Adding wet UFH to existing radiator-based setup controlled by Evohome HR92s

[freddyq]

Hi all, hoping I can get some help on here...

I've got an existing setup of evohome in my house with 8 radiators controlled by HR92 TRVs. I am now having some extension work done and considering having wet UFH installed in 3 new rooms created from the extension. The UFH in each of these three new rooms will need to be controlled independently. I've been reading threads on here about people who have been in a similar situation and I'm just trying to work out if it's worth attempting to control the UFH through evohome or just have it on "dumb" controls.

Main reason I'm debating this is because none of the new rooms will be in use all or most of the time, so we will only need to heat them when we intend to use them and so having the UFH on dumb controls wouldn't be the end of the world. For rooms in the rest of my house which are and will continue to be used more regularly, the HR92s work really well to give me the control I need.

Anyway, as I understand I would need the following:

1 x HCC80R UFH controller - because I would have multiple UFH zones
3 x wireless room thermostat (DT92 or Y87RF) to monitor temperature in each room

It sounds like the wiring between my boiler and the existing BDR91 relay will need amending to incorporate control of the UFH zones. Is that correct? What exactly needs to be done here?

Also, I don't quite understand the equivalent of the HR92 TRVs in the UFH scenario so would appreciate some clarity on that.

Finally, I know this is an automated home forum but I could do with some advice on whether UFH is really the best solution given my expected usage pattern for the extension space. I'm getting the impression UFH is best where you are using the space regularly or all the time and so the system has plenty of time to heat and then you make use of the lasting effects of that heat as you are using the space a lot. In my case, if I will only ever be heating the rooms on occasion when I intend to use them, maybe I'm better off just putting in good ol fashioned rads!

Help would be much appreciated...TIA!

[gordonb3]

If you are rarely going to use the rooms I'd say wet UFH is a bad choice. It can literally take hours to add like 3 degrees whereas the rads in my children's bedrooms will do that in 10-15 minutes. Electrical UFH would do a lot better job as it sits directly underneath the floor covering and you should feel it almost instantly with e.g. PVC tiles. You could also have a look at wet skirting board heating.

[freddyq]

If you are rarely going to use the rooms I'd say wet UFH is a bad choice. It can literally take hours to add like 3 degrees whereas the rads in my children's bedrooms will do that in 10-15 minutes.

That is exactly my concern to be honest with wet UFH. I just thought maybe if I know it takes time, when I intend to use the room I turn the heating on in advance.

With electric, I've read a lot about it being a) expensive to run and b) not really to be used as primary heating source for larger spaces.

So my gut right now is saying if wet UFH isn't right for me, then just go with rads. I didn't know about the skirting one so thanks for that, I'll check it out.