Hydronic Infloor Heating - Heat Source Location

[BBdude]

Hi All - Have a house w/ hydronic infloor heating in the master bathroom. I've personally never had infloor heating of any type.

The heat source / 7-gallon water heater is located in an unheated/unfinished attic area. Home location is in Buffalo so it does get pretty cold (winter averages in the teens). I don't see any obvious heated space where it could be easily relocated.

I've read many folks add antifreeze to the lines to prevent freezing, but wanted to solicit other views on how to remedy the issue. Previous owner seemed to have a space heater set up, but I imagine running it was $$$$.

 

[Dana]

Hi All - Have a house w/ hydronic infloor heating in the master bathroom. I've personally never had infloor heating of any type.

The heat source / 7-gallon water heater is located in an unheated/unfinished attic area. Home location is in Buffalo so it does get pretty cold (winter averages in the teens). I don't see any obvious heated space where it could be easily relocated.

I've read many folks add antifreeze to the lines to prevent freezing, but wanted to solicit other views on how to remedy the issue. Previous owner seemed to have a space heater set up, but I imagine running it was $$$$.

Is it an electric water heater? (Probably yes, given the size.)

If yes, it won't save any money on operating cost relative to an electric space heater- if anything the distribution losses of running the tubing in an unconditioned attic means it will cost MORE to run than an electric space heater. Best-case it's a crummy hack of a hydronic heating system. Using a water heater solely for space heating may even be a code violation. (It would be a code violation where I live.) Do something different.

Even if it were a gas water heater the standby losses from the extremely low load (and low duty cycle) means the operating efficiency would be terrible, possibly costing more than an electric space heater.

How important is it to have the warm floor?

What is heating the domestic hot water for the bathroom?

The heating loads of most bathrooms are pretty small, unless it's on the corner of the house and has an unusually large (for a bathroom) amount of window area. An electric towel rack of the correct wattage to cover the design heat load can be an attractive option if you don't need warm floors.

If a warm floor is a priority, tapping into the domestic hot water to the bath to run hydronic floor using a standard potable-compatible recirculation pump commonly used to always have hot water at the taps could work too, running the pump off a wall thermostat. In most locations code allows using potable water in heating systems if the lengths of heating plumbing are less than some defined amount. (I'd have to look it up to see those particulars in your area.) Often there would be a required minimum duty cycle even when there is no heating load (like in July) to avoid stagnation contamination issues, but those are easy to deal with with a recirculation system too. You'd have to measure up how much tubing you have in the floor and check that against code limits.

How is the rest of the house heated? (Ducted hot air? Hot water baseboards? Spent nuclear fuel rods in a pool in the basement? )

 

[Sponsor]

 

[BBdude]

Is it an electric water heater? (Probably yes, given the size.)

If yes, it won't save any money on operating cost relative to an electric space heater- if anything the distribution losses of running the tubing in an unconditioned attic means it will cost MORE to run than an electric space heater. Best-case it's a crummy hack of a hydronic heating system. Using a water heater solely for space heating may even be a code violation. (It would be a code violation where I live.) Do something different.

Sorry if I wasn't clear in my original post, but the previous owner was using an electric space heater to prevent the electric water heater from freezing.

How important is it to have the warm floor?

I haven't lived through winter in this house so no idea how cold the floor gets, but if this whole contraption is an expensive futility I might just disconnect it all.

What is heating the domestic hot water for the bathroom?

Gas water heater in the basement (two floors down).

The heating loads of most bathrooms are pretty small, unless it's on the corner of the house and has an unusually large (for a bathroom) amount of window area. An electric towel rack of the correct wattage to cover the design heat load can be an attractive option if you don't need warm floors.

I'm confident the dual zone heating system in the house keeps the bathroom warm. Maybe the previous owners had sensitive feet? Who knows. Heated floors is popular up here.

If a warm floor is a priority, tapping into the domestic hot water to the bath to run hydronic floor using a standard potable-compatible recirculation pump commonly used to always have hot water at the taps could work too, running the pump off a wall thermostat. In most locations code allows using potable water in heating systems if the lengths of heating plumbing are less than some defined amount. (I'd have to look it up to see those particulars in your area.) Often there would be a required minimum duty cycle even when there is no heating load (like in July) to avoid stagnation contamination issues, but those are easy to deal with with a recirculation system too. You'd have to measure up how much tubing you have in the floor and check that against code limits.

