Radiant floors

ljcrochetDecember 1, 2012

We are in the process of redoing out kitchen and master bathroom. had radiant heat put in the floors. Not finished yet, still need them to have the thermostats installed. Right now the plumber is planning on installing manual thermostats. Said there is no need for a programmed thermostats with the radiant heat.
I was wondering what your thoughts are on this.

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Sophie Wheeler

Because of the large thermal mass that a small amount of wattage is attempting to overcome, it has such a lag time that a setback thermostat isn't really advisable with it. It takes at least an hour or two to come up to temp or to cool down. A manual is a better choice.

    Bookmark   December 1, 2012 at 9:36PM
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You're renovating a kitchen and a bathroom, the 2-most expensive renovations. You're installing radiant in-floor in both and you're going to cheap out on the cost between a programmable and non-programmable thermostat! That doesn't make sense. A prospective buyer of your home may also think that.

There are other advantages of the programmable thermostat. They are, in addition to programming, smart recovery, time, day, backlighting, hours of use by day week and month, floor temperature or air temperature to name the ones I can think of.

We installed radiant in-floor with our bathroom renovation and frankly don't even use it - but I'm still glad we chose the fully programmable one for resale value and some of the other useful features mentioned above, but that's just me...


    Bookmark   December 2, 2012 at 12:21AM
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Ha, you think an hour or two is extreme?

That's how long it takes in my house with a gas furnace. If it takes less time for you, your equipment may be oversized.

    Bookmark   December 2, 2012 at 5:33PM
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We had the same discussion with our HVAC contractor. He said that with hot water radiant heat, just keep it at a constant temperature, because you can't heat a room fast enough from a setback with radiant floors. It's working fine, and we're glad we followed his advice.

He also suggested that we take out the setback thermostat on the rest of the house, which has radiators, for the same reason. But in this case, we left the thermostat but do not use a big setback. We haven't tested it, but I bet that it wouldn't matter if we did.

    Bookmark   December 2, 2012 at 10:04PM
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I disagree with the advice about not using a setback if you have radiators. A hot water or steam system should recover fairly quickly. If this is an older house then there is a good probability the system is oversized. In that case the recovery is even faster.

    Bookmark   December 3, 2012 at 8:01AM
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fsq4cw: I'm not trying to cheap out. If I was I would not have come here and asked the question.
The plumber said that the setback thermostats are not worth having with the radiant heat. Wanted to hear from people who used the radiant to see if they agreed with him. Right now he is giving is really cute round manual thermostats.
We do have baseboard heat in the rest of the house with programmable thermostats, and it had never crossed my mind not to get them for the kitchen and master bathroom till he told us they didn't work well with the radiant heat.
I'm still not sure I understand why, since it is the hot water that runs through the pipes just like the baseboards.

    Bookmark   December 3, 2012 at 8:32AM
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How long does it take to warm up the kitchen or the bath from the time you turn up the heat? In the case of the bath, if you shower and shave in the AM after waking, it might be nice to have a programmable thermostat.

I have heat lamps in my MBR bath. They take about five minutes to get the bathroom toasty warm. I did not install a programmable thermostat - just On/Off switches.

In the case of the kitchen, I again would want to know how long it takes the radiant heat to work its magic...

This post was edited by saltidawg on Mon, Dec 3, 12 at 10:18

    Bookmark   December 3, 2012 at 9:17AM
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I apologize for coming across too strong; I'm sorry.

You can go either way programmable or non-programmable set and forget it and be happy either way. Programmable with smart set backs will allow you to set back the temperature yet deliver the desired set point when you want it without additional calculations on your part.

I'm sure you'll be happy with whatever you choose.


    Bookmark   December 4, 2012 at 12:30AM
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The obvious point is that a setback will help. Depends on how much you want to save. In the kitchen, it will cool at night if you set it that way and it will save money. Not as much as a heating system with a fast recovery but it will still save.

People in the trade don't necessarily care about your dollars going forward - it just isn't their priority. Avoiding callbacks is....

    Bookmark   December 4, 2012 at 6:19AM
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Do you have a recommendation for a a good programmable with smart set backs?

    Bookmark   December 4, 2012 at 11:09AM
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The amount of savings that you will have with a programable thermostat depends a lot on your lifestyle. One one extreme, you are out of the house a lot for extended periods, like it cool at night when you are asleep, and make heavy use of some rooms and not others, a set-back will be very beneficial. If someone is home all day, tends to move between all the rooms spending meaningful time in each room and likes to sleep at the same temp as when awake, what would be the point?

I am in the former pattern. In many climates, over the years, I have heated or cooled the house for very few hours each day. There is just no point in keeping the place that comfortable if no one is there to use it. I have a heat pump mini split in my utility/laundry room. I've used it more often to make sure it still works than to control the climate. Sometimes I wonder if I should have spent the coin to install it, but my patterns could change.

Keep in mind that the HVAC equipment suffers less wear and runs more efficiently when it is running for long periods to "recover" rather than snapping on and off all day/night.

Maybe the OP's plumber's family lives like the latter category and can not get his head around anyone else's situation.

    Bookmark   December 4, 2012 at 2:10PM
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I'd be looking for a RELIABLE programable thermostat. They can be expensive and not last that long negating any energy savings with replacement costs. You might consider one that can be operated remotely via internet. That way if you change plans and arrive home earlier than expected, you can change set points and have it comfy when you arrive home.

    Bookmark   December 4, 2012 at 2:14PM
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