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Under tile electrical heating – Schluter Ditra Heat system 2017

reedie2000 | Posted in Green Products and Materials on

Clients have asked me to install under tile electric heating. I’ve hear good things about the Schluter Ditra Heat system, however I’ve also read two things that worried me when this system was new to the US.

1. The thermostat only allows the heat to warm up to 84 degrees. You might feel this on your feet but it seems unlike to warm or dry the air above, even as a secondary heat source. Other systems allow 104 degrees. Is this still correct?

2. The Ditra heat thermostats produce a very loud clicking sound that is annoying and wake some people up.

Let me know if you’d used this system or the other systems recently and the Client satisfaction. I know that the Schulter system is the easiest to install but happy customers is also important.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    I've never installed Schluter Ditra heating mats.

    Any GBA readers have feedback?

    -- Martin Holladay

  2. STEPHEN SHEEHY | | #2

    When building our new house two years ago, we had Ditra heat installed under our bathroom tile floor. It works fine and is absolutely silent. We keep the thermostat at 74. Floor stays toasty at that setting. You can set the thermostat to warm the floor or the room or both. We just heat the floor. I can't imagine heating to 84, let alone 104.
    We're happy with the Schluter system generally.

  3. bob_swinburne | | #3

    I agree with above. I have Ditra heat in my bathroom under slate tiles. It is completely silent, works surprisingly fast and actually does a great job of heating the room which has no other source of heat. set at 68 to 74 depending on kids fiddling with the thermostat.

  4. reedie2000 | | #4

    Thanks for the feedback. I assume by 68 - 74 degrees you mean the ambient room temperature and not the floor temperature. Which of the thermostats do you own? The touch screen?

    -Thanks again for the information. I convinced my Clients to go with a couple of minisplits instead of Central Air so the under tile system would really help their concerns with the bathrooms being too cold.

  5. DanCK | | #5

    I installed approx 350sq of a similar product along with shulters ditra-mat. The mat added a little more expense to the job but it was definitely worth it in the end.
    I did speak with a Schulter rep before our install and they explained that their system is not meant for room heating but only floor warming. We installed the system in an older house so we did convince the client to install another heat source in the room. In your case, depending on your location, if the home is well insulated and sealed and your heat pump is close by, the in-floor system may be enough to help keep the room toasty.
    The product I installed was from thermawire.com . Canadian company based in St. John's NL. Excellent support. The Canadian dollar is low as well so that will certainly help you out.

  6. bob_swinburne | | #6

    The air temperature of our bathroom is usually lower than the floor temperature by 5-8 degrees. If I close the door for a while, it gets much closer. I don't have a touch screen control but it is fully programmable. I just have never bothered to. Last week the power went out overnight in our house and the bathroom air temperature plummeted to the low 50's by morning. I like the cost factor of the Ditra heat as you are buying the underlayment anyway. The additional cost is really a good bargain and my electrician likes it too. He can test it and wire it up in no time at all.

  7. STEPHEN SHEEHY | | #7

    We set the floor temp to 74. The room air temp is usually a few degrees cooler. There's no other heat in the bathroom, but the house is very tight and well insulated.

    We're in zone 6. We have a minisplit in the bedroom, above the bathroom door, but don't use it much when outside temps are 30s or above, so as far as I can tell, the floor heat keeps the bathroom air warm, since it doesn't drop below 68 even with the minisplit off. We do keep the bathroom door open when no one is using it.

  8. benasp | | #8

    Don't have Ditra heat but my house is heated exclusively with staple up radiant. And the floor tile / wood never get warmer than 86 °F, that is when it's around -13°F outside.The thermostat are set to 68°F and target is reached easily in every room.

    house has 9 ft ceiling R-24 wall R-60 ceiling and a "shameful" ACH50 of 3.3, so nothing fancy here.

    If the floor can heat up to 84°F i say this is more than enought to heat the room.

  9. Expert Member
    Dana Dorsett | | #9

    Do the math (at the very least do the dumb napkin variety).

    A warm floor will emit about 2 BTU/hour per square foot per degree-F above the average room temp.

    What is the design indoor air temperature?

    What is the heat load of the room at that indoor temperature at the 99% outside design temperature?

    Unless it has an unusually large amount of window area for a bathroom, a typical 100 square foot new-construction bathroom might have 60 square feet of free floor area, and a design heat load of less than 1000 BTU/hr @ 0F outside, and a super-warm 75F indoors. The heat rate per square foot you need out of the floor would be a ratio of 1000/60 = ~17 BTU/hr per square foot of radiant floor. That takes a floor temp about 17/2= 8.5F warmer than the average room air, or 75F + 8.5F= ~84F. It makes it.

    But run the real (aggressive assumptions) Manual-J heat load & the actual free floor area numbers to estimate the peak floor temp needed to support the load.

    Tile floor temperatures of 84F aren't particularly comfortable for bare wet feet, and above 90F it's downright uncomfortable for most people.

    Avoid radiant floor under toilets, which can overheat and melt wax seals if the peak temperature requirements are too high.

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