Temperature setting for radiant floor heat

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dodgy55
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Temperature setting for radiant floor heat

Post by dodgy55 »

My kitchen only had a toe-kick element under the sink cabinet as the source of heat. I found this very inadequate and after some research I opted to install radiant floor heat in my kitchen. My kitchen floor is the old fashion 3/4" oak flooring. It was a semi-DIY project. I purchased all the components online. I installed the pex tubing under the kitchen floor and had a professional plumber tie the tubing and circulating pumps into my existing natural gas boiler. I find that my floor is toasty warm but the ambient air temperature is still on the cool side. The thermostat is now set at 95 degrees. Temperature is controlled by a floor probe in the under-floor sheathing. Not sure if I need to raise thermostat setting. I am curious as to the experiences of other BHs with wooden floors heated via radiant heat.
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Daisy Dog
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Re: Temperature setting for radiant floor heat

Post by Daisy Dog »

Dodgy55,

I am currently in the process of buying a home with bamboo wood floors and the kind of radiant floor heating you have. The inspection isn't scheduled for a couple of weeks and I am totally unfamiliar with this heating system. Hopefully I'll learn what I need to know then! I would not be happy being "cold" as I am retired and in my home most of the day.

Thank you for posting this. I hope someone else can help - and when I learn something, I'll report back.

Daisy Dog
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CaliJim
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Re: Temperature setting for radiant floor heat

Post by CaliJim »

We have hot water radiant under a tile slab. on grade, floor. We use thermostats that measure room air temp, not floor temp. Works great, except my wife is warm blooded. She turns the thermostat down all the time.... and I end up cold.... but then ... that's my nature.

Most radiant systems are designed for the water running through the pipes to be set between 85-125f. Floor surface temp should be set to about 5 degrees above room air temp.

What's the air temp? What's the floor surface temp?

Each house is different.

Different rooms in the same house are different.

Single pane windows?
Metal, wood, composite windows?
Good insulation in the walls?

Experiment. Turn it up to 11 and see what happens.
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neilpilot
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Re: Temperature setting for radiant floor heat

Post by neilpilot »

My radiant heat system was installed between subfloor and ceramic tile, only provides supplemental heat to the room, so I can't provide useful information to answer your question. However, I would be concerned that, if you live with even moderate summer humidity levels, the wood floor will enter the summer with unusually low moisture content and be subject to swelling and deformation.
Valuethinker
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Re: Temperature setting for radiant floor heat

Post by Valuethinker »

dodgy55 wrote: Sun Nov 19, 2017 8:20 am My kitchen only had a toe-kick element under the sink cabinet as the source of heat. I found this very inadequate and after some research I opted to install radiant floor heat in my kitchen. My kitchen floor is the old fashion 3/4" oak flooring. It was a semi-DIY project. I purchased all the components online. I installed the pex tubing under the kitchen floor and had a professional plumber tie the tubing and circulating pumps into my existing natural gas boiler. I find that my floor is toasty warm but the ambient air temperature is still on the cool side. The thermostat is now set at 95 degrees. Temperature is controlled by a floor probe in the under-floor sheathing. Not sure if I need to raise thermostat setting. I am curious as to the experiences of other BHs with wooden floors heated via radiant heat.
Heated bathroom tile floor (electrically heated). Bathroom has modern insulation standards (rest of the house does not though, so it's likely there are cold bridgings and there certainly is to a loft space which is typically c. 20-30 degrees F cooler, door hatch in wall of bathroom). Half window across the back wall and a (triple glazed) skylight-- so those would be real heat holes.

We were told a towel rail (hot water heat) would be enough but it is not. Had to replace with a rad ("emitter" in the jargon).

Does not really heat the room though even at 37 degrees C (98.6F). You may find for safety reasons the setting does not go higher than that?
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onthecusp
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Re: Temperature setting for radiant floor heat

Post by onthecusp »

We installed a very similar system in an older house that we previously lived in. Loved it.
Before we had a single old fashioned radiator in the kitchen and essentially un-insulated breakfast nook. It was a large kitchen and with the floor heat it was very comfortable. The nook had the floor heat too but was a bit away from the radiator and stayed just a bit cooler with all the (older) windows.

1. Think about simple insulation fixes.
2. Consider a radiator, it heats the air directly and could be piped into your hot water system. Your thermostat is probably measuring water temp and the actual floor is a pretty good insulator so the surface is probably only about 85 which won't heat the air fast enough unless your insulation is ideal.

In edit: Our old fashioned cast iron radiator was hot to the touch but not dangerously so, surface temp was probably about 110F or so.
Uniballer
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Re: Temperature setting for radiant floor heat

Post by Uniballer »

So you're pumping a lot of heat into the tubing under your kitchen floor, but it isn't making your kitchen very warm. What is under the kitchen floor (e.g. basement or crawlspace)? Did you install insulation below the tubing to make sure the heat goes up into the kitchen?
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PaddyMac
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Re: Temperature setting for radiant floor heat

Post by PaddyMac »

Our experience with radiant heat is different; it runs under mostly tile, and some carpet (in bedrooms). We leave it around 70 in the winter, and the house is very comfortable. A few nights a year we might kick on the gas fireplace, but only when the sun doesn't shine (it shines most days in New Mexico, even in the winter). Temps are getting down to close to freezing at night. We love radiant heat - especially having warm tiles in the bathroom!
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CaliJim
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Re: Temperature setting for radiant floor heat

Post by CaliJim »

Uniballer wrote: Mon Nov 20, 2017 10:07 am So you're pumping a lot of heat into the tubing under your kitchen floor, but it isn't making your kitchen very warm. What is under the kitchen floor (e.g. basement or crawlspace)? Did you install insulation below the tubing to make sure the heat goes up into the kitchen?
yes... good question... and not just insulation under ... but reflective insulation and/or reflective heat transfer plates under the tubes to drive the radiating heat UP.

