Full UFH Installation — Hampstead Extension

Extensions in Hampstead are never simple. The planning, the heritage considerations, the expectation that every finish will be exceptional — and then the mechanical and electrical design that has to sit invisibly beneath all of it.

This project was a full-width rear extension to a Victorian detached property: open-plan kitchen, dining and living space totalling approximately 120m², with bi-fold doors opening onto a south-facing garden. The architect had specified wet underfloor heating throughout the extension — partly for comfort, partly because the open-plan design left no natural wall space for radiators that wouldn't compromise the aesthetic.

RARE were brought in at design stage, which is exactly when you want your heating engineer involved. The first question was whether the existing boiler — a Vaillant ecoTEC Plus 30kW combi, installed four years prior — had the capacity to serve the additional UFH load on top of the existing radiator circuit on the upper floors. The second question was floor depth: the architect had specified a particular floor finish that left very little tolerance, and every millimetre of system depth mattered. The third question was control: the property already had a Heatmiser NeoHub managing the upper floor radiators, and the client was insistent that the extension's heating would be managed through the same app, not a second separate system.

RARE's heat loss calculation for the extension confirmed what the team had expected: the Vaillant 30kW, sized correctly for the original house, had just sufficient capacity for the additional UFH load — but only just, and only with careful system design to keep flow temperatures optimised for the boiler's condensing efficiency.

An 8-zone manifold was specified and located in a purpose-built utility cupboard at the edge of the extension — accessible but invisible from the living space. The overlay system selected was an 18mm low-profile pipe-and-board product, keeping the total floor build-up within the architect's tolerance. Pipe spacing was calculated zone by zone based on room dimensions, floor finish thermal resistance and the target output at the agreed flow temperature.

Over four days, RARE installed the complete system alongside the main contractor, coordinating closely with the site manager to ensure the UFH was pressure-tested and signed off before any floor screed was laid. The new 8-zone manifold was wired back to the existing Heatmiser NeoHub — which accepted the additional zones without any hardware changes — and 8 new NeoStat thermostats were installed. When the client opened the NeoHub app on her phone for the first time, she could see all 12 zones of her property: the original 4 upstairs and all 8 zones of the new extension, each independently controllable.

Full documentation — including the pressure test certificate, zone layout drawings and commissioning report — was provided to the architect for building control sign-off.