Blog Post

Electric Resistance Heat... Really? (live from Greenbuild)

I'm really tired. Does low-voltage electric resistance heat actually make sense? Under the right circumstances, it seems like it might. I see the people from Step Warmfloor at Greenbuild every year, but I never talk to them — frankly, because I have a bias against the concept of their product. This year, I talked to them. And now I have to admit that I'm a little bit confused. Would anybody be willing to take a look at their pitch and either talk some sense into me or tell me that I'm not entirely nuts?

Published November 10, 2009

(2009, November 10). Electric Resistance Heat... Really? (live from Greenbuild). Retrieved from https://www.buildinggreen.com/blog/electric-resistance-heat-really-live-greenbuild

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Comments

BuildingGreen Basic Member

November 11, 2009 - 2:26 am

It's not clear why that cost comparison is based on a 26 MmBTU annual heating load for the WarmFloor analysis, but a 61 MmBTU (for the radiant floors) or 68MmBTU load for the other systems.I believe that radiant systems can cut demand by 10%, but I still don't see where the more than 50% savings comes from when using their system unless they're comparing the cost of a supplemental heating system with that of a primary heating system.

Even with that huge advantage, most of the savings over conventional systems is due to maintenance costs, which they assume is $0 for their system. I wonder what the expected life of this technology is?

BuildingGreen Basic Member

November 10, 2009 - 7:37 pm

Ethan, you've got a great brain. What do you make of this? http://www.warmfloor.com/literature/HANDBOOK/07%20-%20EFFICIENCY/7.3.%20...

BuildingGreen Basic Member

November 10, 2009 - 7:09 pm

I can believe that this product is extremely efficient at converting electric energy to heat; after all, resistance heat is typically 100% efficient in terms of site energy. The only improvement that I can see them claiming is that the material self-regulates, so that it tapers off consumption as the floor gets up to temperature. This is a tighter feedback loop than you can achieve with a single thermostat, which typically oscillate between the too-high and too-low boundaries (a degree or two above and below the "set point").

However, I'm not sure if flattening the maintained temperature really represents a significant proportion of the total energy, and I suspect it becomes less significant as the heating load increases. Hopefully you don't have to give up the ability to program a custom set-point (including set-backs for unoccupied periods) because the material is intrinsically self-regulating.

The low-voltage is only relevant in the context of off-grid homes, as far as I can tell; it doesn't bestow any significant efficiency improvement by itself. Radiant heat might allow you to lower the air temperature and maintain comfort, but that's a separate debate.