Overlay UFH system

[anoncamb]

Hi,

We are currently doing an extension and thinking of having wet UFH in the extension and in existing living room. The existing rooms don’t have floor insulation. Overlay UFH is the only option as we can’t increase the floor height too much.
I hear conflicting views about having UFH on uninsulated concrete slab and screed. Some say that there will be heat loss through the ground. Some day that overlay systems have a foil which prevents the heat from travelling down.

Has anyone tried retrofitting an overlay wet UFH? Could you please share your experience?

[Wishiwasatailor]

Had this put in a couple of days ago over an area of concrete and the suspended floors. Too early to have a definitive answer but it does feel warmer throughout

[Diyextension]

There has got to be heat loss through the ground if there is no insulation to stop it ? The whole idea of it is that the floor (screed ) acts as one big heat sink and releases the heat into the room, the heat can’t go down because of the insulation stopping it, so it goes up.

it will work to an extent but it’s will be less efficient ( costly to run ).

Is not taking up the floor and adding insulation an option ?

[Sunflowergirl1]

We had a new extension and had standard UFH which is great. Installer wouldn't do overlay in an existing part due to lack of insulation....said all we would do is heat the earth and be cold.

The new area is lovely but crikey, it is well insulated

[anoncamb]

@Diyextension - There is only 20mm of screed after which we hit the concrete. So we will have to dig the concrete in the whole area.

[coolmum123]

In my old house we renovated and had wet UFH through the old part of the house and then under concrete in the new bit. We had the same issue but what our builders did in the existing bit was they pulled up the floor boards and then attached netting between the floor joists and then put insulation in the netting then they laid this flooring down with tracks in it for the UFH pipes to sit in so the floor level is unchanged. Whilst this doesn't completely eliminate heat loss it does reduce it as afterwards we didn't feel a big difference in room temperature between the old and the new bit.

[anoncamb]

@coolmum123 - Thanks for providing the info. I guess yours was a suspended timber floor. Ours is concrete and hence cannot do what you have done.

[coolmum123]

@anoncamb sorry I misread your initial post. Would it be worth contacting can underfloor heating specialist and discuss? I know there is now heating systems that go into skirting boards and walls so there might be solutions the builders don't know about?