Insulating an existing concrete block shop

I'm working on convincing the current owner to sell me a vacant 1950's-era service station. Concrete block construction, roughly 15Hx30Wx50L with flat roof. Pretty confident there is little to no insulation in the walls. 

For visualization purposes:

Ideally, I want it to look like a (renovated) old service station, inside and out. Will likely paint interior and exterior surfaces. I think I'd appreciate the thermal mass of blocks on the inside with insulation on the outside. I don't expect it to be hot in the winter or frosty in the summer, just relatively easy to keep a comfortable medium.

Bonus points if adding insulation doesn't cost me more than erecting a brand new insulated steel building of similar size. Which, to be honest, is almost certainly a quicker, easier, and more realistic option than convincing the old fart to sell this heap in the first place.

Cool shop! I've often fantasized about finding an old service station for a workshop. Too bad the glass overhead doors look to be in rough shape, though they're certainly not insulated so wouldn't help with your comfort goals if kept.

EIFS is probably your best bet; they apply insulation lath and a stucco like material to the outside of the building. It's not cheap but can be neat looking if done right. It does hide the current architectural features. They can be replicated in the EIFS but it looks a bit "plasticky" because, well, it is. Poorly done EIFS can be a water retention problem - moisture behind the EIFS can't get out and you end up with mold in there. So take care with your contractor selection.

Replace the doors with modern, insulated versions.

If you want to leave the outside looking more original, fir out the inside walls and insulate as normal.  Cleaning the block and sealing would be a very good idea.

Lower the ceiling as much as practical for the intended use.  The less volume you need to heat/cool, the more efficient your HVAC system will be.

Don't worry about the thermal mass.  If you insulate the outside, you're insulating the block from environmental input.  And if you insulate the inside, you're insulating yourself from the block, so thrermal mass is irrelevant.

Clean and paint the outside with a high quality elastomeric coating to keep weather infiltration down.  Stud the inside with 2x4s at 24" oc, run a lot of conduit for electrical lines, and get the whole shootin match sprayed with foam insulation to the face of the studs.  Drywall over that. The spray foam will skin over and give you a vapor barrier just under the wallboard on the conditioned side of the insulation, which is where you want it.

Put OSB or plywood up the first 48" all around, and up 96" behind your bench locations.

Make sure all old underground gas tanks are gone and any environmental cleanup required has been taken care of before signing any papers.

As for the insulation, I'd worry first about air infiltration - take care of leaks and cracks, weatherstripping, etc.  Then look at insulating the roof first, after all heat rises so that's where most of it will escape.

Frame up the inside and fill it with insulation, use whatever covering over it that you want(drywall, osb etc)

I know here in Fl they do a lot of injected foam in block walls. Not sure this adds much insulation but it does help seal the walls against air infiltration. Fill Foam Insulation

My past perception on commercial corner properties like this is that the property taxes are prohibitively expensive.  

I am sure this varies by state and municipality so your experience may be different but I recommend having a good understanding of the property tax expenses. 

In reply to John Welsh :

Expanding on that some, even if the taxes are currently reasonable compare the current listed market (or appraised) value that the auditor has assigned to the property to what you’re possibly going to pay for the place. Nine times out of ten when you buy a building for more than the auditors market value they automatically bump the market value up to what you paid and the taxes go up proportionally. 

stuart in mn said:

Make sure all old underground gas tanks are gone and any environmental cleanup required has been taken care of before signing any papers.

This can’t be stated enough. There needs to be paperwork from the EPA confirming the tanks have been removed & soil samples taken were clean enough to pass their tests. 

Build a steel building. 

In reply to JohnInKansas :

When I insulated my concrete block portion of my house I had access to a foam company. Their mistakes are ground up and poured into bags. Really big bags, almost fill a pickup bed but extremely flimsy.  Cost was 5 dollars. 

Parts that I could get to the top of the blocks I just poured that foam in and let it settle.  At the bottom I knocked a hole in between the webs on the block and stuck a shop vac with a piece of window screen across the hose.  I kept working my way back and forth filling and sucking each web until they wouldn’t take anymore.  

Parts I didn’t have access to,  I knocked holes in the top row and reversed the shop vac. When I couldn’t get anymore foam in I used great stuff the spray foam in a can to fill the holes.  . It wasn’t a fast process but it really changed the shop.  Not perfect because of the thermal bridging at the webs.  

The exposed part of the basement I put 2 inch foam on with panel adhesive. The Wall was already painted.  I’m not sure it will work on bare concrete.  Then using the same panel adhesive put either Sheetrock or wood paneling over the foam.  

Tanks are out, there was an article in the local paper about 20 years ago saying the current owner pulled them to keep the EPA off his back. I'll ask and get tested anyway.

Taxes are an interesting thought. Current appraised value of building and small lot is around $50k, and if I can't get it for that or less, I'm walking away. Suspect the real kicker will be appraised value after I renovate and clean up the lot. If (and its a BIG if) the owner decides he can sell it to me, I'll want to have a nice long talk with the city/county officials about the whole thing.

I will ultimately wind up in an old building, because that goes nicely with the product I'm planning on selling. A steel building may be in the cards in the short term just to get the ball rolling and keep overhead costs down, but if I can get a decent deal on a corner lot in a small town that anticipates major growth in the next decade...

In reply to JohnInKansas :

Keep in mind that unless you invite the assessor inside they can only assess it based on purchase price plus any improvements they can see from the outside. 

I'm kind of jealous... there was a shop almost identical to that at the end of the side street I live on that I drooled over for the first year and a half we lived at our current house and often joked that I should find out what they wanted for it and buy it to have a real workshop.

A bit over 2 years ago somebody bought/leased it, filled in where the doors were and turned it into a liquor store. I was heartbroken since my pipe dream of a cool shop was gone, but it's nice to not have to drive nearly as far when the Dancer is craving mimosas!

Good info for me here though regardless- my garage is uninsulated cinder blocks, so if we decide that we're going to stick it out and try and remodel/update our current house vs. moving to another place (or, pie-in-the-sky, building a new house & garage) I will be wanting to insulate the garage in addition to raising the roof to allow putting in a lift.