Shop 14x25 - True Comfort electric radiant heating floor

Snowdreamer

Getting little solid info about this application - asking for advice from the collective. Making a new shop 14’x25’, need it only to hold ‘comfortable’ temp for my use (i.e. not tight residential temp). Will be VERY well insulated SIP walls and ceiling with as good overhead doors on both ends as I can find. Concrete slab will be 3” think with 2” insulation underneath and around perimeter. One personnel door, only windows will be one panel in overhead doors. Have had many hydronic radiant slabs before. Really like the potential simplicity / efficiency of electric radiant heat. Heavy duty cables made for in-concrete are custom and slow fabrication. Thinking of using lighter cable True Comfort cables set into Kerdi-Board at bottom of concrete slab, to protect during pour; also wire mesh in middle of slab. Don’t know why this won’t work fine to HOLD slab temperature through winter. I realize it may not be able to heat up from frigid by itself, won’t need that. Calcs are that I might need 2,500 W max which is close to rating of cable. Can supplement in crazy weather with extra space heater. Location is temperate Vancouver Island, but still Canada. What am I missing in this plan? Thanks in advance, Randy

Jamie Hall

The concept sounds good, but two questions. First, what are your electric rates like? You're going to use a fair amount of electricity keeping the place warm…

Second… um… what type of shop? Wood working? Or automotive/truck? Wood working you three inch slab will probably be fine. But the overhead doors talk to me about vehicles… and a three inch slab isn't going to manage very happily.

Snowdreamer

Electricity is the only real heating option. Wood out of style here now, propane introduces a whole new system, nat gas not available there - so electricity. Does a radiant system use more electricity than hydronic or overhead radiant? I’m thinking the electric resistance cable has a pretty ok conversion efficiency rate. Cost is not the overall most important factor, I want convenience / ease / low maintenance. Shop is general retired putzing shop where a bit of everything could happen; but vehicles will stay outside. Mostly some good woodworking tools. Slab 3” will be ok, trying to keep its volume down but enough to be strong enough for use. Good Qs.

hot_rod

so 14X25= 350 sq ft WAG of 20 btu/ sq ft = 7,000 btu/hr on coldest day

Load could be lower depending on your design temperature and what temperature inside you want 65- 67°F is a good working temperature in my shop. Garage doors are the weak link for R-value and sealing against wind.

I would still use 1/2" pex so you have heating options. electric, LP, wood boiler, hydrogen, micro nuclear :) Pex is repairable, not so much with resistance wire.

A small a2whp would be a nice way to go if electricity is to be used most efficiently. Viessmann has a 1.5 ton, that is what I heat my shop with. Maybe even a HPWH ducted outside.

pecmsg

even LP hot water would be cheaper then straight electric.
look it up

https://coalpail.com/fuel-comparison-calculator-home-heating

hot_rod

a quick search shows about .15 for power, with a base monthly of $48.00? What is delivered LP. Can you own your own tank, or are they all leased?

While radiant floors are the Cadillac choice, a small mini split would heat and cool , allow quick ramp up and down and cost a fraction of the cost.

My first choice is still radiant floors, for standing and working on.