Underfloor heating in a new extension

Dear All,

Any advice or comments on the following plan?

I want to build extensions to the kitchen and dining room parts of a linked kitchen-diner. I am contemplating having under-floor heating in the new pa rts - a total area if around 12m2. - but not retrofitted to the existing fl oor. I am assuming this will remove the need for new radiators

I want to replace the floor - currently laminate on top of concrete - with tiles in the kitchen, and engineered wood in the dining room.

I am hoping to keep the existing boiler ( a 10-yr old 18kw condensing boile r). The house is a bog-standard 3-bed 60s semi with cavity wall insulation.

Any pitfalls, things to be wary of?

Thanks.

Chris

Reply to
cskrimshire
Loading thread data ...

If it's installed at build time, it'll be fine. You're wise not to try to retro-fit it to existing floors.

You'll need a separate heating zone for the UFH and will need somewhere to install a mixing valve (to control the UFH water temperature to a lower lever than the rest of the system) and a dedicated pump. An additional zone is easiest to achieve if you already have an S-Plan system.

You'll need to design the floor correctly to get the same level as the existing floor after allowing for concrete slab, rigid foam insulation, and screed over the UFH pipes.

You'll need to do the heat loss calculations to make sure that the UFH will deliver sufficient heat to the new area but, since everything will need to be built to current thermal efficiency standards, you shouldn't have any trouble.

We converted a built-in garage into a kitchen a few years ago and installed UFH in that in the way described above. The concrete slab was already there and we only had about 150mm for the insulation, screed and ceramic floor tiles - which was a bit tight, but it all works like a dream. Because the floor is radiating, the kitchen feels comfortable at a lower air temperature than the rest of the house.

Reply to
Roger Mills

ed kitchen-diner. I am contemplating having under-floor heating in the new parts - a total area if around 12m2. - but not retrofitted to the existing floor. I am assuming this will remove the need for new radiators

h tiles in the kitchen, and engineered wood in the dining room.

ler). The house is a bog-standard 3-bed 60s semi with cavity wall insulatio n.

Roger,

Thanks for this.

Would the pump/valve be about the same size as normal pumps/valves?

And where should they go ideally? Space is a bit tight in the airing cupboa rd, which would be my first guess, on grounds of having the pump noise away from living areas. However, the boiler will be sited in the new kitchen - very close to the UFH floors.

Chris

Reply to
cskrimshire

The pump would be very similar to a normal CH pump, if not identical. The UFH valve is a mechanical blending valve[1] - similar to the valves used to feed the hot taps in sheltered accommodation, to stop people from getting scalded. [You also need a zone valve, of course, which is the same as your existing zone valves, assuming you've got an S-Plan system. This needs to be controlled by a room stat located in the area heated by the UFH.]

The pump and blending valve need to go very close to the start and end of the UFH pipework. The zone valve needs to go at the point where your system splits into zones - probably in the airing cupboard if that's where the existing zone valves are. You then need a hot feed from the zone valve down to the UFH system, and a return to the boiler.

When we did our kitchen conversion, we moved the doorway into the kitchen and needed to brick up the old one, which was in a cavity wall. This provided the opportunity to create a little chamber in the leaf on the kitchen side, to accommodate the pump and valve. This has a plywood cover which is flush with the rest of the wall, so everything is hidden. It also happens to be right next to the boiler - so the return route is very short. [The supply route is a lot longer because the water has to go all the way up the airing cupboard - where the main pump and zone valves are located, and all the way back].

[1] The principle of operation is that the water circulating round the UFH is much cooler than that going to the radiators - typically 40 degrees rather than 75-ish. This is achieved by blending hot water from the boiler with the cool water return from the UFH and then sending that round. The valve is purely mechanical - like a shower mixing valve - and thermostatically adjusts the relative proportion of new and return water in order to achieve the desired flow temperature. The main (existing) pump delivers hot water to the UFH zone - in the same way as it does to the other zones - and the UFH pump simply circulated the water through the UFH pipes.
Reply to
Roger Mills

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.