In floor heating - water or electric?

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Old 12-26-12, 11:03 AM
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In floor heating - water or electric?

I have an old 3 storey house with a hot water radiator system. Previous owner took out the rad in the kitchen and installed baseboard heaters. Now I'm renovating and want in floor heating in the kitchen. For a small area like that should i just do electric or add on a water flooring section to my main hot water system? Any thoughts?
 
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Old 12-26-12, 11:22 AM
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As long as water doesn't involve adding a lot of equipment to your house, it would be my choice. Electric costs quite a bit to use.
 
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Old 12-26-12, 11:41 AM
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Why do want to remove the baseboard units?
 
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Old 12-26-12, 11:46 AM
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Kitchens and baths can be problematic with infloor.
Cabinets and tubs, etc, create unheated floor space that can take away from your heated area.
There is always definite possiblility that the in floor will not have enough output to heat the space. At this point you either live with a less then idea area, or some form of supplemental heat.

To add in floor to a system, you need to zones the system. You will be adding operating aquastats, mix valves, extra circulators etc. Sometimes it costs more than you would ever spend extra on electrical costs of the electric in floor.
 
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Old 12-26-12, 03:16 PM
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Have you guys seen the cost of those electric mats? Not cheap! I think installing the water could be the way to go.

As was already said, this will probably only be enough to have toasty warm floors, but not enough to heat the space. Plan on adding a toe kick heater if you don't haver wall space for radiators.
 
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Old 12-26-12, 03:22 PM
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We took out a wall so there isn't really space for the baseboard heater that was in there. I'm curious about why in-floor wouldn't heat enough to warm the space? I've heard of houses totally heated by in-floor, so I assumed it could be done. Does that apply to both electric and water?
 
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Old 12-26-12, 03:36 PM
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Mixing floor radiant heating with conventional baseboard or radiators is tricky - they often can't be supplied with the same temperature water and calculating the heat output to the room through a floor can be complicated. Of course, it is possbile to do. Best to get Siegenthaler's "Modern Hydronic Heating."
 
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Old 12-26-12, 03:46 PM
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OK thanks, I just put it on hold at the local library. I think my system would require some significant modifications to do this, but some of it is work I was considering doing anyways. Currently my system has to run the water very hot due to the bypass system in place. If I can make my system more efficient at the same time it might make all the work worth it.
 
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Old 12-26-12, 03:53 PM
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A lot depends upon HOW you want to transfer the heat from the hot water heating system to the floor. Systems that fasten tubing to the underside of the subfloor are less likely to transfer enough heat to the room than are systems that have the heating tubing on the surface of the floor. It also depends on the finish floor material. Using tubing embedded in a lightweight concrete (Gypcrete) floor and then covered with ceramic tile is an excellent way to go but it requires a substantial subfloor to hold the weight and it also requires a fair amount of work due to the thickness of the finished floor.

Using something similar to Warmboard with a laminate floor or thinner engineered flooring is also good and has a much lower added height than will a slab. Probably the worst would be to use an underfloor tubing arrangement with a carpeted finish floor.
 
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Old 12-26-12, 03:57 PM
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The floor is currently old hardwood. My plan was to rip off the hardwood, place the heating (electric of water) on top of whatever subfloor is there, and cover with ceramic tiles
 
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Old 12-26-12, 04:04 PM
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I think you can use Warmboard under ceramic tile with thinset mortar. If you can, this would be a good mix and the floor would be at about the same height as it is now. Understand that Warmboard is not cheap.

Warmboard - The Leader in Energy Efficient Radiant Heating
 
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Old 12-26-12, 04:07 PM
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You will still need to have a temperature regulating valve and second circulator pump to supply the oxygen barrier PEX tubing in the Warmboard along with the requisite thermostat and possibly switching relays.
 
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Old 12-26-12, 05:51 PM
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OK so I have an unused pair of supply and return pipes in my system. Here's an old diagram, nevermind the varying rad temperatures, vacuum breaker, and stuff, that's all fixed. https://www.dropbox.com/s/tqi6a201tc...%20diagram.jpg

On the supply side I could hook up a temperature regulating valve like this:
Cash Temperature Regulating Valve and a small circulating pump, then pex all the way through the warmboard, back in to the return? Is that the right order? Sounds fairly simple actually. What might I need switching relays for?

edit: oh yeah, how does the thermostat play into that?
 
