Extend underfloor heating

mhcork

Hi,
Currently renovating a 4-bed semi and putting down UFH (floors being dug up anyway).
We have plans to build an extension to the side (L-shape) next year so trying to be clever with regards to location of UFH manifold. Boiler will have to be located within existing walls for now but will be relocated to utility room in extension next year.

I know the manifold should be located as centrally as possible but the centre of the house will be in a different place next year than it is today! Ideal location for it today would under the stairs but extension will require 2 or 3 UFH loops so how would I go about plumbing those back to manifold later (new floor/screed will be down in existing house by then)? Another option is to locate manifold and boiler on the wall that will eventually be demolished to link with the extension (approx. centre of house+ext) and maybe allow a bit of 'slack' in UFH loops to make it easier to relocate manifold in the extension (also feed from boiler will be coming from that side).

All of this is based on my understanding that you can only have one UFH manifold - happy to be corrected if that's not the case. Which then lead me to wonder would it not be easier to just treat the extension as a separate building and have a small combi boiler to feed utility/kitchen sinks and UFH manifold for the extension only (with existing boiler serving the main house with its own manifold). Or am I mad?

Has anybody been faced with a similar situation before?
Any advice welcomed.
Thank you.

gummiebear

hi mhcork, very old post I know but did you ever get an answer, what did you do? In same situation.

mhcork

Hi, ended up with 2 manifolds, one installed under stairs of renovated house, once installed later for extension only. Each needed its own pump and UFH wiring board which created a few challenges for the electrician to make sure each pump only came on if/when the corresponding zone required heating. Pumps had to be wired through individual relays and some fiddling around needed to ensure boiler call worked as expected as UFH wiring boards usually designed to work as standalone instead of in pairs.

Bottom line is it's doable.
HTH.

gummiebear

Doable but sounds expensive. The footprint of my future extension exists already in the form of a detached garage (apart from a small few sqm) im wondering if I should do the ground work and attach when i can afford the extension. Hmm, will wait till the quotes come in I guess.

mhcork

Cost of extra pump/manifold/board not that much in overall scheme of things (couple 100s maybe). Electricican cost went up a bit but mostly due to additional lights/sockets/etc. Not sure how much extra he charged me to scratch his head for a few days until he figured it out

One option might be to run ducts now under floor of main house to outside wall facing garage so you can feed UFH loops from extension back to main manifold later. I did this for electrical wiring (CAT6/Coax/MCB feed) but wasn't an option for UFH because of distance and number of loops required.