Setbacks and Radiant Heat
No, it is not setbacks in terms of any project, I am referring to setting back the temperature of zones in our house. When we put our system in, we had non-programmable thermostats installed as we were advised that due to how radiant heat works that it was more efficient to keep an even heat in the floors than letting the system cool during times when we don't need the heat.
Well, our gas bills have been telling us that we could definitely be doing more to conserve fuel. So, as a result, we are doing some experimentation with using programmable thermostats with our radiant heat system. Or concrete floors are relatively thin (3" to 4") and heat up surprisingly fast considering how radiant heating works. We have installed one and plan to install another this weekend and we will see how this affects our gas usage. My thinking is that using our high efficiency boiler to keep the pads (particularly in my son's side of the house, were we keep it warmer) a constant temperature is wasting more fuel that it would take to bring the pads back up to temperature after a day away. The added benefit is the floors are actually warm to the touch when we get home, which doesn't actually happen that often when you keep the house at a constant temperature.
Time will tell if this uses more or less fuel, but I suspect it will be a savings. Now, for radiant, our setback is considerably shallower than for a forced air system. We are setting back to about 17 to 18 C during the day, when we are away, and warming up to 20.5 C when we are back. There are a few locations we likely won't use programmable thermostats, such as the basement. There a steady, though relatively cool 19 C is all we need. We will keep you posted.
PM: I think what makes the setbacks effective for us, and my wife mentioned it last night, was that we didn't cover our concrete floor with any other flooring material, such as hardwood. If you had another layer I can see setbacks not being nearly as effective as the time to heat the floor would increase quite a lot. Thanks for the feedback. (03/10/09)
Todd - Home Construction Improvemen: Set back thermostats DEFINITELY work on radiant despite industry "folks" stating otherwise. The HVAC contractors that I use all say set it and forget it. However, after paying high heating bills I too started experimenting and I'm happy to say I've cut my bills down 20%. We live in New England and have no problem setting back 10 degrees at night and during the day. (03/05/09)
PM: I have found that if the the "air" in the house gets below 18 C or so, that the concrete floors actually end up closer to 17 C or less, which puts the chill back in them and makes it less comfortable to walk and stand on (you notice they are cool). Great for the summer, but not so nice in the cool weather. On the whole, though, I love the "feeling" of 19 C to 20 C in the house in the winter. Very comfortable and not at all spiky like the forced air was. (02/09/09)
Gypsy: Well, it also is a comfort thing. Our newly insulated, but not so sealed home, is still set at only 18C during the day (when we're home most of the time) and 15.5C overnight (unless it's really cold out). And that's actually having turned everything up 2.5 degrees overall as I'm not 20 anymore ;P (02/08/09)