Radiant floor / ditra heat options $$ [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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01-01-2017, 10:42 AM
Hey all,

I'm remodeling a house with two small bath rooms. One is 26 sq ft and the other is 40. The smaller being a half bath and larger being a fiull bath with shower.

It leaves about 16 sq ft/ 24 sq ft of heatsble area in the baths respectively.

I want to put in radiant floor mats or wire setup to warm the floors as they sit on a concrete slab.

I see that ditra has a system incorporating the heat wire into the membrane and has a thermal break . I've also looked at sun touch, thermosoft, etc products.

I love schluter products and use kerdi/ ditra on all my tile work but the ditra heat system seems extra pricey? Any opinions out there on whether it's really worth it as opposed to just installing ditra and a floor heat system?

I feel like it will close to double cost of the system to go with ditra heat tb. Raising the floor height isn't a huge deal so that's not a big concern to me.

Just looking for opinions on the best setup without spending tons of$$ if not necessary.


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Tiger Mountain Tile Inc
01-01-2017, 01:09 PM
I use Watts Radiant (Suntouch) wires in all my heated floors. I did one over concrete recently used the Ditra TB heat mat and ran the suntouch wire in it. I don't think Schluter likes that but Suntouch is ok with it. Also I don't like Schluter's thermostats and would prefer to buy other makes.

When you say it would double the cost what are you comparing this to? You probably would still want some sort of insulation between the slab and any kind of heat I would think?

01-01-2017, 07:09 PM
I could find a 20 sqft heat kit for about half whet the ditra heat tb costs but that was before adding an underlsyment/ thermal break.

I was considering using the sun touch warm wire with ditra heat membrane and the sun touch rep recommended it to me.

So I suppose the cost is not a huge issue. I've never done floor heat before so I suppose I'm trying to be sure I do it right without overspending $$ on a small bath in a modest house.


01-01-2017, 07:14 PM
One thing you get with Schluter is a product from a very conservative company. You'll have a redundant, spare floor heat sensor. All companies suggest you check the cables with a megometer, but Schluter requires it if you want their warranty. A simple ohmmeter can only check for continuity, but a megometer also verifies you have not damaged the insulation...something that will help ensure long-term reliability.

01-01-2017, 10:42 PM
Actually Jim, Schluter has backed away from that requirement. Now they give you a longer warranty if you check with the megger, but it's not required.

When you take into account that with the Schluter system you get a Thermal break, as well as and antifracture membrane built into your floor, the price difference is not that great.

My personal feeling on this: a modest house does not need infloor heat. That's a luxury that belongs in executive pads and up. It's expensive to install and operate. But hey, whatever it takes to make the missus happy.

01-02-2017, 10:22 AM
Thanks Pete,

To be honest I don'think it needs the floor heat either but that's is what's wanted. Can you elaborate on the expensive to run part? I thought they were fairly efficient? Especially in comparison to the electric baseboard in there now.

01-02-2017, 11:00 AM
My personal feeling on this: a modest house does not need infloor heat. That's a luxury that belongs in executive pads and up. It's expensive to install and operate. But hey, whatever it takes to make the missus happy.

I think there are certain applications when radiant floor heat makes a lot of sense. I will be installing it in a small bathroom with three exterior walls and a crawl space below. It is also the farthest room from the furnace. This room is cold! In the winter the door must be kept open at all times. I will of course be insulating it as much as possible but the radiant heat is necessary to supplement the forced air that isn't quite up to the job and cannot be improved. Just to be clear though, the floor heat will only be on when someone is using the bathroom.

01-02-2017, 01:52 PM
The calculation for how expensive the system is is fairly straight forward. You need the watts that the cable draws, multiply by the hours/day and multiply by your electrical rate.

example 500 watts x 12 hrs/day divide by 1000 to get kw. x $.15/KWH makes 72 cents per day. Most cables on concrete cost approximately $1/day. Now make that 2 rooms and you have an extra $60 per month on your power bill. That's peanuts for some folks, but would almost double my bill.

01-02-2017, 05:41 PM
An advantage of Schluter's system is that there is less mass because of the air spaces (verses say embedding the thing in SLC) so that the response time is less. It still can take awhile, though. While they generally call these systems floor warming, it might be enough for room heating depending on your room and insulation, but if that's the goal, you may be disappointed! Plus, while it shouldn't 'hurt' the system to run constantly, it does cost more than running it on either a timer, or on demand. Just don't expect it to get hot like say an electric space heater which can be hot in minutes. It won't happen.

Personally, in the summer, I sort of like the cool tiled floor. Instead of electric floor warming, I installed radiant heating in that room, and it essentially warms my entire (small) upstairs as I rarely close the doors (one in the hall, one to the master bedroom).

I should also point out that in at least one state (California), it's illegal to run electric floor heating systems for more than about 1/2-hour at a time. IOW, it cannot legally be used for space heating! So, to pass an inspection, the system must have a thermostat with a timer installed. Not to say what may happen after the inspection, though!

Tiger Mountain Tile Inc
01-02-2017, 06:50 PM
with the Schluter system you get a Thermal break, as well as and antifracture membrane

This was mentioned earlier in the thread. I just want to make sure that it's clarified that Ditra Heat is not an A118.12 Crack Isolation membrane. :)

01-04-2017, 12:21 PM
Ok so it seems like there is a mix of opinion on best options. Seems like doing a mat under regular ditra is more time consuming but maybe slightly less $$ in product. Are there any other upsides to a mat under ditra vs using ditra heat with wire?

I'm open to any other suggestions as well.

Thanks for the help

01-04-2017, 12:26 PM
Running the wire through the Ditra-Heat 'studs' (Schluter's name for the little knobs built into the Ditra-Heat mats) is a piece of cake and if you need to redo it 3 times (and you will!! LOL!), it is further a piece of cake to remove and reinstall until you get it right since you can't cut the heat cable and must use all of it.

I must agree that the Schluter thermostat leaves much to be desired but it is okay.

That is a new one on me regarding the requirement for California to have a timer for floor warming systems. Crazy but I'm sure there was one isolated incident somewhere that happened to someone important person and voila, a new (silly) rule. I think I'll be skirting it for my next Ditra-Heat install...don't tell no one....

01-04-2017, 02:08 PM
That CA rule on floor warming is part of their energy conservation legislation. I dug the wording up awhile ago when it came up and posted it...don't remember where though! As I interpret it, it is because most space heating is more efficient, and they consider floor warming a luxury, thus, the requirement to limit its use. I don't make the rules...don't shoot the messenger!

01-04-2017, 02:54 PM
Here's a thread that discusses the California rule regarding floor warming:


02-01-2017, 10:09 AM
I have a question about our radiant floor system that was installed in our master bathroom 4 years ago.
Could it be the cause of staining on the ceiling in the living room below the bathroom? My husband turned the system on continuously about a month ago. Could that cause enough condensation to the cold water pipes to cause major staining along all the seams of the wallboard in the living room below the bathroom? The plumber came out today and cut a hole in the ceiling but was unable to find a leak in any pipes so far. He checked the seal in the toilet also but the seal was good.
Has anyone had this issue?

02-06-2017, 06:02 PM
Where you at, Pam? Are you in a high humidity part of the country?

Offhand, I wouldn't think the floor warming would cause the issue you are facing as it is relatively isolated from the joist bay space between the floors via the plywood but I'm just guessing. Chasing water leaks is always tricky as the water damage could be several feet from the leaking source.