Underfloor heating on new and existing space

antonia_n · 1 Jul 2023

My partner and I just started building a 4mx7m rear extension. We plan to knock two walls down so the extension is part of a large open plan space along with the current kitchen/dining room (also 4mx7m). We've already decided to install wet UFH on the new part, but we are struggling to decide what to do on the existing half. The options we are considering are:

- UFH on the extension and radiators on the existing part.
-Dig out the floor in the existing part and have UFH everywhere. We are concerned about the mess and cost for this option.
-Normal UFH on the new part and an overlay system on the existing. This seems like a good option potentially but not sure if the two systems would work together well and what is the cost of running the overlay system.

Any advice?

The house was built in the 80s and it's in the south UK. Thanks!

SpecialK · 1 Jul 2023

Dig out the floor and have UFH everywhere.

antonia_n · 1 Jul 2023

SpecialK said:
Dig out the floor and have UFH everywhere.

Have you done this? Do you have any idea of the cost/time required for it per square meter?

Mr Chibs · 1 Jul 2023

I'm with Special K, after having it in my kitchen, I'd never go back to radiators.

That said, it may depend on your floor covering, I have stone floor in kitchen UFH is well suited to this... not so on carpet.

antonia_n · 1 Jul 2023

Mr Chibs said:
I'm with Special K, after having it in my kitchen, I'd never go back to radiators.

That said, it may depend on your floor covering, I have stone floor in kitchen UFH is well suited to this... not so on carpet.

We have laminate everywhere, no carpets. Did you retrofit the UFH?

Mr Chibs · 2 Jul 2023

No installed from new in screed, but you can use spreader plates for other areas.

I have found running costs to be as cheap as it can be.
Only thing is you have treat it differently, i.e. if it's chilly in the morning as you had it set too low, it can take an hour to get warmer.
It just a case of getting used to it, and setting things to come on earlier.

I now have mine set to 18ºc and just let it come on and off at will. (other than summer, when it's off).

Check your laminate is compatible with it before purchase, there is a large free pdf from polypipe all about UFH, screed, spreaders etc.
Mine is polypipe system with red trays, so far it's been excellent.

antonia_n said:
We have laminate everywhere, no carpets. Did you retrofit the UFH?

Exedon · 2 Jul 2023

We are polypipe registered underfloor installer's, I would grit teeth and take up existing.
Get benefits of a fully insulated floor.
If your installer contacts polypipe then emails them a floor plan you will get a full specification and pipework layout back normaly same day. All at no cost then you get back up of a manufacturers warranty.
You run underfloor with a maximum backset of 4C below desired room temperature.

SpecialK · 2 Jul 2023

antonia_n said:
Have you done this? Do you have any idea of the cost/time required for it per square meter?

No I only have UFH in the extension. With UFH ideally you need to run it differently to rads. During the winter I start mine 4 hours before the radiator heating comes on which leads to the extension being warm and trying to heat the rest of the house as its semi open plan.