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Thread: Bathroom heat question

  1. #1
    DIY Member idoc4u's Avatar
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    Default Bathroom heat question

    I am finishing a 10x10 basement bathroom and have extended from the furnace trunk a 6" branch duct supplying heat to the bathroom. However, I have considered supplemental electric radiant heat in the floor or a Cadet 1000 Watt in-wall electric heater operated via a thermostat.

    My concern with the mat heat under tile is that unless you leave it on, it will take a while to heat up and if you're just using the toilet then what's the point. If you're going to shower, then it is more helpful.

    The in-wall heater sounds like a good idea, they are very aesthetically pleasing and the manufacturer claims it provides heat very quickly.

    My plan is also to lay Duraceramic tile. In my experience, this type of tile is not nearly as cold on a slab as compared to clay or ceramic tile.

    Does anyone have an opinion whether or not supplemental heat in this 100ft sq. area is likely needed?

    Thank you!

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Unless heated, the tile will always feel cold. The wall heater won't help the tile much. In-floor heating if only for comfort, not keeping the room to temp doesn't need much current. I'd check warmfloors.com for some suggestions there. You could also use a timer but that wouldn't help in the middle of the night!

    Check out www.johnbridge.com for help on tiling. They have a bunch of projects where they've done in-floor heating and you can see what others have done. In-floor radiant is a luxury - very pleasant. I'm not familiar with DUraceramic (is this a floating floor?). You may get some opinions on that at John Bridge's Tile Your World site as well. In general, durability of the 'faux' tile isn't very good and their so-called grout isn't very durable.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member Lightwave's Avatar
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    If you size the heating duct correctly you won't need any supplemental heat for the bathroom. You'll need to the math to figure out how much heat you'll need (Manual J) and how large a duct you'll need to deliver that much heat (Manual D).

    In-floor radiant heating is not recommended for slab floor applications. It'll take days--not minutes--to heat up and days to cool down.

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    Moderator & Master Plumber hj's Avatar
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    Thousands, and thousands of "slab floor buildings" have in floor radiant heat. Possibly many more than those which do not have a concrete floor. But, it is not an "instant" heat source. It is designed to warm up gradually, due to the lower temperature, and then stay at the design temperature until it is no longer needed. Because it is a fairly constant heat source, it is also a rather expensive way to heat, but the comfort is the selling point, not the cost of installation or operation.

  5. #5
    DIY Member idoc4u's Avatar
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    jadnashua, Duraceramic is a brand of composite tile that looks like, is sized like and placed like ceramic tile. The advantage, in my opinion, is that it isn't as hard and cold as ceramic tile. I tiled a kitchen on a slab and it was significantly warmer and more comfortable to walk on in contrast to ceramic tile. The grout is like a caulk-type material. You glue down the tiles (available in a variety of sizes like ceramic). The thickness is similar to ceramic. You can cut the tiles with a circular saw and I believe you can score and snap them with a utility knife, but not positive. It is priced higher than ceramic tile, but in my opinion worth it.

    I was questioning whether forced air heat via one 6" branch would be sufficient to heat a 100ft sq. bathroom, or if I should supplement like with radiant heat or an in-wall electric heater on a thermostat. I like the in-wall idea, but it may be over-kill.

    Thanks for the replies!

  6. #6
    DIY Member Lightwave's Avatar
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    Quote Originally Posted by idoc4u View Post
    I was questioning whether forced air heat via one 6" branch would be sufficient to heat a 100ft sq. bathroom,
    Probably, but the only way to be sure is to do a load calculation using Manual J.

  7. #7

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    I would take the issue past Manual J. You can have a well balanced system and still have a cold bathroom, especially if on a slab, with hot air heat, and the bathroom on an outside wall.

    Another consideration would be heat lamps in the ceiling, which give you a warm feeling immediately. You could also use a toe-kick heater, which as with the wall heater, will give you a quicker heat source. I have done bathrooms where we have installed floor, toe-kick, and heat lamps as supplemental heat sources.

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