Cost of heating a shop

   / Cost of heating a shop #1  

5030tinkerer

Gold Member
Joined
Dec 27, 2005
Messages
432
Location
Iowa
Tractor
Kubota GL3830/GL5030
Hey guys - I'm trying to decide between an insulated pole barn and a polyurethane Structural Insulated Panel (Thermocore of Missouri) R40 wall and ceiling building with R10 or so floors.

I had already been sold on the SIP concept, but now I'm not sure if it makes financial sense between the cost of the panels, foundation, etc. Any idea what the cost difference of keeping a 40x70x16 insulated pole barn (Maybe R19 walls and R30 roof with R10 underslab) with another 20x70x8 usable up top in a gambrel section heated and cooled vs an uber-insulated SIP structure in a colder climate like Iowa?

Cost per kwh is $0.0349/kwh in the winter (after the first 1,000kwh @ $0.07741/kwh) and $0.08772/kwh or so in the summer. Crazy cheap utilities, I know, but these costs will only go up as time goes by for sure.

The shop will be used daily, so climate control would be daily.

Very interested in any cost ideas on keeping the entire structure at 73 in the summer and 68 in the winter. Maybe the first step is to perform a heat load calculation, but that will only tell me sizing of HVAC equipment - I think - and not true costs to keep it comfortable in there (again, as far as my limited knowledge of things goes). Then, of course, there's the whole 'true' R-value discussion. Yikes! Call me confused!

Also interested in seeing what happens (if the numbers bear out another way) with an option of keeping a smaller upstairs maybe 600 sq ft (4800 cu ft area) 'truly' conditioned at 73 in the summer and 68 in the winter, leaving the remaining 3600 sq ft (51200 cu ft) at 80 degrees or so in the summer and maybe 60 in the winter.

Structure will have four R25.8 14H x 16W OH doors, one R11 3'0 service door, and 10 U-factor 0.14 3'x4' casement windows. Heat source will be radiant in the 40x70 slab with an electric boiler along with possibly mini-splits for AC and supplemental heating.

This is a ton of info, I know. Truly - any and all help VERY much appreciated.
 
   / Cost of heating a shop #2  
I think you will want more insulation. R30 in the ceiling isn't very much. R42 is standard and some are doing R48 or more.

Your electric rates are "crazy cheap" , I haven't seen under 10 cents per kw since the '80's. Mine are about .15 after adding tax and the other fees.

I keep my 30x46 garage heated to 42 degrees and fine it is easy on the wallet. It starts to get expensive when I get over 55 degrees so I don't do that very often. Besides, anything over 58 is just to hot to work in. I end up turning the fans on to keep from sweating.

I bought my overhead door from The Door and Fence Store in Ames. Their 3" thick door is top of the line, and a little pricey, but well worth it I think.
 
   / Cost of heating a shop #3  
I find temps around 60 fine for working. I like to put a pair of denim un-insulated coveralls on for a lot of jobs, and normal room temperature is too hot for that.

One option you didn't list is on-site spray foam. I don't know if that is more or less $$$ than SIPs for the R-value you want. Cutting down air infiltration is really important with that much exposed exterior wall area. Spray foam should be good for air tightness, plus it provides the vapor barrier.

It is probably worth the effort to do a heat loss calculation with various wall methods, foundation and insulation R-values.

The residential conversion for electric to heat is 3,413 btu's per kWh. Knowing your btu loss per hour would allow you to roughly project the kWh's needed to maintain the temperature. There is probably a web resource somewhere that rolls your location heating & cooling degree days into some kind of formula. Maybe someone knows of one that is useful.

Years ago I tried some free programs but my ability to get all the input parameters correct was doubtful enough that I didn't think I would have much faith in the answers. Much like "garbage in, garbage out." :laughing:
 
   / Cost of heating a shop #4  
The install cost is higher, but I would put in a heat pump. At those electric prices, you could do a quick heat with the electric backup and let the heat pump maintain. You could mount the air handler from the ceiling w/o ducting to blow into the shop, with a filter on the return (like the oil/gas heat you often see in garages. Good cheap heat.

paul
 
   / Cost of heating a shop #5  
So I had to do the math for my vacation home. Key was paying for a Manual J calculation. Part of that includes the amount of glazing and the orientation of the home. Since I live on a mountain (hill out west) top, I had to find a comparable location. Our valley is AC intensive, my location is heat intensive (300 Ac hours/5500 heating hours).

First thing I found from the Manual J, was every HVAC guy I talked to wanted to provide me double the capacity I needed. Means more money, higher humidity, and more cost to run (73/68 work with normal humidity).

