Radiant Floor Heating/Cooling Questions
March 9, 2016 2:49 PM   Subscribe

Do you have radiant heating/cooling in your house or have you spent time in a house with it? What was your experience with it?

I am seriously considering getting radiant floor heating/cooling for my house and I have some questions as to how it works in practice. Internet searching for the most part just sends me to people selling radiant systems so it is hard to tell if the info is legit or just marketing. This is for a new house and not a retrofit situation and about 3,000 square feet (280m2) in total and I am in Toronto where the temperature is at its coldest in the winter -20C/-4F and at its hottest in the summer 35C/95F and humid.

First off, flooring materials. Our preference would be for wooden flooring. I understand that regular hardwood isn't recommended for radiant heating but engineered hardwood is OK with it. How does wood perform compared to tile as far as its ability to control the room temperature and energy usage? My only experience with tiles are for non-heated ones and only in hallways, washrooms and kitchens. If we get floor tiles, will the fact that the tiles are warm make them more comfortable to walk on in bare feet/socks? How does a warm tile floor compare to a wood floor for comfort? Are our feet going to get tired being on a hard surface all the time? In general I get that if things drop on tile/stone they're more likely to break than on wood, but on the other hand I'll worry less about someone dragging a chair and then ruining the floor. We have small kids so things dropping and general rough treatment is to be expected for the next few years.

Second, how effective is it at keeping the house cool? We're in Toronto so in the summer we get highs in the low to mid 30s (around 90-95F). Will radiant cooling and open windows/fans be able to keep up or would we need separate air conditioning units as well? We don't use the AC too much as is and are fine with the indoor temperature being around 25C (77F).

Are there any neat features/extras that can be done with radiant heating/cooling? I understand that you can have towel warmers put in the bathroom that are hooked into the system, are there other things like that?

My understanding is that radiant heating/cooling is more energy efficient than a forced air system. I am less concerned with ongoing energy costs but in practical use how much of a savings on my gas/electric bill would I see in a radiant system? The alternative to the radiant floor heating/cooling would be a high efficiency heater and AC unit and this is in a house which will have good insulation and windows.
posted by any portmanteau in a storm to Home & Garden (25 answers total) 3 users marked this as a favorite
I house-sat for a week at a time, for several different weeks, at a house in Philadelphia with radiant heating via floor tiles. My experience was that I was cold all the time. It is warm on the feet, but the air surrounding me never ever felt warm. From that I learned I would not want to use this system in any future home. Maybe wood would be more comfortable, but I am just not sold on the concept.

There are so many variables to heat that I hesitate to make a recommendation. However, I can say that right now I live in a flat that's about 1600 square feet. We heat it with a 2012 model gas-efficient heater that pushes forced hot air. With balanced billing, I pay about $70 a month year round to heat the place. That is the lowest heating payment I've ever had, and I credit good windows, thick walls, and that new model heater.
posted by Miko at 2:56 PM on March 9, 2016

Response by poster: Do you know how the insulation/windows were in that house? Like was it a newer house with double/triple paned windows and lots of insulation or was it an older one where they had either an old system or a retrofit to put the radiant heating in but not great insulation otherwise so the heat could escape?

Also, did adjusting the thermostat help or was the air still always cold?
posted by any portmanteau in a storm at 3:05 PM on March 9, 2016

It was actually an unusual house. It was an older (1920s) house that was sort of an architectural landmark, made of poured reinforced concrete, so very insulating. However, when I worked there it had had a full recent restoration to mid-90s standards. The windows, I'm not sure. They were architectural, a lot of them, and might have been restored historic windows in which case probably not a fantastic seal. But the kitchen wing was new so the windows were too, and that was also pretty cold. It's a little hard to judge how that would all translate.

did adjusting the thermostat help

In this particular house, no, at least not over the course of a week. That may be partly because of the volume or the concrete, but since it wasn't circulating air I'm not sure we can blame that too much. The only thing that seemed to provide real warmth there was passive solar. It might be too much of an outlier of a house.
posted by Miko at 3:17 PM on March 9, 2016

I'm not at all certain of how the prices compare in your specific situation. I think you should get a local consultant.
1 1/2 years ago, I changed from an oil furnace to a geothermal pump, and with that, I removed all the radiators and changed to floor heating, because the energy consultant said it was more energy efficient. Exactly now, I am adding solar panels to the system.

