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Thread: Radiant Floor Heat
05-06-2009 02:47 PM #1
Radiant Floor Heat
I'm going to convert my 1st floor of our home to radiant floor heat. My brother did it for his kitchen/dining room, so lessons will be learned from his job.
I'm gonna start with the living room and than move on to the kitchen. Anyway, I'm looking at Above Floor/Plate System System, that will be covered with new hardwood flooring. In the basement, I will be installing installation in-between the floor joists as well. This method should be very effective heating wise. Hot water goes through the tubes and spreads out the heat to the heat plates.
Pro or cons? Anybody have radiant heat on their floors?
Here the tubing and plates are located on the top side of the floor deck. The tubing can be run in virtually any direction. The system can be adapted to several types of finish flooring, and is particularly well suited for nailed down wood floor installations.
Begin by fastening 5/8” - 3/4” plywood or oriented strand board (OSB) “sleepers” to the floor. The sleepers are placed to create 3/4” wide grooves into which the tubing and trough portion of the plates are recessed. To minimize any squeaks, the sleepers should be glued as well as nailed (or screwed) to the subflooring.
Grooves for the return bends, as well as other curved tubing paths can be formed by routering out the 3/4” plywood or OSB. Another way is to place triangular shaped spacers to support the secondary floor layer at curved areas.
The plates are set into the grooves with ends spaced about 1” apart. Pull each plate against one edge of the sleeper and tack it in place with two or three light gauge staples on the same side (and only on this side). This allows the plate to expand as the tubing is pushed into it as well as when the plate heats and cools.
Then tubing is laid out and pushed into the grooves in the plates. Stepping on the tube as it aligns with the grooves ensures it is pushed all the way into the groove.Above floor tube and plate systems are ideal when nailed-down wood flooring will be installed. The flooring can be placed directly over the tube and plates without needing an additional cover sheet. The flooring should be installed with its long dimension perpendicular to the tubing. Nails can be driven through the heat transfer plates, through the sleepers and into the subfloor. Be careful not to drive nails through the tubing on return bends or other areas when the tubing is not visible as the flooring is laid. If the tubing needs to run parallel to the flooring at times, it is best to drill a shallow hole through the subfloor and route the tubing through the floor framing where it is protected against nail punctures. The tubing can also be “plunged” beneath the subfloor and then routed up through the bottom plate of a partition to connect to the manifolds.
For other types of flooring, it is necessary to install a thin 1/4” or 3/8” cover sheet over the tube and plates to serve as a smooth stable substrate. Plywood is often used as the cover sheet under vinyl flooring or carpet. Cement board has also been used under ceramic tile. All tubing circuits should be pressure tested prior to installing the cover sheet. The tubing should remain pressurized as the cover sheet is installed. Be careful not to drive fasteners through the tubing when securing the cover sheet.
The same concept of the sleeper system can be used in low heat load installations, but without the heat transfer plates—mostly for floor warming systems.
The wood structure is a poor conductor of heat so there is limited heat transfer sideways. The relatively thin layer directly above the pipe will allow a lot more heat through than sideways. This results in large local temperature differences depending on the position of the pipe. This effect limits the amount of heat that can be transferred without creating high temperature “lines” on the floor surface.
The spacing used should be 6”-8” and again only a limited amount of heat output can be provided. To overcome this limitation, some manufacturers produce pre-routed plywood sheets with aluminum layer attached to it to improve sideways transfer.
05-06-2009 02:58 PM #2
Back in the 80's, I lived in married student housing at GT for about a year (aka "Third World Towers" ;-) until we got busted for the cat.
That building had it, from some engineering exercise from when they built it, way back when. It was just embedded water pipes running hot water through the concrete floors. Worked great. It not only works but, in my experience, you get the same comfort level with a lower thermostat setting. My totally unsubstantiated theory is that, for reasons I don't understand, perceived comfort has a whole lot to do with surface temp of walls and floor, and not just air temp, and in-floor heating somehow helps exploit whatever goes on with that.
Last edited by rshackelford; 05-06-2009 at 03:01 PM.
05-06-2009 03:37 PM #3
When I lived in Buenos Aires back in the mid-90's, in a swank high-rise apartment I might add, the building (and many in that city) made use of the same system the Shackster describes above, water pipes with wicked hot water running thru them under the wood flooring. Worked marvelously, too good in fact. The downside for me in this building was that the tenants of individual apartments had no control over the "thermostat". I remember having to run a window air-conditioner unit in the midst of winter because the floor heating system was too efficient! No doubt this "technology is drastically modernized.
05-06-2009 03:41 PM #4
05-06-2009 03:45 PM #5
05-06-2009 03:47 PM #6
The thing we weren't in control of is when they turned the boiler on and off seasonally, according to the calendar. I think maybe we got some heat we didn't ask for just from the pipes running in the walls to get to other floors, but it wasn't a big deal.
05-06-2009 09:49 PM #7
You would live in a convection oven!
Convection is why it works so well. Heat rises and naturaly flows to the areas of lower energy, the cold ones. So the heat naturally disperses itself evenly. Ceiling ducts are kind of silly for heat.
I solved my heating issue by moving to Florida. My heat was turned on exactly one time when the home inspector tested it. My solution is not ideal for most
05-07-2009 05:55 AM #8
I used to watch that PBS show Hometime. The home improvement guy and his latest GF doing home repairs. Sometimes they just did an improvement show, like build a deck, or remodel a bathroom. Sometimes they built whole houses from the ground up. Whenever they did the whole house thing, they almost always included the radiant floor heating. It's a big job, and a big expense... but it would be so nice, and add so much value to your home.
Think about it... what makes you feel cold? Walking on a cold, non-carpeted floor when you first wake up. Think how sweet it would be to walk on toasty, warm tiles first thang.
05-07-2009 06:00 AM #9
I have installed a few of these. Pretty cool stuff.
I think you will like it.
05-07-2009 08:29 AM #10