebuilding magazine. Called a EP&B wall. They use 2x6 top and bottom plates. 2x4 studs flush to inside of wall. 2" XPS rigid foam board on top of studs which then becomes flush with outside of plates. OSB nailed over all that and then moisture barrier. Not having the studs extending to the outside prevents thermal transfer. Has an R-23.
Just another idea.

Thanks Barnbuilder this is a great suggestion! Only question is since I need the moisture barrier on the conditioned side would it make sense to offset the studs to the outside and attach the rigid foam board on the inside?

 

[Navvet]

I'd like to add to the multiple options you have...

If you want to cool the space in the summer, the mini split is likely the way to go. In floor heat doesn't solve your cooling desire. If a mini-spilt is anything like a Air source heat pump, your probably not going to want to adjust the temperature more then a degree or two.

I would definitely put down vapor barrier and even insulation under the floor

Have you considered Insulated concrete forms? they might be the ticket for some or all of your walls.

if you do decide to use stick framing, one option is to use 2x8's for your sill plate and top plate, and 2x4's on 24" OC staggered. this eliminates thermal bridging, effectively puts a 2x4 every 12" but leaves room for 24" insulation bats.

for your intended use, I'd recommend a 10' ceiling... maybe even scissor truss's

Wow !!! Some one who thinks like I do, Amazing ........

I just finished a 24' X 30' garage and built it with 2x6 top and bottom plates with 2x4's every foot staggered in and out. Not only structurally sound but great for insulation, and wiring and air hose system inside the walls were a snap. Our local building inspector was so impressed with the garage he brought several contractors over to see what I was doing.

Also, if you look under http://www.tractorbynet.com/forums/projects/390012-shop-heat.html you will see my opinion of the mini-split systems (especially the Mr Cool DIY series of ductless mini split).

 

[Milo]

I just finished a 24' X 30' garage and built it with 2x6 top and bottom plates with 2x4's every foot staggered in and out. Not only structurally sound but great for insulation, and wiring and air hose system inside the walls were a snap. Our local building inspector was so impressed with the garage he brought several contractors over to see what I was doing....

Interesting. What did you use for insulation?

 

[Navvet]

Interesting. What did you use for insulation?

I used standard R19 fiberglass batts. 23" wide so they attach to the "inner" 2x4's and i split the outside with a knife to wrap around the "outer" 2X4's .

I built it with 9' walls and a 12' arched ceiling to accommodate a 10,000 lb lift (for the cars, bikes, etc.)

A 1.5 ton ductless mini split heat pump keeps the temp at 70 year round.