How is the rest of the house heated? (Ducted hot air? Hot water baseboards? Spent nuclear fuel rods in a pool in the basement? )

Dual zone gas furnace

Right now my biggest concern is the electric water heater (or the connected tubs) freezing and / or leaking and causing damage to the house.

 

[Dana]

Sorry if I wasn't clear in my original post, but the previous owner was using an electric space heater to prevent the electric water heater from freezing.

That's an even worse efficiency disaster (by orders of magnitude) than I was thinking! The entire kludge is probably a code violation, a potentially serious flood risk (which seems your primary concern), and possibly a fire risk too. Get rid of it!

I haven't lived through winter in this house so no idea how cold the floor gets, but if this whole contraption is an expensive futility I might just disconnect it all.

That sounds like the right plan. Take the space heater and water heater completely out, remove any plumbing that penetrates above the ceiling into the insulation, then seal the holes with appropriate materials (like can foam, etc.) It may be easier to leave the wiring in place, terminating it inside a blank electrical box, but trace the wiring back and make it's air-sealed where it crosses into conditioned space too.

Holes between conditioned space and the attic leak a disproportionate amount of air during the winter (due to "stack effect"), and often lead to wet insulation and wet wood near the leak point during cold weather. There is no such thing as an attic floor that is too air tight.

Gas water heater in the basement (two floors down).

I'm confident the dual zone heating system in the house keeps the bathroom warm. Maybe the previous owners had sensitive feet? Who knows. Heated floors is popular up here.

With the water heater two floors away recirculation system might be desirable whether it's heating the floor or not, independently of the space heating option. But if the floor heat is On retrofits it's common to use the cold supply plumbing for recirculation systems but tepid or hot water coming out the tap is likely to happen if using the cold supply as a heating return, so a dedicated return, teeing in close to the cold-inlet to the water heater would be preferable. Since it's not really needed as primary heat for the space a floor thermostat would be preferable to a wall thermostat, to avoid overheating the space.

Dual zone gas furnace

...and not a hydronic boiler, which is why they hacked in a kludgey water-heater hazard non-solution.

Electric mesh floor heat under the flooring where the warm floor was most desired would have been more appropriate, better controlled, and probably cheaper too, even if it meant replacing some flooring.

 

[Fitter30]

Sorry i disagree their is nothing like radiate heat. Quiet and nothing like stepping on a warm floor. As for a water heater for a boiler their no problem using one. My father used one for over 30 years to heat a basement with fintube. Guess how much water in the system 30% propylene glycol good to go. Worried about a leak put a safety water heater pan under it piped outside. Unlesś i missed something.

 

[BBdude]

Hi Both - Thank you for the input and feedback. Really helpful!

@fitter30 - How can I tell if the previous owners included 30% propylene glycol? Is it something that should be regularly replenished or one and done?

 

[Dana]

Sorry i disagree their is nothing like radiate heat. Quiet and nothing like stepping on a warm floor.

I don't think we really disagree here.

As for a water heater for a boiler their no problem using one. My father used one for over 30 years to heat a basement with fintube. Guess how much water in the system 30% propylene glycol good to go. Worried about a leak put a safety water heater pan under it piped outside. Unlesś i missed something.

There is nothing wrong with radiant heat, but using a water heater solely for space heating is barred by code in a number of states. I'd have to look up NY code, but it would be a violation in Massachusetts or Connecticut, possibly nullifying any insurance claims for water damage or fire if things go awry.

And what could go wrong? Given what little we know about it I suspect it lacks even the basic necessities of a hydronic heating system. Is there even an expansion tank on that tiny isolated hydronic system to keep from over pressurizing the water heater? Is there an adequate drain in place for the T & P valve? Sticking a pan under it for leak protection won't protect the pan and/or it's drain from freezing up during normal mid-winter coolth in Buffalo NY. A slow drip can easily turn into a block of ice in a vented attic over the course of a week. An ice plug can form in the drain in less than a day.

FWIW I'm located in Massachusetts, using a (tankless) water heater as a boiler. But since I'm also using it for domestic hot water (isolated by a heat exchanger) it still passes muster from a code compliance perspective.