I have dug out and insulated the floors and the ceiling, but the outer walls are still only barely insulated and only some windows are double-pane.

I am saving a huge amount of money. It is literally life-changing, to the extent I can go down in work-time. But it is not warm even when I turn up all the dials. I have a fireplace which I light up for cosy comfort, and when the house is full of guests it is completely comfortable. But I am buying an extra wood-oven for more direct heat during winter because I have plenty of fire-wood and I can make life cosier without effort.

During winter, the mean temperature is 19.5 degrees celcius. It goes both up and down, but it is fairly reliable. The way the house is built, it never gets too warm during summer, yeah.

I think I could save even more by changing all the windows. I don't think insulating the walls more than they are would change much. A consultant warned me against making the house too air tight, because the ventilation during summer is so efficient.

When the effect of the solar panels sets in, it will become cheap enough that I only need to work a few hours a week. Something to think about.
posted by mumimor at 3:28 PM on March 9, 2016 [1 favorite]

My apartment in Amsterdam had radiant heat in the upstairs floor. We put in stone tiles. To me, the tiles were perfect-- warm in the winter and cool in the summer. I loved it. However, the apartment was new, well insulated and with double glass windows. Also note that Amsterdam doesn't get as cold as parts of the US, so YMMV.
posted by frumiousb at 3:41 PM on March 9, 2016

About cooling - the way this house was built, 150 or more years ago, they thought of how to cool the house. But in-between, different owners had broken the system. So when we worked on the energy optimization, we went back to some of the old ideas and recreated some walls and doors that had been removed and opened some windows that had been been closed. The basic principle of this is based on local climate conditions - here the wind is almost aways from the west, and the house is built to close it off during winter and use it for cooling during summer. An eastern wind is the devil and nothing opens up in that direction. Etc.
The tile floors serve a special purpose here - during summer, I can regulate them to be cool and spread cool air, and during winter, I can do the opposite, all because of the properties of tiles. The wooden floors are more generally temperate, and that works well where they are.

We have both tile and wood floors with radiant heating and it is all lovely. Our dog loves it the most.
posted by mumimor at 3:49 PM on March 9, 2016

I've spent time in a finished basement with heated floors, and, in a basement, it is basement-changing. Wonderful stuff. Not sure about how it would work for other parts of a house, though. The floor was tiled and fine to walk on in bare feet.
posted by kmennie at 4:17 PM on March 9, 2016

My best friend lived for a few years in a home with radiant heat and tile floors. I get cold easily and I was not cold at all and I loved it. He was in a beach city in Southern California, where it can be chilly in the winter but no snow ever.
posted by janey47 at 4:21 PM on March 9, 2016

We have a 400 sq ft house with electric radiant floor heating. (So no cooling.) We chose electric because it's relatively cheap, since we could install it ourselves. And our space is small enough that it made sense.

Flooring - We put engineered wood floors over it, and so far, it's worked fine. The wires are buried in self leveling concrete anyway, and that's what holds a lot of the heat. I like my house warm, and that has not been a problem (but read more below).

Temperature control - This one is tricky. For our system at least, the thermostats have sensors only for the floor temperature, not for the room temperature. Because it takes so long to heat, an air thermometer would not be very useful anyway. We set our floor temperature at a constant 85 when it's cold (in Seattle, so it doesn't really get THAT cold, and I think that's the max recommended for our flooring) and 80 when it's only somewhat cold.

My goal in getting radiant floor heating was to walk on it barefoot and enjoy the warm floors, but I can tell you, the floor does not get warm. The body needs something above 85 degrees to feel warm. But our house is so well insulated that the house would be too hot if we kept the floor at that temperature.

That said, I really like it now. Here are the things I like:

* It's really stable and even. I don't have to fuss with it. My house is warm when I enter it from outside, but it's never really that hot. It's not really noticeable unless you're paying attention, but it makes the space comfortable.
* It seems really energy efficient. I don't actually know this is true. But I have solar panels, so basically electricity is "free".
* It's silent. I don't know if this is true for hydroponic systems, but my system is silent. If you care about ambient noise--which I do--then this is a godsend.