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Old 12-26-12, 06:07 PM
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Forget those capped ends of the existing system. You really need a new heating loop starting at the boiler, right after the expansion tank. You will need a new circulating pump and a three-way temperature control valve. There is lots of information on the methods of piping a radiant loop available on the web.; essentially you want to pump the water around in a circle through the temperature regulating valve in a manner that allows only enough new boiler water to enter the radiant loop to maintain the required temperature for that loop which will be in the neighborhood of 90 to 120 degrees. The floor surface temperature should never run more than about 95 degrees or it will be too hot for comfort.

The new thermostat and switching relay will be used to control the new radiant loop's circulating pump and the boiler burner. You cannot run the radiant system from the existing thermostat, it just won't work for several reasons.
 
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Old 12-26-12, 06:27 PM
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OK, after ripping out a wall, there is now not enough room for sufficient baseboards. Can you post a sketch of the kitchen layout, with approximate dimensions? How about adding kickspace heaters under all the cabinets? Do you really want to build a new floor to accommodate heating panels that might not be satisfactory?

The first thing might be to calculate the heat loss from the kitchen - and compare it to whatever in-floor systems you consider. Typically, less than 20 Btu/hr ft^2.
 
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Old 12-26-12, 08:35 PM
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Well, I'm not a huge fan of having hardwood floor in the kitchen, and it's old so it's no real loss there. New tile would be nice. That corner of the house is drafty because when we insulated the basement they went around the electrical stuff in that corner below, so even with the kitchen toasty warm when we had the baseboard heater, I always had cold feet while washing dishes. So it's partly a comfort issue, but I do certainly want to do everything I can to make sure this solution will be heating the room properly. If absolutely necessary we could put heaters under the cabinets, I was just hoping to do this entirely with in-floor

Here's a sketchup drawing, the room is 14.5' long, and is 8.5' wide from wall to the edge of the island cabinets. So it's about 90-95 sq. ft of flooring.

https://dl.dropbox.com/u/650719/kitchen.png
 
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Old 12-26-12, 11:45 PM
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I did a rough heat loss calc, might not be the most accurate thing ever, but I came up with a requirement of 3200 btu. This is not accounting for the fact that most of the outside walls are covered by cabinets, but also not accounting for the drafty basement wall below the one corner. According to the PEX website, radiant in floor can give 22-30 btu per sq ft. I have 90sq ft to work with so I can get 2700 btu theoretically. Close enough?

If I have to supplement with a toe-kick heater anyways, then I suppose I should just go with the easier, and likely cheaper infloor heating option, electrical, since it will only be supplemental.
 
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Old 12-27-12, 12:03 AM
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It is really unlikely that you can achieve 30 BTUs per square foot. Even at 25 BTUs per square foot you are only getting about 70% of your calculated requirement and that is with an overly optimistic guesstimate of required BTUs in my opinion.

Remember this axiom concerning radiant floors: Radiant is easy to do wrong but difficult to correct after the fact.

Spend some time doing several heat loss calculations in great detail. Do your calculations as the structure exists and also with different combinations of energy saving updates. Also take into consideration just how often the temperature in your immediate geographical area actually drops to "design" temperature. If it seldom drops to design temperature then try your calculation at a more "normal" temperature to see if it will work during normal winter days. If it does you may be able to suffer the few hours or days when it gets really cold. If it doesn't calculate out then radiant is not for you.
 
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Old 12-27-12, 12:18 AM
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Thanks, I'll try to get more precise. Do you (or anyone else) happen to know what kind of figure to use for the air exchange rate, in a house that has no air exchanger?
 
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Old 12-27-12, 06:08 AM
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Warmboard wants Pex-Al-Pex tubing.
This controls the thermal expansion of the tubing while in the grooves. Keeps it quiet.
 
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Old 12-27-12, 09:27 AM
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Do you (or anyone else) happen to know what kind of figure to use for the air exchange rate, in a house that has no air exchanger?
Anything quoted over the Internet would be no better than simply picking a number at random. You really need a blower door test to ascertain the air exchange rate. Even someone standing in your house could only make a wild stab that more likely as not would be wrong by quite a large percentage.
 
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Old 12-27-12, 11:25 AM
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Hmm. How much is that gonna cost me? I had one done by the government for a retrofit grant, but then they insulated the basement and attic, so it's out of date. The figures were pretty wild too, from what I can tell.