But sticking the water heater in a vented attic above the insulation in a location with a 99th percentile temperature bin of about +7F then heating the attic with a space heater to keep the plumbing from freezing is sheer lunacy. Electric mesh heating on or under the sub floor has none of the risks, and uses a LOT less electricity to achieve the same barefoot comfort than the current system. Using the main water heater in the basement to heat that tiny zone would be fine- but whether it's "worth it" to reconfigure the system to do it that way is up to bbdude. But getting rid of the hack really IS worth it, on several levels.

 

[BBdude]

And what could go wrong? Given what little we know about it I suspect it lacks even the basic necessities of a hydronic heating system. Is there even an expansion tank on that tiny isolated hydronic system to keep from over pressurizing the water heater? Is there an adequate drain in place for the T & P valve? Sticking a pan under it for leak protection won't protect the pan and/or it's drain from freezing up during normal mid-winter coolth in Buffalo NY. A slow drip can easily turn into a block of ice in a vented attic over the course of a week. An ice plug can form in the drain in less than a day.

I'm not handy, but can share what I know ...

• There is an expansion tank on the water heater for the hydronic system.
• There is a drain / pan, but obviously nothing preventing slow leaks from freezing.
• The water heater isn't in the attic. Hard to explain. It's on the backside of the bathroom wall in an unfinished space above the garage. I can access the space through a door in my bedroom. Guessing some of the heat from my bedroom does flow into this space, but would still be quite cold. We might finish the space, but that's down the road a bit.

But sticking the water heater in a vented attic above the insulation in a location with a 99th percentile temperature bin of about +7F then heating the attic with a space heater to keep the plumbing from freezing is sheer lunacy. Electric mesh heating on or under the sub floor has none of the risks, and uses a LOT less electricity to achieve the same barefoot comfort than the current system. Using the main water heater in the basement to heat that tiny zone would be fine- but whether it's "worth it" to reconfigure the system to do it that way is up to bbdude. But getting rid of the hack really IS worth it, on several levels.

I asked my home inspector about the setup, but he was pretty useless.

I will definitely not use a space heater. I don't really care to use them for anything .

Electric mesh would have been the wise choice, but my guess was this hydronic system was cheaper to install (even if potentially more expensive to run). I'm not entirely sure why they didn't just run a line from the basement, or off the existing lines to to the bathroom, to heat the floor? Bathroom looks like it was a full gut so doesn't make sense to me (then again I'm not handy!).

 

[Reach4]

Sorry i disagree their is nothing like radiate heat. Quiet and nothing like stepping on a warm floor. As for a water heater for a boiler their no problem using one.

How about heating wires in the floor. If the hydronic heating uses heat pump, that would be more power-efficient.

Or if freezing is a concern, the electric WH is not going to freeze when turned way down but not off. The pipes could freeze, but those could get pipe heater cables to prevent the pipes from freezing.

 

[Dana]

I'm not handy, but can share what I know ...

• There is an expansion tank on the water heater for the hydronic system.
• There is a drain / pan, but obviously nothing preventing slow leaks from freezing.
• The water heater isn't in the attic. Hard to explain. It's on the backside of the bathroom wall in an unfinished space above the garage. I can access the space through a door in my bedroom. Guessing some of the heat from my bedroom does flow into this space, but would still be quite cold. We might finish the space, but that's down the road a bit.

So it's in the garage's attic, with an insulated wall between the heated space and the garage's attic or perhaps unfinished "bonus room"?

If it was built out as a bonus room, are the walls floor & ceiling of that space currently insulated?

If currently uninsulated, could the walls/floor/ceiling of the bonus room space be insulated? There may even be NYSERDA subsidy money for insulating that space, even if you're not immediately going to turn that space into finished living space, or use it as walk-in closet.

If you were handy you COULD just build an insulated mechanicals closet/cabinet around the system in the space, and remove insulation from from the section of bathroom wall & mechanicals closet, which brings the entire system entirely within the air pressure & thermal boundary of the house (where it belongs.)

The insulated mechanicals closet approach doesn't fix any potential code or insurance nullification issues, but it fixes the freeze-up risk and the serious heat loss of needing to run a space heater to heat an uninsulated room. Ideally the entire space above the garage (not just a tiny mechanicals closet) would be air tight and insulated between the outdoors and the garage below. Even if not actively heated with extensions to the duct system the freeze up risk drops to effectively zero.