Underfloor heating install during extension

[CIS121]

I'm getting an extension done shortly and am considering the extra cost and benefits of UF heating run from the GCH, but only in the new build sitting room.

As I understand it needs an extra thermostat to control it, a motorised valve and lots of plastic pipe laid in runs. The builder says his plumber will probably charge about £1k for materials and labour.

Has anyone had it installed and got any advice like if it's really worth it?

[caziques]

You will need to allow 5 metres of pipe per sqm of floor area, 1216 Pex pipe should cost no more than a pound a metre. No more than 25sqm of floor area for one run of pipe, so more than this and you'll need two runs.

You will need a tempering valve as the maximum temperature of the water in a concrete floor is 45c.

Should you do it? Yes. Next question.

[Arthur Jackson]

Make sure you get a flow and return to the system, NOT just tacked onto the radiator circuit.

[CIS121]

Arthur Jackson said:

Make sure you get a flow and return to the system, NOT just tacked onto the radiator circuit.

Does a flow and return system mean it's got it's own supply feed from the boiler separate from the GCH, so it can come on independently?

[Arthur Jackson]

Yes, it's very important. Because of how it works it needs to be on for different times. Radiators pump out lots of heat quickly, a heated slab needs longer at lower temperatures.

[-Z-]

We've just had it put in with our garage conversion, well worth it, esp in a large open space like ours.

Your quote sounds a bit expensive possibly? The bits in a kit cost £450 for a 20sqm room from here: http://www.theunderfloorheatingstore-onlineshop.co...

I bought it and my builder installed it, think he charged around £200-300. Direct connection to the boiler, so no motorised valve needed. You didn't mention needing a pump, which you definitely do.

Oh and make sure you get an electronic pro thermostat, so you can set to come on before the rads, due to needing extra time to get heated up.