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Recommendations for Supplemental Heat in Bathroom

joenorm | Posted in General Questions on

Hi All,

I am finishing up a new build, 1450 Square feet, zone 4C.

The house is laid out so that a single head mini split can heat the entire home, so far it is working great. I also plan to install a wood stove soon as wood is abundant.

The one spot that might like to be a little warmer on occasion is the upstairs bathroom. It is the furthest from the MiniSplit blower and will be cool(maybe even cold to some) on very cold days.

Wondering what the best option for a little occasional heat here? Floor matt is out of the question. I am thinking maybe a little wall mounted heater of some kind? Maybe a heated towel device that serves as a heater that can be manually controlled?

Another idea would be a little transfer fan, as the lower wall of the bathroom is actually part of the upper downstairs wall(vaulted situation). The air would be warm up here being a high spot. One concern with the fan idea is not transferring sound between the two areas of the home.


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  1. 1869farmhouse | | #1

    I’ve installed a little Cadet, in-wall mounted heater in every home I’ve ever lived in. They make a 1000 watt and I believe a 1500 watt that only require 120 volts. Very simple and effective for occasional spot heating.

    Transfer fans seem to only work in theory. Something about the delta (difference in temperature?). Basically it takes a ton of 72 degree air to warm 65 degree air.

  2. onslow | | #2


    Wall heaters in bathrooms have one critical requirement, no possibility of towels or robes being hung in front of them. I know of two instances of new robe hooks being placed above heaters without thinking. The robes fortunately smelled badly as they melted/toasted while the people were present. A towel bar above a heater would present the same risk. It would be easy to set the heater going and leave while the bathroom warms up only to have a real fire by one's return.

    The RBF Cadet model appears to be an improvement over the wall heaters I have extracted during remodels. Many of the old ones had heater wire quite close to the grille face like a toaster. The RBF parts diagram suggests air is drawn inward by a small squirrel type fan, which forces the air across a small heater coil. I still would not want to risk having a towel or robe dangle in front of the unit though.

    Another thing to consider is the level of fluff and hair present in a bath (or most rooms at our home). Fan flow will make sure fluff is dutifully inhaled. At minimum the airflow can fall dramatically over time. Just plan on regular cleaning and inspection of any grilles or filtering grids.

    Non-fan based heaters will likely prove disappointing at providing heat quickly. They can act as a stabilizing booster for the general heat supplied by the mini split, but producing the quick cozy feel of warmer air at bath time pretty much a fan heater's forte.

    Towel heaters can be had as electrically heated glass panels or oil filled tubing arrangements. Either will warm a towel nicely for a luxury bath experience. The glass ones are pretty pricey if I recall correctly. They would not be good general heat boosters as towels presumably stay on them.

    Last note, as the air in the bathroom fills with warm humid air from shower or bath the perceived warmth of the room goes up. It is a matter of personal comfort and perception as to what constitutes a warm bathroom. Size accordingly.

    1. 1869farmhouse | | #3

      The Cadet heaters all come with a thermostat. I always just crack mine into the on position. Even I did forget to turn it off, it would shut off on its own around 74.

      There are a lot of things in a home that have a million variables to stress over - in my opinion, a spot heater is not one of them. Simple solutions are often the best solutions.

  3. Expert Member


    You can wall mount this and take it down for nine months of the year.

  4. Expert Member
    BILL WICHERS | | #5

    There are bathroom exhaust fans that also have a heating function. I have one in my master bath and it’s nice when taking a shower during an off time of day when the rest of the house is kept at a lower temperature (we use various setbacks so that we minimize our heating use while we’re at work or otherwise away from home).


  5. Expert Member
    Akos | | #6

    Can't go wrong with floor heat. I love getting up in the morning and walking onto 26C (79F) tile. Go with one of the better floor mats (ie ditra heat) and you won't regret it.

    1. Expert Member
      BILL WICHERS | | #7

      Akos, since it sounds like you have the Ditra system, did you do the install with the heating wire that snakes around the "squares" of the Ditra membrane? I've been thinking of this system myself for an upcoming bathroom renovation and I'm curious what your opinion is of the entire system.


      1. Expert Member
        Akos | | #8

        Mine is hydronic at home. If you are running hot water recirc and the ceiling bellow is open, you can do a pretty simple floor heat by serpentineing the recirc return pipe bellow with a couple of heat plates.

        My neighbor did an install with the ditra system (squares + serpentine wire) and it seemed much sturdier than the typical floor heat mats. For something that is hard to service, it is worth to spend a bit of extra money.

        Make sure you read the fine print for the warranty, you need to use their thinset and I think it needs a hipot test as well.

      2. STEPHEN SHEEHY | | #9

        Bill. We have Ditra heat and it works well, for the one of us who likes toasty feet in the shower. It takes about 20-30 minutes to warm from 67 to around 74°. Floor is insulated under the tile.

  6. Expert Member
    BILL WICHERS | | #10

    Akos and Stephen: thanks for your replies. Sounds like the Ditra heat system is a good option. I’m aware of the tests they require for the warranty since I was looking into their requirements. Hipot is easy for me since I have that equipment available to me from work.

    I like the radiant heat idea with a hot water recirc loop. I have a shower on an exterior wall (pipes are in the inside wall, but the shower tile gets cold) that we want to heat. I might try extending my hot water recirc loop for a temporary setup until we renovate that bathroom. I can use a solenoid valve to bypass it when we don’t want it running.


    1. Expert Member
      Akos | | #11

      For the recirc based heat, you don't want a bypass valve. Since it is potable water, you need to circulate water through it to keep it from stagnating. The simples is to use something like th115-af-120s to run your recirc pump with the floor heat sensor on the pipe after it exits your heated area.

      In the winter, set the floor heat setpoint to whatever temperature you prefer, in the summer time set it a couple of degrees above ambient.

      This way it will still occasionally pulse the pump to flush out cold water but won't run enough to deliver any meaningful heat.

      If you program in a schedule, it can also be set to run only when you are at home.

      1. Expert Member
        BILL WICHERS | | #12

        Good point about stagnant water. We’re on a well here too, so doubly concerning with no chlorination.

        I use a thermosyphon system on my recirc loop, so no pump. I could put a solenoid valve on the system to stop it, but then I lose the quick hot water function (which we really need). Our hot water heater is on the opposite side of the house from the master bath, and is a run of 1” copper pipe. This means LONG wait times for hot water without the recirc loop running. I added the thermosyphon recirc loop shortly after we moved in here to address that issue.

        There is always something to make things hard ;-) I might try a small electric system instead of the water loop.


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