UFH in half a room vs rads

[stressedouttumbleweed]

Hi,

We're doing an extension soon. Demolishing an old lean to and rebuilding properly. The extension will be 8m x 4m, then we're opening the back of the house to make one large space-approx 6m x 8m (there will be a small part of the new extension walled off to make a utility room.

We have been planning on UFH (wet) but it will only be in the new part of the room (so 6mx 4m) as too expensive to remove floor to retrofit heating. We have an existing 7000BTU vertical rad which will sit at the corner of the old room beside the new area and then the kitchen will be in the other end of the existing room (so no UFH or radiator) we have a plinth heater that works of the CH currently in there which we use fairly rarely.

Will it be enough for the space to just have the UFH in one part or would it be weird. Should we forget about UFH and just have rads in the new part (& how many/how big would they need to be)

Also slight concern we were talking to the builder about another job they'd done and the people were complaining the UFH had cold spots and were told it was because they had the UFH set too low and it needed to be up around 26-28 to ensure the thermostat didn't cut off too soon to make sure all the floor was warm? This doesn't sound right to us so just a little worried in case they haven't installed it brilliantly!

We have recently moved into a house with a space similar to what you describe; in that the previous owners did an extension and created a utility, kitchen diner and a family space.
So we have wet UFH in the kitchen diner space (manifold is in the utility) through into the extension where the kitchen diner is. The family space is in the original part of the house and has a radiator. Our UFH is under screed so we have no hot/cold spots as the screed warms up across the whole floor. If you have tiles in the original part of your house then you will feel the difference as you walk off the UFH area. We have engineered wood in our original part so we don't really notice the difference too much. It hasn't been weird for us to have the mix of the 2 in one space but I think it depends on how cold that part of the house is without the extension. Ours faces south so it is warmer anyway than the rest of the house. Not sure if that helps you.

It faces east planning on french doors and a window plus a couple of skylights so will hopefully be warmed a bit from the morning sun, it's currently freezing but that is because it is open to a very old conservatory which is being demolished for the extension, we're hoping it will make a huge difference to how warm the house is.

Flooring is going to be LVT throughout and the system will be under latex screed so it should all warm up-my worries are they have done something wrong with the installation in the other place!

OP, I'm looking to do almost exactly the same work as you. Removing a sun room/conservatory and replacing with an extension, same dimensions as yours. Also thinking of doing the same with UFH just in the new part.

Would you mind sharing the quote you've had and whereabouts in the country you are? Prices have shot up so much I'm just trying to work out if it's feasible before I commit myself and spend out on plans!

We're near the suffolk/cambs border and we're expecting to pay around £95k including everything bar decorating. Original ball park quote 18mo ago was £60k (without kitchen and knock through) so prices have def shot up!

We're doing it under PD though, we're detached and not in conservation area so have had no architect involvement, our builder has done the plans

Would it really be that expensive to extend ufh to the old part of your kitchen? Most ufh systems don't need a full screed, just a couple of mm levelling compound and adhesive to put tiles on top. You'd need to remove your current floor covering anyway and bring up the floor to the same level, I'd just extend ufh to the whole room before you install your kitchen and new flooring and regret it. I fear if your ufh is only for half a room, the heat will disappear and the room will never come up to temperature, or you will have to run the radiator and plinth heater 24 hours in tank with the ufh, but that's super ineffective and will be very expensive.

Thank you! That's actually better than I was expecting. I expected about 70k pre covid for my area (Greater London) but I was worried I was looking at closer to 120k now, without kitchen... and I just don't think I can justify that amount for a want, rather than a need. Perhaps I'll take the plunge!

Good luck with your build.

We're looking at a wet UFH system and existing floor is concrete so we'd be looking at adding(or removing) 10-15cm height according to builder, not just a couple of mm? It's just not in budget tbh and we wouldn't want that height difference into the other rooms and staircase