Caveat: We do also have a mini-split heat pump, which is extremely efficient in our temperate climate. It is nice to have a secondary system in place because replacing/fixing a radiant floor system can be expensive and time consuming. Also, it's nice to have something that can change the temperature quickly, especially when we were still figuring out how to set the radiant floor temperature.
posted by ethidda at 4:24 PM on March 9, 2016

I've got open loop, hydronic radiant floors in my well insulated 24x28 shop in Kamloops (similar temperatures but much dryer). It's brilliant. No drafts, no noise (you can barely hear the pump when you are standing next to it in the mechanical room, the burner on the gas water heater is louder), nice warm floor so you feel warmer (a lot of how comfortable a person feels in a room depends on the surface temperatures around them and radiant floors greatly increases floor temperatures). However it is not uncomfortably hot on your feet, at most it's the warm feeling you get when stepping where a dog has been sleeping.

My floor is a slab on grade. It has the drawbacks you mention (things break easier, somewhat harder on feet). I have anti fatigue mats in front of my bench and where I happen to stand for long periods (in front of my saw etc.) so a few throw rugs would be ok (like in front of your sink). The smooth concrete is pretty much impervious to any sort of regular household wear and tear. And if you wanted you could stain and seal, epoxy or paint the floor without issue.

any portmanteau in a storm: "Second, how effective is it at keeping the house cool? We're in Toronto so in the summer we get highs in the low to mid 30s (around 90-95F). Will radiant cooling and open windows/fans be able to keep up or would we need separate air conditioning units as well?"

You'll need separate units. Even if you wanted to pay to chill your loop, physics means you can't drop the floor below the dew point without ending up with puddles. In Toronto a lot of the cooling effect of A/C is because of the drop in humidity. 20 gallons a day wouldn't be unusual for a house that size. You wouldn't want that accumulating on your floor.

I run my sprinkler water through my floor in the summer (this is the advantage of the open loop) and it drops the floor a degree or two but not really enough to significantly cool the space. I keep using it though because it warms up the water for the plants.

Miko: "It was actually an unusual house. It was an older (1920s) house that was sort of an architectural landmark, made of poured reinforced concrete, so very insulating. "

Concrete is a very poor insulator (with the exception of aluminum window frames it's pretty much the worst insulating material we commonly build with). Some concrete homes have high insulation values but that is because they use 5" of foam as leave in place forms for the concrete. It is the foam that gives high R values.

TL;DR: I wouldn't build a house with anything else.
posted by Mitheral at 4:53 PM on March 9, 2016 [5 favorites]

For a few years I lived in a new construction triplex in San Francisco that had a lot of large windows of questionable insulation. Also, radiant heating! The floors were either thin carpeting, tile in the bathrooms, or engineered wood (I guess). There was a thermostat per floor in the home. I definitely had to set the bottom one warmer to be comfortable down low, while the top one did not need to be on much. I wondered if this might have been combated somewhat by forced air (or even ceiling fans), but suspect it was simply a three-story problem.

The floors were pleasantly warm when the system was on (stepping out of the shower was delightful). The only real weirdness was that my laundry (in a hamper on the floor) always was... disturbingly warm. I would recommend bed frames with legs over a mattress directly on the floor, etc. Other than that, it was nice (note that San Francisco hardly ever gets colder than 40 and there was no cooling).
posted by Phredward at 5:37 PM on March 9, 2016

I lived for six years in a second floor apartment that had floor heat. It was the best thing ever. We only had a simple vinyl tile floor which was quite warm. The landlord told me that the system was very inexpensive to operate to the extent that he kept it on the lowest setting possible at all times.
posted by lester at 5:39 PM on March 9, 2016

We had radiant floor heating in the house we lived in when I was a child and I have fond memories of lying on the warm kitchen floor with my sister on cold winter mornings. I would love to have heat like that again! We had carpet and vinyl flooring. This was in Massachusetts; no cooling system.
posted by mskyle at 5:41 PM on March 9, 2016

I have electric heated tile in the bathroom (San Francisco.) It's absolutely perfect in a small room where one often has bare feet. The thermostat is on a timer and it goes on before we wake up in the morning. I love it, although not nearly as much as the cats love it.