Air leakage rate @ 50 Pa: 8.87 ACH

ACH = number of air changes per hour

Equivalent Leakage Area: 1856 cm2
 
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Old 12-27-12, 11:31 AM
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Alternately, if I were to install something like this, would it need all of the additions to my heating system, circ pump, etc?

Beacon Morris K42 Kickspace Heater Twin-Flo III, Kickspace Heaters

If I could use the capped pipes for these, that would make it a little more attractive.
 
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Old 12-27-12, 11:43 AM
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The toe space heaters are a good idea. You could use the capped fittings and then a thermostat that just controlled the fan in addition to a fan control thermostat on the water outlet of the heater. This is probably the easiest and cheapest way to add heat to your kitchen.
 
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Old 12-27-12, 12:12 PM
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The Beacon-Morris really doesn't need a wall thermostat. The built-in aquastat turns the kicker's fan on whenever there is hot water circulating through the unit. If you want to set up the kicker on a separate zone, then you would need a zone valve and a wall thermostat. I have two of those units, and my whole house is set up as one zone, so the kickers run whenever there is a heat call for the house.

The B-M units will also fit in the standard stud spacing of a wall. If you put them in the toe-space under a cabinet, you need to cut a removable hatch in the bottom of the cabinet for maintenance access. You will probably need several kickers to heat your kitchen.

B-M will provide a special low-temperature aquastat if you need them - I did.
 
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Old 12-27-12, 01:27 PM
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No, you don't HAVE to have a separate thermostat for the toe-space heaters but if they are oversized then you can keep from overheating the space by disabling the fan via the room thermostat. The thermostat attached to the heater itself (the return line) is to only allow fan operation when the heater is actually capable of putting out warmed air. Otherwise the fan would run continuously and most of the time it would be cool air and cause drafts.
 
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Old 12-27-12, 03:38 PM
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If I have to set up more than one toekick heater I think I'd lean towards electric in-floor heat instead. It's not too much more expensive and the extra comfort level is significant. I guess this is the water forum, but what are the drawbacks to going electric in-floor instead?
 
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Old 12-27-12, 04:52 PM
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Based on my experience and your preliminary heat-loss calcs, I don't think you can get by with just one kickspace heater. The primary disadvantage to electric is that it is quite a bit more expensive to run than gas, per Btu. Also, if your main electric service is borderline, say 100A or less, then it may have to be upgraded, at considerable cost, depending upon your current loads. If your main power panel doesn't have two adjacent spaces available for a new 240-V branch, then that will require some extra work to feed the electric heat.
 
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Old 01-03-13, 10:27 PM
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Having spoken with the folks at warmboard, they figure I can get 30-35 BTU per sq ft. I'm leaning towards doing that and supplementing with one toe kick heater or just having an electric radiator in there when needed. Would it be simple to run a toe kick heater off a loop set up for radiant?
 
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Old 01-04-13, 09:20 AM
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Would it be simple to run a toe kick heater off a loop set up for radiant?
You wouldn't want the toe kick on the low temperature radiant loop.

The toe kick needs supplied by the high temp boiler water.
 
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Old 01-07-13, 11:37 AM
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I've talked to a few contractors and I'm even more confused than ever. Some guys say that hydronic can be used as a primary heat source, and electric is just for comfort, while other guys say the exact opposite!

One contractor here, the guy who I've had out to service my system, told me to just go with electrical, it's cheaper. Another guy told me electrical doesn't heat enough to be used as your heat source.

Oh yeah, and the quote for plumbing a toe kick heater wasn't much less than plumbing the in floor.

I'm at a loss. I really appreciate your help.
 
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Old 01-07-13, 03:28 PM
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Some guys say that hydronic can be used as a primary heat source, and electric is just for comfort, while other guys say the exact opposite!
Seems pretty obvious that neither is camping around the right fire.

EITHER can be a primary heat source, and either can be used to warm a floor for comfort.

In the short term, hydronic radiant might be more expensive to install but far cheaper in the long term to run.

But without the entire conversation for context, we don't really know what either folks meant.
 
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Old 01-07-13, 03:47 PM
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I've talked to a few contractors and I'm even more confused than ever.
That's not all that uncommon, which is why most of us here are DIYers.
 
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