When I tried SIPS in 2010, the exterior sheathing was an issue. I did traditional build, spray foamed the edges and penetrations of the stud walls and ceiling, then blew cellulose as the primary insulation. I had 2 x 6 walls. Goal was R20 walls and R 50 ceiling.

Made one costly mistake. I layered R10 foam insulation panels, and they developed rampant mold between them. Tore them out and spray foamed my air conditioned crawlspace walls instead. Very happy. Need fire retardant paint to make the foam up to code.

SIPS may be more user friendly now.

Bottom line: do the Manual J first with the different types of insulation. It will give you the payback, and help you manage your other costs.
 
   / Cost of heating a shop #6  
I heat my shop in the winter and have ac in the summer, necessary because of the precision machine tools. I did in floor PEX zoned heating and heat the entire shop (20 x 60) with a 50 gallon propane fired HWH and one feedwater pump circulating RV antifreeze through a Califfi manafold system. Costs me about a grand a winter and a grand a summer for 2 window ac units. 15 in the walls, 30 in the ceiling (between the trusses) open ceiling (has to be, I have an overhead rail/trolley crane). 15 in the floor and foam in the rat wall. The slab is 9" thick with steel mat and the PEX is stood off the mat with the pour on top leaving the piping about 4" under slab.

I run my feedwater pump with a Honeywell remote sensor T'Stat with the sensor in a thermowell in the slab about 20" from the sidewall. conviently under the HWH. I hold my floor tempature at a steady 70 degrees all winter. Ambient changes but the floor is always warm and any objects radiate the floor heat. To mitigate up time, I start the system on the heat cycle in early September to take afvantage of soil temperatures from the summer. Once the slab is at 70, the feedwater pump cycles on and off, running about 12 out of 24 hours no matter how cold it is outside. The HWH runs independent. I keep the standing fluid temperature around 140 degrees and system pressure (closed loop) at 7.5 pounds. I have a tempering circuit in the feed loop to intriduce heat stripped fluid back into the feed side to mitigate thermal shock and allow the system to run in smooth remperature gradients.

Been running the system for 5 years now without a hitch. I actually take advantage of the cool slab (compared to outside ambient) in the summer by opening the tempering circuit entirely and closing off the heated fluid feed side and allowing the PEX to circulate cooled fluid in the slab, normalizing the temperatures in the shop. I still maintain a closed system and keep the static pressure at 7.5 pounds.

Best investment in heat/cool I ever made and I put it in myself.

IMO, thats the only way to go.
 
   / Cost of heating a shop #7  
I too would say look at the closed cell foam spray on, and add a 2nd layer of open cell foam on inside with a final top coat to fill up to level with closed cell.

lots of ways to do it, the polystyrene can mold between layers if moisture gets in between wood and it.

Mark
 
   / Cost of heating a shop
  • Thread Starter
#8  
Lots of good information here. Thanks guys!

Good snag on the insulation amounts quoted especially on the ceiling. I'll bump it up! The real question is what the monthly cost difference would be for heating/cooling a SIP (way tight) vs pole barn (much less tight with less 'effective' R values) structure of this size. I'm trying to justify the SIP path on the numbers alone - something that may not be possible.
 
Last edited:
   / Cost of heating a shop #9  
Spray foam it. You live in Iowa so go geothermal.
 
   / Cost of heating a shop #10  
I think a big factor will be the type of openings and how they are used.

The SIP big advantage is how well "sealed" the building is - do a heat load calculation and you will find that most heating $'s are for incoming air through doors, windows, cracks etc in the envelope. The SIP will minimize this, but if you have several large overhead doors and they are open for any period of time the delta you see with the SIP vs the standard pole barn insulation approach will be minimal.

Spray foam in the pole barn will help seal up the package but same concern related to openings.

To get your answer for cost you will need to do a load estimate to determine expected power usage and then apply electricity cost and mechanical efficiency ratings to determine net cost and delta.

I have thermocore SIPs on my house and absolutely would use them again - that said they do nothing for me where I have windows and doors and in my heat load analysis my power requirements for the package associated with heat transfer through the walls using SIPs vs blown cellulose was ~ 10% of total.
My heat load for air infiltration (assumed a very tight house with SIPs -.6 ach, and typical for blown cellulose - 3 ach) was 40% of total for a delta!

My neighbors pole barn sits high on hill like my house and when the typical 30+ mph wind is blowing here I find very few breezes in my house, his pole barn though (with large blanket fiberglass batts and minimal caulking) it is very windy inside the building with doors closed (obviously not 30mph windy, but feels like fans are turned on).

My key point is to focus on sealing the building 1st once that is covered then you will start to see benefit with higher insulation value although diminishing return - the SIPs can help seal the building but at a cost, and if the building can't be sealed (due to many openings etc) then I wouldn't waste the $'s for the SIPs.
 
 
Top