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Community and Q&A

Bathroom Heating Options Working with Heatpumps

Matt_newyork | Posted in Energy Efficiency and Durability on

What is the most efficient way to heat my bathrooms?

I’m currently renovating a 5100 sqft house from 1960 in Narrowsburg, New York. Currently, there are hydronic baseboard radiators fueled by oil. I’m planning to install mini-split heat pumps as a primary heat source. I’ll keep the oil heat as a backup. I’m also planning to upgrade the insulation with pour-in-place foam.
I’m told the bathrooms are too small for mini-splits. I’m considering installing FAR infrared film by Warm Wave under the new tile floor rather than baseboard or wall heater.  Do you think this is a efficient and effective idea? I’m having trouble finding reliable information that isn’t only provided by a reseller or manufacturer about this technology.

Than you,


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  1. mr_reference_Hugh | | #1

    Do you think this is a efficient and effective idea?

    Normally electric heating solutions are 100% efficient. Electrical wiring can be brought directly to the bathroom and the equipment can be sized perfectly for the heating requirement. This zoned type of heating solution is efficient for another reason, it can be controlled independently.

    You could always look at standard electric wire heated floor. Or you could look at infrared heat panels that can be placed on the ceiling (out of the way) to radiate heat downward.

  2. Expert Member
    Dana Dorsett | | #2

    >"...planning to upgrade the insulation with pour-in-place foam..."

    Proceed with caution! Pour-in foam has lots of associated risks, and some are VERY environmentally unfriendly. Once the foam has set it can be nearly impossible to remove or correct any errors.

    What sort of construction are you working with (wood-framed studwall? Concrete block cavity wall? Something else?)

    >"I’m considering installing FAR infrared film by Warm Wave under the new tile floor rather than baseboard or wall heater. Do you think this is a efficient and effective idea?"

    The heat loads of bathrooms are usually quite load, and even though radiant electric floors aren't very efficient (about 3x the amount of power use compared to better-grade heat pumps) comfort levels are good and the heat loads are usually WAY too low for a dedicated mini-split head to operate efficiently.

    In a well-insulated home with only modest amount of window, a bathroom in any location other than an exterior corner may have a low enough heat load to not really need any dedicated heat at all, but a radiant floor properly sized for the actual design heat load for that room can be a nice comfort touch.

    Bottom line: Like any other heating system, you need to run the room-by-room load numbers to get it right. Oversizing "just in case" leads to lower comfort, lower efficiency. Since you are planning to heat with heat pumps, use the BetterBuiltNW load tool, which is pretty good for right-sizing mini-splits correctly, way better than most online freebie tools (or even pro-tools in the hands of the average HVAC designer):

    In parts of northern Europe infra-red panels (which don't work with floors, but ceiling & wall mount models do) are becoming a popular in-between option. In practice when right-sized they use about half the annual electricity as electric panel-rads or baseboard, but are nowhere near as efficient as a heat pump. They're more expensive than electric panel radiators or electric baseboard, but the comfort comes on fast- faster than waiting for air convection to heat up the room.

    Right-sized (for the design load) panel radiators are cheap, and while not quite infra-red class, are way more comfortable than electric baseboards. One of the easier to find vendors of pretty good inexpensive electric panel rads in the US is Amaze (, which come as small as 250Watts ) ~850BTU/hr, which is about right for a bathroom. Most inexpensive line voltage thermostats can work with this type of product. (Earlier this year I specified a 600W version from that vendor to heat the master bedroom + bath part of a double-wide mobile home heated primarily with a mini-split on the other end of the house. It seems to be working out just fine for them. There was an initial odor/outgassing issue when operating, but that has disappeared with use.) Most electric panel rads are paintable, infra-red panels not so much.

    1. mr_reference_Hugh | | #3

      I would just second what Dana is saying about infrared panels on the (on the ceiling). "They're more expensive than electric panel radiators or electric baseboard, but the comfort comes on fast- faster than waiting for air convection to heat up the room."

      We were originally considering a single heat-pump head in a central location with infra-red panel heaters as a backup in bedrooms and bathrooms. Since ours was a new build, we ended up going with a ducted heat pump system, with a supply boot in the bathroom. Part of our constraints were that our provincial code (enforced by city inspectors) require a source of heat in every single room.

    2. charlie_sullivan | | #4

      Any heated panel is going to transfer heat via IR radiation and convection. So how do the ones in Europe allow lower energy consumption than the ones available in the US? I don't know, but here's one possibility: they are higher power than what you would want to match the load of perhaps 860 BTU/h. That allows you to turn it on when you enter the room, have immediate comfort, and turn it off when you leave, or turn it down if you are there for a while, using less energy than if you'd turned on a lower power heater an hour ahead of time to ensure comfort when you walk in.

      If that's the case, what's special about them isn't the technology, but rather the sizing choice, a choice that could be made with any panel heaters, as long as they don't take up too much space to achieve the needed power level, and assuming they have sufficiently low thermal mass to heat up quickly.

      1. Expert Member
        DCcontrarian | | #5

        Yeah, I'm dubious of any technology that claims to produce "better quality" heat that provides more warming per unit of heat. Maybe this time is different, but those claims come and go and they never seem to stick around.

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