Electric vs. hydronic in concrete slab heating.
My wife and I are planning to build a house in the mountains of central Idaho…definately snow country. We’re planning on slab on grade(with 24″ below grade footers/stemwalls) with finished concrete floors. We want to include some sort of in slab heating. A hydronic system, with an electric boiler seemed to be the first obvious choice as that has become fairly commonplace for new construction in this area. Let me note that electricty is fairly cheap here (about $0.05/kwh) and natural gas is not an option.
My electrician, and a couple of friends have been trying to sell me on an electric in floor heating system, namely one marketed by Applied Radiant Technologies. They have all installed it in their houses (all less than 2 years ago) and love it. I also know people with hydronic systems that are just as happy.
The materials and instalation costs of the electric system are way less than half of that of a hydronic system…which makes it very attractive to poor working slobs like my wife and I…but I have some reservations.
I haven’t found a way to make any direct comparisons between the effiency or performance of the two systems…too many variables, seems like comparing apples and oranges.
I’m also wondering if I should be concerned with the effects a possible electro magnetic field would pose to radio/television recption or long term health effects, even though the cable is shielded?
If anyone out there has any experience, opinions or just plain gut feelings, I’d love to hear from you.
Thanks
Replies
I'm not familiar with the systems enough to compare function. But, from an efficiency point of view, if you use electricity in both alternatives, the operating cost would be very similar. With electric heat in the slab there would be no heat loss (except what went into the ground). With electricity heating the water, since there is no chimney as with fuels, there would also be next to no heat loss (except for the ground). So, from an operating cost standpoint they would be equivalent.
As for the electric fields, I read a technical article some years ago published by the IEEE, the national electrical engineering organization. They had examined the issue of electromagnetic fields. Their conclusion was that there were no well done studies that showed a link between electromagnetic fields and any disease. There was also no plausible theory as to why low level fields might cause harm. The amount of flux a person would generate walking around in the Earth's magnetic field is greater than would be generated by living underneath power lines. I don't know what the recent knowledge is.
For low cost operation, it's critical to have the house well insulated. The minimum recommend insulation under a slab is 2", but some experts recommend 3 or 4. Of course, the whole house should be well insulated.
1) EMR: the electrons in the wires are going back and forth at 60 Hz. Your TV, radio, computer, etc operate at Kilohertz to megaHertz to Gigahertz. 60 hertz looks like DC to them. Like the butterfly that does not see the redwood change during its lifetime. Not a problem.
2) Install: electric should be cheaper. Zoning should be more flexible
3) operating cost. At $0.05/kwh, you pay $1.46 for every 100,000 BTU used in your house (100% eff). To equal that propane (at 85% eff) would have to cost $1.09. Fuel oil (at 82% efficient) would have to be $1.28 or less. Historically, those fuels have been close to that and over the long term, electric rates rise if fuel rises. So I, personally, would ignore current pricing and bet on fuel oil in the long term. But this year, electric at 0.05/kwh would be far ahead and if you are constained in your capital budget, then electric might the way to go.
You could hedge that bet with a propane HWH ($250) in addition to the electric. Really fast recharge rates, the option of switching from one to the other as costs change and some redundacy in case one unit goes out on a cold winter night. The HWH could go to a small kick-space heater or baseboard units to provide partial redundacy and a quicker response that the electric RFH on its own.
The hydronic system would have the advantage in that you could change boilers or type of fuel in the future, maybe even tie in a solar collector to help ease the cost of heating in sunny, though cold, Idaho. Just make sure you insulate the slab. Also, make sure you use tubing that has an oxygen barrier, if going the hydronic route - very important.