what wattage for a small bathroom?

[xelaris]

The bathroom area is about 2.5 sqm but the available area for laying an electric mat is only 1.3 sqm....apparently the best option is to have about 150w per sqm - so in my case I should look for 375w - should I go for the more powerful mats/cables? - I've seen some cables are rated 10w per linear meter and others 15w....ditto for some mats: some are rated 150w sqm and others 200w sqm (which apparently is only a question of having the same cables spaced a bit closely). If so, wouldn't be better to opt for cables and choosing the closest (more concentrated) pattern?

It is possible to increase the heating area by removing some tiles (some hard work needed) - this area is going to be covered by a shower cubicle...this might be relevant as the cubicle takes probably a quarter of the bathroom (less area/volume to be heated? If so, less wattage needed?)

 

[xelaris]

btw: the bathroom is facing South/East and has 3 external walls (West, East and South) and a double glazing window.

Thanks in advance for any advice.

 

[Ajax123]

Sounds to me like UFH is a waste of time here. The heat output from the limited floor area is likely to be less than the heat loss from the room itself making the UFH overworked and inefficient. Have you done any heat loss calcs to see if it is worth it?

 

[xelaris]

Sounds to me like UFH is a waste of time here. The heat output from the limited floor area is likely to be less than the heat loss from the room itself making the UFH overworked and inefficient. Have you done any heat loss calcs to see if it is worth it?

No proper calculations done...I've just checked some posts of similar bathrooms (the actual sizes are 1.75 x 1.45 x 2.2) - but it looks like the available area is just too small (about 50% of the whole). As I've mentioned it is possible to increase the available area to up to about 2 sqm.....that way it is possible to install a 400w mat.
Another option would be to install an electric towel radiator for winter - if I get 250w from the UFH cable/mat and 150w from a radiator?

 

[Ajax123]

You would be wise in my opinion to sort some proper heat loss calcs to make sure it won't still be cold. Perhaps the UFH for background heat and a rad as you say might be the answer but if you pump 400w/h into the room but the room loses 500w/h it will never get warm.

 

[DHTiling]

If the substrate is timber , then 100w per mtr is max , if insulated then 150w.

 

[xelaris]

You would be wise in my opinion to sort some proper heat loss calcs to make sure it won't still be cold. Perhaps the UFH for background heat and a rad as you say might be the answer but if you pump 400w/h into the room but the room loses 500w/h it will never get warm.

originally there was a small radiator (from a gas central heating system) - the bathroom felt a bit cold during most days of winter, but there was no insulation - while now there is wall and roof insulation....suggestions for conservatories is 200w sqm - I guess this should also apply to my bathroom too which is basically an extension facing south.

 

[xelaris]

If the substrate is timber , then 100w per mtr is max , if insulated then 150w.

I'm dealing with a concrete floor....there are 200w/sqm mats too - in fact in my case I think I'd like to use an even higher wattage mat (which doesn't exist or is just unsafe/not practical?)

 

[DHTiling]

I'm dealing with a concrete floor....there are 200w/sqm mats too - in fact in my case I think I'd like to use an even higher wattage mat (which doesn't exist or is just unsafe/not practical?)

160w is what you need..

 

[Time's Ran Out]

Thermonet do a 200w mat.
Remember you have to walk on it so 25degrees is comfortable and it will radiat the heat but 1sq mt is pretty small.

 

[xelaris]

160w is what you need..

Do you mean I can use the available 1.3 sqm to heat a 2.5sqm x 2.2m volume? Do you mean the total wattage or 160w x sqm? In the latter case it would make 160w x 1.3 = about 200w (that would be great).

 

[xelaris]

I forgot about an important factor....there are Marmox boards covering the whole area - these are about 30mm thick.