Programmable Thermostats and Radiant ??

Not sure if this will help. But I have my kitchen done with staple up. It's controlled by a probe in the floor. At this time of year I set the probe at 77. The floor won't reach 77 till very warm days of spring. Than i set it at 72/74. no wall t-stat. IMO, a wall t-stat is not ideal for my situation.

Your HVAC guy told you what I've been told as well. Radiant (at least infloor) is not a fast responding heat. I figure even though your floor does not have the "mass" as a full tube in slab might have, your programable t stat will prolly work the heck out of your on demand for quite a while trying to bring the concrete and plywood and all other "coverings" up to temp and then try to reach the tstat to satisfy it. Where setting it and forgeting it will only require occasional bumps during the day. I would guess that this will result in energy savings over the programable. Now I may be wrong is your setback is only a few deg.
I have a full slab w/radiant and it's amazing to watch the relays open for only a few (ok, maybe 5) minutes to keep my techmar t stats happy.

Supposedly the Generation 2 of those crazy expensive NEST thermostats will LEARN how long your slab takes to get to temp. It will also use the internet to determine if it's going to be sunny and have a bunch of solar rise each day.

I haven't found myself with 250 bucks burning a hole in my pocket.... yet.

JP

I can shed some light on this. I have six zones of radiant. I was also told that night setback was a big "no no" with radiant floor heat for the same reasons you mention. However, I've done it, but not for the energy savings aspect of it. Actually, you can't really setback much with radiant and you won't save much energy, IMO. I used my programmable stats purely to have warm floors in the morning. At night around midnight I would set the space back 1 or 2 deg. At 5am I would set the space setpoint back to normal setpoint or 1 deg warmer (depending on the zone). This would ensure I would have nice and toasty floors at 7am when the family is rolling out of bed. Programmable stats give you the flexibility to be creative with your system. For the small cost increase I say go for it.

I think you can sucessfully do it, but it may be something like setback at 5pm for you to notice the actual temp drop by bedtime. Set back up to temp at like 3am for morning temp. I don't think the energy saved will be much, but it would be something. Of course as the outside temp drops and depending on solar heat gain, those times could go either way a few hours. Basically set it on 68 and forget about it, unless you are going away for a long time. The nice thing about radiant is that you are actually comfortable at 68F vs 72F with temp swings.

TS