I'd be interested in putting it in other rooms, but they all have wooden floors and I'm not sure I want to get rid of the wooden floors for it. I am not sure it'd be sufficient for heating the whole house here, because drafty, but I highly recommend it as a component of your system.
posted by gingerbeer at 5:51 PM on March 9, 2016

I have electric radiant under tile in my bathroom, in a very cold climate. I utterly adore it. However, I'm not relying on it to heat the air--I also have a propane "wood" stove for that. But the feeling of comfort on your feet is that from burying your feet in warm sand. It's wonderful.
posted by HotToddy at 6:18 PM on March 9, 2016

I'll note here so that one is comparing apples to apples: The common electric bathroom tile in floor heat can't really compare to a radiant heating system. They make the tile warm but there isn't nearly enough power dissipated to heat the room.
posted by Mitheral at 7:30 PM on March 9, 2016 [1 favorite]

I had a place in Korea that used hot water pipes under the floor to heat the whole apartment. It was amazing and beautiful. It didn't cost me any more to heat the place than any other place I've lived, and it was quite effective - even if you weren't sitting on the floor, the apartment was still reasonably warm (except the bathroom, which had none, and was like going outside, but that was never really a very big deal.)

I don't get why the rest of the world doesn't do this, honestly.
posted by gloriouslyincandescent at 7:38 PM on March 9, 2016 [1 favorite]

If you put those in your basement make sure to have sufficient isolation between the heating part and the foundation otherwise you'll be paying to heat concrete.
posted by coust at 8:52 PM on March 9, 2016

I have radiant heated floors throughout most of my three-story house in the Seattle area, under wood (processed bamboo), tile, and carpet flooring. It's the only heat we use in the winter and we leave it on 24/7. Definitely cheaper than forced air, especially because ours is controlled room-by-room so we can just shut it off to guest rooms if nobody's in them. Our house was built with it in 2006; we didn't build the house but the radiant heat was a major selling point because it's so pleasant (so if you're concerned about whether this is worth the investment from a resale value perspective, it was a big selling point for us as we first saw the house in March and it was chilly, and the warm floors felt sooo nice). Our house has modern windows and great insulation and I assure you it really does get warm. We love that the air doesn't get as dry as it did with forced air, so we only use humidifiers when we're actually feeling sick instead of needing them on all the time to prevent sore throats from the dry furnace air. I am someone whose feet get really, really cold generally and I didn't wear slippers all winter, just socks. I actually look forward to stepping out of the shower onto the warm tile floor. And as someone else pointed out, it is absolutely silent.

The heat is not uniformly distributed over the full surface of the floor, but you can always find a toasty spot to stand in, and the heated air rises to warm the rest of the room. I think once in autumn we hadn't turned it on yet and we came home to an unpleasantly cold house, and that was sort of a drag because it does take a while to heat up. Luckily we also have a fireplace so we just lit a fire and sat around it for an hour or so until the rest of the house caught up.

We don't have cooling...seems like condensation would be a big problem? We have a mini-split a/c unit upstairs near the bedrooms to keep them cool in the summer, and a window unit for the bedroom that is too far from the mini-split to get cool enough. I'd say the one drawback of the radiant heat is that we couldn't piggyback a whole-house a/c onto the existing registers the way you can for a forced-air furnace.
posted by town of cats at 9:25 PM on March 9, 2016 [1 favorite]

My former workplace had radiant floor heating, and it was a PITA. The building was pretty well insulated by Australian standards, but... that was Australian standards, which are not high. It did have double glazing, but not triple, and people opened and shut doors a lot.

My main issue with it was that it took a long time for changes in the thermostat temperature to make an apparent difference to the air temperature, so if the day ended up being unexpectedly warmer than usual, you had to open windows to let all the heat out, which didn't seem so efficient, and if it was unexpectedly colder, you shivered for hours until the thermostat change seemed to make a difference. It could also be that the system was just not very good, though.
posted by lollusc at 9:38 PM on March 9, 2016

A well setup system shouldn't over and under shoot like that. Especially the modern stuff has floor, indoor and outdoor temperature sensors and will compensate for unusual temperature trends.

