Hi,

I am building a detached garage - total dimensions of 32x34 feet. The floor will be poured concrete. It will be segemented as follows:
8x34 will be a laundry room, dog, mud room. The remaining 24x34 space will be a standard garage. We would like to have the temp in the standard garage space above 38 - 40 F. We don't want items to freeze. In the laundry room we would like to have it in the 45 - 50F range. The structure would be insulated. In Oregon we pay about $0.07kWh. We get winter in Central Oregon - Redmond. We are considering elec radiant floor heat. It would also have propane wall heaters as a "backup" or to augment. The propane wall heater appliances are cheap. We have a large buried tank on site.

I am trying to do a TCO on the above Elec/propane combo vs Hydronic radiant. It's hard to get my head around the cost of hydronic and all the associated controls for a garage/utility room. Somehow the elec option must be less expensive and easy to operate. After all it's just a garage and washer right? We plan on adding PV at some point.

Any opinions?? Bombs away.

If you put electric cable in the slab you will not be able to change your mind after you receive your first electric bill.

Hydronic - PEX - avails you every option. It costs more for hydronics because it is a better value.

I think a Combi-Cor by Bradford White is in order, and then you can afford to keep the whole place at 50F!

Single zone, no need for backup and I wouldn’t waste time and money on unnecessary antifreeze. Get an inexpensive temperature alarm instead.

MA

No matter what information I offer, you're going to get an argument from the hydro guys. So, I'll offer the design and costs. We can go anywehere you want from there.

I would have the garage as one zone and the laundry, mud and dog space as another. Two digital programmable thermostats using a low voltage cable system with controls mounted in the garage or laundry, your choice. There are a total of 3 control boxes measuring 17" x 12" each and they mount to any standard 16"oc wall. Install the element in both areas on 8" spacing attached to the remesh before pouring. Have the remesh on chairs holding it within 1-1/2" from the surface and insulate below.

Your upfront costs for materials will be around $9.00psf plus shipping.

Based on the $0.07kvh you offered, the garage will cost $0.77 and the mud room will cost $0.31 both per running hour. The system will generate about 50 btu's psf so it won't require much "on" time to maintain. I have a client with a similar garage system (no mud room) in NY and their total running time during the winter is around 3 hours per day to mainatin 45-50* slab temp.

The design includes jumpers for going under the saw cuts/expansion joints so the slabs remain independant. It will not require any maintenance.

This message has been edited. Last edited by: Warmsmeallup,

for a smaller area, the electric systems might be competitive.

for an area this size, a simple control setup, with a low end heat source plus distribution is unlikely to come anywhere near $9/sq ft on 1000sq ft of slab in material cost.

I have no idea how easy electric is to install.. I imagine it's quick. If you're hiring out labor that might affect the analysis as well.

What did you ever put in that garage. Electric radiant infrared or certain electric fan forced units do the trick with a little install/light electrical work, and years of maintenance free use. Would love to hear how you solved the issue.