I am in the process of turning a bedroom into a master bath. My home is heated via hot water baseboard. Originally I had planned to install an electric heat mat under the tile to warm the floor but a plumber friend suggested using the copper fin tubing (the type used in the baseboards) but run a couple lengths between the 2X10s under the sub floor to heat the bathroom floor. Has anyone tried this approach? Thanks in advance, Bill
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You might be happier with the electric heat under tile, and a programmable thermostat. Wonderful comfort, even in warm months. In-floor heat fired by a boiler won't give you that kind of seasonal (or even day-to-day or hour-by-hour) flexibility.
I am presuming the room is heated adequately now, with the hot water baseboard units.
I beg to differ. Infloor supplied by a condensing,modulating boiler with the proper controls would work just fine.
Electric mats will probably be cheaper.
And the fin tube in the joist space is iffy at best.
Unless the ceiling under the new bath space is presently unfinished or already "open", there will be the additional, and likely not insubstantial, monetary and disturbance costs associated with removal and making good of interior finishes.
As you likely will not want a floor temperature in excess of 90 F, and as your boiler water temperature can, at times, push 180 F, you'll need a separately zoned/controlled/mixed- for-temperature heating circuit. This all adds up to big dollars and complexity of installation.
I agree with your using an underfloor electric resistance mat, readilly available as an off-the-shelf item and easy to install. These are usually 110 V, and the thermostatic control is included with the mat kit. There is not likely a less complicated system for a retrofit, as is your situation. Go for it!
I've done this a lot in smaller baths and kitchens with tile floors and even have it in one of my own baths.
I run tubing in every joist bay. Use a by-pass valve to throttle it.
Please describe what you mean as a "by-pass valve".
I once put in a toe-kick forced air heater (really just a heat-exchanger with a fan, works off of a hot water system. The heater loop came off of an existing loop. I used a very unusal 3/4'' tee, it had a little copper "arm'' on the inside that directed most of the water flow in one direction, thereby most of the hot water by-passed the toe kick heater. I have no clue if everything would have been the same using a regular tee. All I remember was the fancy tee cost over $10.
Anybody have an idea what the above is called? sorry about the hi-jack
You're talking about a venturi tee. It draws some of the flow up and through the toe-space heater. A cheaper version are little cones that you can insert in a regular tee.
By "by-pass valve", I mean a valve that I can turn to divert only part of the flow through the fin tube so as not to over heat the floor. Off the main loop I tee off to the fin tube in the joists bays. On the run, I install a ball valve then the tee returning the flow back from the fin tube. The two tees should be less distance apart than the total length of the fin tube.
Here's an illustration showing how to retrofit an existing baseboard system with a radiant floor heating system. Shown with tubes above or below depending on accessability.
View Image
For a full screen shot go here:http://www.healthyheating.com/Page%2055/Page_55_p1_schematics.htm>
Locate the link titled "Retrofit an existing baseboard system with a radiant floor heating system">
Edited 11/27/2005 5:47 pm ET by RBean
Nice-looking drawing and good solutions also, Robert!IMO, the debate of electric vs. hydronic centers simply around whether the home has a boiler or not. If there is a pre-existing boiler, methinks hooking a small radiant zone into the rest of the system makes the most sense. In homes with nary a boiler, the electric retrofit can supply comfort at an acceptable price-point.To All: Don't overlook the opportunity to run the stuff in walls either if the floor is out of the question. Plenty of BTU's can be pumped into a room that way and it may be less disruptive doing it behind a to-be-remodeled wall than ripping up joist bays.
as always Sir, you are right again...the HTC for walls is about 1.4 Btu/hr/sf *deg F. We have large radiant wall in our home. Ceilings are a nominal 1.2 Btu/hr/sf * deg F.
By the way there's a group of us about to dive into a couple of deep topics...
First is "exergy" as opposed to energy and the second is the influence of short wave radiation on surface temperatures ...are you interested in participating? It would be great to have your mind in the discussions!
Let me know via my [email protected]
RBean
web: http://www.healthyheating.com
blog: http://wonderfulwombs.typepad.com