Electric underfloor heating in a bathroom

[platforminc]

Hi all,

I have a bathroom which is quite small I'm size, the overall size is 2.4m x 1.7m. It will have a bath 1700mm x 600mm. It will also have a vanity set which is going to be another 300mm depth. The space in the middle will probably be 1.5m x 1.5m or 1.5 x 1.7m tops. This will all be on a suspended flooring within a timber frame construction.

I will like to have a small electric underfloor heating. I have no experience of them, I wanted to know which type/make one should be looking at and whether there are any gotchas to be wary of.

Do the electric underfloor heating mats also work with timers as I only plan for it to come on for 30 - 45 mins daily during the week.

I will also have a normal central heating radiator in the bathroom as well.

Thanks in advance .

 

[ericmark]

No point it takes 45 minutes to warm up.

 

[flameport]

Yes it can be used with a timer.

However - what do you expect / want it to do?
2m² will be totally inadequate for heating the room, so the best you can expect is for it to warm the floor slightly - and that's assuming the floor is fully insulated under the heating elements, and it's been switched on for long enough.
Electricity is also the most expensive option for heating anything.

 

[ericmark]

Fitted electric underfloor heating in mothers wet room mainly to dry floor as she was an amputee and did not want her to slip, it was really a failure, there are two types of under floor mat, the rayochem auto compensates so will not over heat, but when we fitted it, you could not get it in an earth braid which is needed in a bath room or wet room, the simple resistive is available with braid, however need a pocket with a sensor in to stop over heating, the temperature limit for the floor is 27°C and with a bath room you want the room at 22°C so only 5°C differential, you often have an extractor running when in use which is drawing in air from rest of house at likely 19°C in mother case more like 18°C as from the hall, and the under floor heating could not raise the air temperature to 22°C however long it was on even with the fan off and the floor had 9" of insulation, it needed the towel rail running to heat the room.

As to floor if you moped floor it would dry in around ½ hour, if you instead used the under floor heating dry in 1½ hours, and if you used both dry in 25 minutes, once the shower cooled the floor it took ½ hour to even work out it was switched on, an hour before you could feel any warmth, and 2 hours to reach full temperature.

An inferred heater is far more effective. Directed at floor it will heat it, and is an intent heat.

 

[Diver Fred]

I have EUF in bathroom. As others have said yes you can have a timer - in fact the controller is most likely to have one built in. I have it on for approximately 3 hours a day - 2 in morning and one in the evening. 4 SqM of 200w (PSM).

Do you expect the heater to warm the room or to take the 'chill' off? Certainly the warm floor is really good. How effective is the rooms insulation? My bathroom has 40mm of wall insulation and 100 in ceiling with a warm loft. The wife does say she'd like a second form of heating in the bathroom on the coldest days.

You can buy mat or cords & layout mat. Plan out the bathroom layout with accurate measurements on paper. Then reduce that floor plan by drawing another line 100mm inside the wall lines and that area inside those lines will give you the area you can heat - the elements need to be 85mm from all walls and any fixed object including toilet and sink pedestal. I'd say layout mat and heating cord would be the better way for you to go.

With your small area you should aim to get the highest mat power you can (200 or 250 watt PSM).

I'd say you will need 18mm Marine ply on the wooden floor. Then 10 or better still 16mm floor insulation before the the floor is constructed. That will raise the floor level.
You have normally fit the control unit outside the bathroom with a underfloor measuring device in the matting.

My floor takes roughly a hour and half to get up to temp (22 degrees) in the mornings. I say it uses 2 units per day for the time I have on. Haven't noticed a big increase in bills.

 

[platforminc]

I have a very difficult decision to make.
I usually dont like using ply in bathrooms, instead I like to use 6mm or 12mm cement boards. will this work in my case ?

In terms of insulation, the bathroom wall is insulated externally, as its timber frame with 100mm celotax, the loft has 270mm insulation, and the floor we intend to have 100 mm sound insulation, and the bathroom walls to also have 100mm sound insulation.

I will have a secondary heating (normal towel radiator), the purpose of the underfloor heating it to take the chill off the tiles especially in the morning, hence why it will only come on in the morning.

Thanks in advance.

 

[winston1]

the purpose of the underfloor heating it to take the chill off the tiles especially in the morning, hence why it will only come on in the morning.

Have you thought of comfy slippers? Much cheaper and very effective.

 

[Taylortwocities]

Put an electric fan heater (bathroom type) on the wall.
Easier
Cheaper
Effective

 

[platforminc]

Is this to keep the bathroom warm or warm up the tiles ?

I ask this because I intend to have a normal central heating bathroom radiator.

Put an electric fan heater (bathroom type) on the wall.
Easier
Cheaper
Effective

 

[Taylortwocities]

I ask this because I intend to have a normal central heating bathroom radiator.

You might have mentioned that in the first place!
Most of us thought you wanted the UFH as the sole heat for the room.

They are ok if you just want warm tootsies. I prefer Warmup. You need to prepare the subfloor. What is that made of? You need to prevent most of the heat disappearing into the under floor instead of heating the tiles.
Supply circuit MUST be RCD protected. I would advise you use a registered electrician to carry out the electrical work.

 

[platforminc]

Apologies for the confusion.
The subfloor is a suspended floor which at the moment is just a 7" floor joist and 6 inch wide floorboards, its a new build so I have the opportunity to design the construction. Normally without electric UFH, I would level the floor, then install 6mm cement boards on the floorboard, then tile ontop of that.

What I would like to find out from the lovely people on this forum is, will the procedure be different for UFH ?

Thanks in advance.

You might have mentioned that in the first place!
Most of us thought you wanted the UFH as the sole heat for the room.

They are ok if you just want warm tootsies. I prefer Warmup. You need to prepare the subfloor. What is that made of? You need to prevent most of the heat disappearing into the under floor instead of heating the tiles.
Supply circuit MUST be RCD protected. I would advise you use a registered electrician to carry out the electrical work.

 

[Taylortwocities]

Choose your flooring manufacturer and follow their instructions. They will require a layer of thermal materials under the UFH to reduce heat loss into the subfloor area.
If you plan it properly you can make the UFH + tile level to gd the same as the adjoining floor. You don’t really want a step up!

plan your electrics carefully. Decide on cable routing including the floor heat probe. Install it in a suitable duct (usually provided with the floor kit. Even better, install two probes so that you have a spare if and when the first probe fails.