A hydronic system isn't suitable for setback use. Generally you want to set the thermostat at whatever your desired temperature and just leave it there. I know this can be problematic. My spouse likes to blast the heat when she is cold (even thought the air temperature is at the set point) and that isn't something you want to do with radiant heat systems.

Wild swings can also be caused by burying the tubes too deep in the floor. So an installation screw up will reduce the evenness of the heat.

town of cats: "The heat is not uniformly distributed over the full surface of the floor, but you can always find a toasty spot to stand in, and the heated air rises to warm the rest of the room."

A good installation should be fairly uniform except where intentionally not. For example in my installation the tubes are closer together in front of the man door and the 10' slider (because those are the big heat loss areas in my shop). They are much closer together in the barrier free washroom/shower so the tile is warmer where one is naked. Sometimes the installer has no choice though and ends up squeezing tube runs together. EG: to fit multiple runs though a door way or maybe the concrete is thinner to fit over a pipe or something.
posted by Mitheral at 10:34 PM on March 9, 2016

I live in Chicago and have radiant heat on the lower level of my place (which is set halfway underground). It is a closed loop water system with a dedicated water heater for the system. The flooring is tile.

It is great in the winter, it stays nice and toasty. In the summer I turn the system off and the tiles are nice and cool to the touch.

No problems at all walking around with naked feet.
posted by osi at 6:48 AM on March 10, 2016

I'm unlikely to install it in a house I own because every place I've experienced the time period of heat up and cool down has been a deal breaker. When I want it warmer or cooler, I want it now, not 3-4 hours from now. I don't think it's a good fit in my climate of highly variable temps.
posted by dancing leaves at 11:54 AM on March 10, 2016

My friends have radiant floor heating under their wood floors. It is always cold in their house in the winter. They said it just takes so long for the floors to heat up and then the house to heat up that they just leave the thermostat at something like 60F to keep it from getting too cold, but it never gets warm. Lots of blankets and sweaters.
posted by MonsieurBon at 4:06 PM on March 10, 2016

We have one house that we remodeled. 915SF 2x4 foam insulated walls, loose fill fibreglass in ceiling, fibreglass batts in floor. Mostly new windows but a couple old double hung wood widows that leak a bit. This is in Portland OR which is a gentle climate. The heating system is an open loop radiant system with a condensing gas tank water heater. There are something like 4 loops and it is only one zone meaning one circulator pump and 1 thermostat (no floor temp or outside air temp or anything like that, pretty basic.) I designed the system myself and varied tube spacing etc. based on heat loss calculations and furniture probabilities etc. The tubing is in routed grooves in plywood, in some areas covered with an aluminum sheet, and the flooring is the laminate type with a thin foam underlayment. In the bathroom the tubing is incased in a concrete substrate covered in tile. I liked it but I don't live there. The tennants seem happy but they keep the thermostat up at 71 so I'm not sure they really get the benefit. The reason I liked it was that with the thermostat down at 62 it still felt comfortable which is what I perceive as the main benefit of and potential energy savings of radiant. I have heard anecdotal criticism of radiant heated houses feeling cold but I always assumed that was because they were poorly designed.

Your question regarding wood vs tile goes to the heart of the system. Wood is poor conductor in contrast to tile. The heating system works by transfering heat from the water in the tubing to the floor at a sufficiently high rate that the floor is warm enough to radiate enough heat that it is sensible by the occupants. A wood floor or carpeting will make this harder to do, it will require the water in the tubes to be at a higher temperature in order to transfer heat at the same rate as with a tile floor. Also the temperature of the floor will be less even, hotter immediately adjacent to the tubing, cooler elsewhere. The experience of the designer and contractor are critical.

As far as cooling goes I am unfamiliar with using hydronic floors as a cooling system. With the system I installed, the domestic water for the house goes through the floor tubing before getting to the cold side of the Hot water heater so it might confer some un appreciated benefit. Open loop systems like mine might not be allowed in your jurisdiction and I'm not sure that I would want them for a larger house anyway.

As a general note I prefer hotwater heat systems,(hot water radiators or convective baseboards,) to forced air because I don't like the noise the dust and the cycling of the furnace. You can use a mix of heat emitters with a hotwater system, (add hot water convectors to heat the air in places,) but they operate a different temperatures and so require more complexity to the system.
posted by Pembquist at 1:44 PM on March 11, 2016

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