Underfloor Heating (Wet and Electric)

[decker99]

I am in the process of having an extension built at the rear of my property. We have knocked the outside wall down so we have a large L shaped room consisteing of the existing kitchen (original house) plus the new extension.

The proposal put forward for the UFCH was for a wet system (Polypipe) for both parts of the building (new and existing). Both rooms would have had separate controllers so they would be independant. However we now have an issue because the screed that has been taken up in the existing part of the property is not deep enough for the wet system (can only get 20 -30 mm of screed) and no insulation.
The only way to get the correct depth would be to break up the concrete slab and lay a new properly insulated slab to the correct depth which I suspect will be fairly costly.

I am wandering if there are any issues if we install wet UFCH in the new build part and electric UFH in the existing part of the room.
Obviously the two systems won't come into contact with each other so I suspect its is OK but would like proffesional advice.


Regards

 

[stem]

I'm not an underfloor heating professional, but having gone through the same scenario as you three years ago, and conducted quite a bit of research, the following may help you.

The electric heating you choose needs to be powerful enough for the job. Be careful, the low wattage mat type versions are just designed to warm a tiled floor so that it's not cold to walk on, and require additional space heating to achieve a decent room temperature within a reasonable time.

Also, with a kitchen, much of the floor space is covered with cupboards, fitted appliances and maybe a island etc., that prevents much of the heat from the floor underneath them escaping into the room. For me, even the largest wattage heating mat I could find at the time, wouldn't have given enough heat for the whole room from the relatively small remaining exposed floor space.

So I tried a full underfloor electric heating system, the type with buried elements. That was available with a high enough output, however, like the wet system it needed to be installed deeper than the space I had available. Finally I worked out the expected running cost and installed radiators.

The manufacturers would be in the best position to advise the suitability of their product for use in conjunction with other types of heating. I imagine that as most types of electric underfloor heating can be installed in kitchens and bathrooms where there is a possibility of leaks and spills from other pipework so I think they should be safe in such an environment.

 

[mointainwalker]

If you go ahead with either water or electric UFH without insulation , you will be wasting a very significant amount of your energy bill.

The above poster talks about heat beneath cupboards etc being lost : it is generally accepted that that do not heat beneath cupboards.

Sorry, I know little about electric UFH so cannot help further.

 

[nad000]

i wouldnt waste your time on underfloor heating, it is worthwile having a wet system but its effective if its in the whole ground floor of the house seperated into different zones, it takes longer to heat up but you get a nice constatnt temperature in the whole area of the house. splitting the area and mixing it with electric wont be a worthwile move, you will have different outputs, in my opinion its too much effort for little return, I have installed a wet polypipe system in my house and was faced with the same problem, Kitchen and rear extension was new slab and remainder was old, so what i done was dug the whole ground floor, insulated it 150mm, layed the first concrete slab, followed by 35mm kingspan foil boards, damp proof sheet, heating pipes, i had to use special screed called Flowing screed 65-70mm.
Then to top it all i had to use special adhesive for the floor tiles, costing £30 a bag. The finished product is good but was it really worth the headache and money, should have just installed some good quality designer radiators.
so in my opinion dont do it, just get a couple of good quality high output designer rads

 

[dextrous]

Why not install a hybrid system - UFH in the new floor and a rad (or even kickspace heaters if it's to have kitchen units) in the existing bit?

 

[mointainwalker]

@nad000

"...and then to top it all, I had to use a special adhesive ...."

You make it sound as if that was a surprise - you must have known that early on - standard procedure.

 

[stem]

The above poster talks about heat beneath cupboards etc being lost : it is generally accepted that that do not heat beneath cupboards. Sorry, I know little about electric UFH so cannot help further.

Actually that was my point. You don't install heating under cupboards because the heat would be lost. Therefore all you have to play with is:

The relatively small remaining exposed floor space.

 

[huw169]

I also looked at electric UFH for my full refurb and decided that it was not worth the money. Contacted a sparky mate i know for advice and fitting and even he told me not to bother.
Then talked to a plumber mate about wet system, and he told me the same. Was happy to do it for me, but would recommend it.
Got a couple of designer rads in the end for the ones that are seen and standard screwfix for the rest.
Very effective.

It does depend on your personal situation though. I had suitable wall space for rads.
Let us know what you decide and what you think of the system once installed - if you go for it.