Radiant Floor Heating

By Tim Carter
©1993-2009 Tim Carter

Summary: Radiant floor heating is heavenly and perhaps the most comfortable heating. Installing electric radiant floor heating is not a do-it-yourself project. Find a seasoned installer who can handle radiant in floor heating and all the design specifications and piping.

DEAR TIM: I have a unique opportunity to convert to radiant floor heating in my home. A complete renovation is in progress, and I'm convinced radiant floor heat will be the best for me. Is installing radiant floor heat a task that the average homeowner can do successfully? What do I need to know to ensure my radiant floor heat system is installed correctly? Is one radiant floor heater better than the other? Victoria B., Holderness, NH

DEAR VICTORIA: Radiant floor heating is heavenly. If you've never had it before, you'll not sacrifice it in any future homes. The house I'm living in now is the first one I've ever had that has radiant floor heat. I've known for years that it's perhaps the most comfortable, but never experiencing it, I couldn't stand witness. Well now I can. I'm smitten with it.

These radiant-floor-heating pipes go into the concrete slab and keep it toasty warm. PHOTO CREDIT:  Tim Carter
These radiant-floor-heating pipes go into the concrete slab and keep it toasty warm. PHOTO CREDIT: Tim Carter
Hot water radiant floor heat is an amazing system, whether the flooring system is wood or masonry. The floor itself, once heated, sends out low-level infrared rays through the air to heat your body and any other solid object in the room. No heat is wasted in the air. Forced-air heating systems don't really do that. The water vapor in the air is warmed, and as these microscopic molecules are blown through the air they inefficiently transmit their warmth to you as the warm air hits you. It's just not the same feeling.

You can forget about installing radiant floor heat yourself. It's an extremely complex task requiring enormous skill and talent. You want a seasoned installer that can prove to you he's installed countless systems. The calculations, flow rates, Btu heat-loss calculations and engineering required to get a residential system to work flawlessly are difficult. Installing the actual equipment and piping is another skill set entirely. Focus your energies on interviewing several pros, talk to past customers and decide which pro will do the best job for you. Going with the low bid in this situation could be an enormous mistake.

Radiant floor heat starts its life in a boiler. Modern radiant-floor heaters, or boilers, are highly efficient, and they are amazingly compact. You will be stunned at how small yours will probably be. Don't restrict your budget here. You want a superb boiler, so ask the different installers who makes the best one and why they feel that way. Invest time in searching for reviews on the Internet.

Water is heated in the boiler and sent into a piping system that recirculates this water through any number of interconnected loops. One of the magical things you can have with radiant floor heating are individual zones. My current house has seven separate zones, each one controlled by its own thermostat. I can control the heat level in each zone. A zone typically is a grouping of two or three rooms that are almost always connected to one anther. For example, in my basement, a bedroom, large closet and a bathroom are on one zone. The other four rooms in the basement are on another zone.

The water is pumped to each zone by separate recirculating pumps. These workhorses are one of the few moving parts in a common radiant-floor-heating system. High-quality recirculating water pumps can last many years.

To make sure your radiant-floor-heating system is installed correctly, you need to ask lots of questions as you interview installers. Talk to them about the necessary calculations as to how they know there will be enough heat on the coldest possible winter days. Discuss which plastic radiant-heat piping will provide years of service. Ask about how the piping will be protected so it will never get punctured. Inquire about insulating concrete slabs so you don't bleed heat to the outdoors. Many radiant-floor-heat boiler manufacturers have some good tips as well at their websites.

Make sure that all the promises made by your installer are put in writing in the contract. Take many photos of each step of the installation, especially those parts of the piping that will be covered and never seen again. Inspect the work to the best of your ability as you take the photos. Make sure your installer gets a permit and that the inspector gives the job her/his seal of approval.

One of the superb characteristics about radiant floor heating is the warmth of the floor. You can lay on the floor and be amazingly comfortable. Other floors are cold or uncomfortable. A floor that's heated is a dream to walk on with bare feet or just in socks. You'll not believe it until you try it.

Concrete slabs that contain the radiant-floor-heat piping become massive radiators. Once the concrete gets heated, the thermal mass radiates the heat into the room for hours. You can get the slab up to temperature and then turn back the thermostat. I've actually had my basement floor radiate bone-warming heat for up to 12 hours after the thermostat was turned back.



Comments:

Laura
21 Dec 2008, 18:26
Hi - could you tell me what the annual maintenance (if any) has to be done on a radiant floor system?
Thanks!
Steve Newcomer
21 Dec 2008, 18:37
Is there a way to install radiant floor heat on an existing concrete slab? I am installing a tile floor in my family room that is the core of our two story home. My existing heat is gas FWA I am trying to determine if this is feasible before the tile is installed rather than regret that I didnt do it when I could. This would be supplemental heat and provide additional comfort in the family room and adjoining kitchen.

Thank you very much for your feedback.

Steve
Mark
22 Dec 2008, 09:03
I am a homeowner in Cincinnati with radiant heat - radiators in the older section of the house and radiant floor heat in the additions.

Maintenance is very simple. I bleed any air on the radiators and clean (vacuum) the boiler before I light the pilot light and throw the electical switch. The circulators are sealed and do not have to be lubricated. That's it!

Existing slab installation - can be done. I have installed radiant floor heat on my second and third floor bathroom floors (master shower walls, too). That was easy compared to what you have with the concrete slab, however. Your big concern is the heat sink of the concrete slab 'sucking' all of the heat from the tubes. How are you going to insulate the floor? I think your only choice would be to build a 'false' floor over the concrete floor and use a foam insulation between studs on the flat. (This is what I did in my family room, converted from a sunporch, over an unheated garage.) You would then build up from there. This is going to steal head room however.

I used a dry system to install the tubing in my second and third floor baths. I made my own based upon the Watts SubRay system. This added 3/4" to the floor thickness plus 1/2" for the concrete board. By adding another 3/4", you could use a poured concrete over your insulation. This would give a more even heat.

If you can afford the head room loss, you will love the warm floors!

Good Luck,

Mark
rebel
09 Jan 2009, 06:52
Bob says that this is not a do it yourself project.In my area it means getting robbed. Having a contactor do this is out of the question,because I can't even get one to do ductwork around here.
Mike
02 Apr 2009, 19:14
Looking at installing hydronic radiant heat in new contructions. Any thoughts on the best way to do this. I have some contractors pitching either Warmboard or QuikTrak which sits on top of the floor or CLimate Panel that sits under the floor in the joists. Any help would be appreciated. thanks

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