DIY UFH install from below the floor?

[kjacko]

Hi all,
I have cut out a doorway downstairs that leads to the “cellar” which open up the space below the rest of the house and runs all the way under the living room, kitchen and bedrooms.
When we walk on the floor we can feel the heat from some of the pipes that are just below the floorboards. As i have easy access to the underfloors for these rooms and i can see all the radiator pipework, i’m wondering whether i could extend the pipework and create a UFH system, almost like an extension to the rads, or a replacement. We have a 12kw ASHP, which was installed by the previous owner in October 2023 which needs to be taken into consideration for sizing(?)
The cellar seems to maintain constant ambient temperature and whilst we haven’t experienced a winter here yet (west Wales) i dont think it will get so cold that insulation would need to be considered in the cellar, when laying extra pipework.

Would appreciate your thoughts regarding this. We will be removing all existing floor coverings to secure all floorboards as they squeak and are a bit springy, not that it matters I guess as the pipes will be installed from underneath the floorboards.

Anyway TIA for any comments and/or advice.

 

[steven lee]

That access underneath is a big advantage, and it can work, but I would not just tee off the radiator pipework and hope for the best. Underfloor needs its own low temperature circuit and manifold, because an ASHP runs happiest at lower flow temperatures than radiators. Put insulation and spreader plates under the pipes so most of the heat goes up through the floorboards instead of warming the cellar. Before you commit, get a heat loss figure for those rooms and check the 12kW unit still has headroom, because a cold snap will show up any shortfall fast.

 

[Madrab]

Given you have a ASHP then that system is ideally suited for UFH, that being said it would all depend on what system you have and what temps it's designed to run at.

The current system output should be sized to the Heat Loss of the building/rooms and would hope it has been sized for the current rad loads and output. Adding an extra system of heat emission - UFH - would no doubt take it over it's limit. That being said the rads could be removed allowing the output of the system to solely be run as UFH.

As to your original question, unfortunately no - it wouldn't be as simple as just adding extra pipework in under the floor