Image

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but he did say the floor was warm... but the air not so warm.... so I suspect cold outside walls and leaky windows.
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IMO
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Re: Temperature setting for radiant floor heat

Post by IMO »

Uniballer wrote: Mon Nov 20, 2017 10:07 am So you're pumping a lot of heat into the tubing under your kitchen floor, but it isn't making your kitchen very warm. What is under the kitchen floor (e.g. basement or crawlspace)? Did you install insulation below the tubing to make sure the heat goes up into the kitchen?
So even if the floor is warm, it could be attempting to heat both inside your house and the space under your house.

Having a history of radiant floor heating in a concrete slab, with areas of carpet padding/carpet above the padding, once the concrete slab gets up to thermal temperature, the temperature would be set/kept around 72 degrees for a comfortable level of heat in a relatively well insulated home with modern windows.

I do believe wood is a poor insulator (your oak floors), and not would not hold thermal heat like a concrete slab. Thus, it does seem odd that you are having to put the temp setting so high because in theory the heat would be making it into the interior living space of your home.

I would recommend going to somewhere like Harbor Freight and spending $30 for a digital thermometer. Start shooting readings off the floor surface centrally and near external walls/windows, and even at ceiling. If there's a crawlspace underneath, you could shoot some temperatures from underneath and to external foundation walls. I would want try to figure out where all your heat is going and getting some various temperature locations would help problem solve for things like poor insulated areas. (Maybe the crawspace is getting heated and that heat is going out areas on the foundation walls?)

Also, there can be issues with different types of wood floors relating to use over radiant heat due to drying/splitting from the heat. Not sure where oak floors fall into that concern.
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dodgy55
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Re: Temperature setting for radiant floor heat

Post by dodgy55 »

After reading the several responses to my original post it occurred to me that my cellar is also toasty warm. This would mean a lot of heat is being distributed downward as well as upward. The pex tubing does have a thin piece of metal shield to hold the tubing in place as well as to radiate the heat upwards. Also have installed 3" kraft faced insulation in each joist bay. Should probably consider a more effective method of blocking heat from leaking into cellar. Am thinking of adding a 1" foil face rigid insulation board in each joist bay. Are there any better alternatives?
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CaliJim
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Re: Temperature setting for radiant floor heat

Post by CaliJim »

dodgy55 wrote: Tue Nov 21, 2017 8:34 am After reading the several responses to my original post it occurred to me that my cellar is also toasty warm. This would mean a lot of heat is being distributed downward as well as upward. The pex tubing does have a thin piece of metal shield to hold the tubing in place as well as to radiate the heat upwards. Also have installed 3" kraft faced insulation in each joist bay. Should probably consider a more effective method of blocking heat from leaking into cellar. Am thinking of adding a 1" foil face rigid insulation board in each joist bay. Are there any better alternatives?
Move kitchen to basement?

I think adding foil faced rigid insulation, foil facing up, 1" or less below the pex, air gap, no contact for conduction, would be worth trying. The add back the fiberglass batt back, below the rigid insulation, if there is room.
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Liberty1100
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Re: Temperature setting for radiant floor heat

Post by Liberty1100 »

dodgy55 wrote: Tue Nov 21, 2017 8:34 am Also have installed 3" kraft faced insulation in each joist bay. Should probably consider a more effective method of blocking heat from leaking into cellar. Am thinking of adding a 1" foil face rigid insulation board in each joist bay. Are there any better alternatives?
Adding insulation would help. Focus on the R-rating of the insulation (like R-19 or R-13). You want a higher R number, but only if it makes economic sense (diminishing returns).
Mountain Fiddle
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Re: Temperature setting for radiant floor heat

Post by Mountain Fiddle »

In hindsight, a good heat load calculation, taking insulation, windows, air infiltration, floor thickness, etc. into account, can tell you how much floor area of radiant you need at a given supply temperature to heat the room. I've found that in colder climates, rooms with a lot of glass and exposures can be difficult to heat with staple-up radiant (as opposed to gypcrete or similar). This is especially true in kitchens where you have a big volume, but not as much floor space due to cabinets.

If the ratio of your floor area to heat load is too small, you have three choices:

1. Decrease the total heat loss via better insulation, air sealing, etc. (preferred)
2. Add a bit of additional supplemental heat, such as the old toekick heater or a small radiator.
3. Improve the heat output of the staple-up. Since we can't go much higher with our supply water temperature without causing floor damage or uncomfortable temperatures, the only choice here is to add conductive plates and/or insulation under the floor.

Avoiding nighttime setbacks and using space temperature instead of floor temperature for control could also help, although you still need to limit your water temperature somehow.
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