Zoning approaches — wireless TRV vs wired multi-zone
Two main approaches. (1) Wireless smart TRVs: replace existing thermostatic radiator valves with smart TRVs that communicate to central hub (Tado X, Hive Radiator Valve, Drayton Wiser). Cost £55–£140 per TRV + £85–£180 hub. Whole-house 12-radiator install £750–£1,800. Pros: no wiring, easy retrofit, per-radiator zone control. Cons: TRVs only restrict flow at the radiator (boiler still fires for any single zone calling); modest savings without boiler interlock. Best with TPI-compatible boilers and Opentherm thermostat. (2) Wired multi-zone with motorised valves: each zone has dedicated thermostat + motorised valve + boiler interlock. Honeywell evohome (6–12 zones £950–£1,800), Heatmiser Neostat (UFH + radiator mixed). Boiler fires only when a zone calls — significant energy savings. Cons: requires rewiring (often 8–12 days of disruption), more complex install. Best for whole-house renovations where walls are open.
Smart thermostats and the boiler conversation
Modern smart thermostats (Nest 3rd Gen, Hive Active Heating, Tado Wireless, Drayton Wiser) replace single-zone thermostat at £140–£280. Features: app control, schedule learning, geofencing, weather compensation. The critical question is whether the thermostat talks to the boiler via Opentherm/eBus (modulating, efficient) or just on/off (legacy boiler interlock). Modulating control: boiler ramps output up/down to match heat demand — 8–15% efficiency gain over on/off control. Most condensing boilers from 2015+ support Opentherm; older boilers don't. If retrofitting smart thermostat to old boiler, accept on/off control. Multi-room thermostat support: evohome, Heatmiser, Tado X — each thermostat is a zone, all communicate to single boiler. Single-thermostat systems (basic Nest, Hive, Drayton Wiser) only control whole house — pair with smart TRVs for room-level zoning. Choose based on house size and budget: small flat = single Nest; 4-bed house = evohome multi-zone.
UFH + radiator hybrid zoning
Common in renovations: wet UFH on ground floor (open-plan kitchen + family room) + radiators upstairs (bedrooms). Two control systems must coordinate — UFH at 35–45°C flow, radiators at 55–65°C. Heatmiser NeoHub + NeoStats handles both natively: single app, UFH manifold actuators + smart radiator valves + boiler interlock. Cost £450–£950 for UFH manifold control (6 zones) + £55–£140 per radiator smart TRV. Alternative: separate UFH controller (Polypipe, Wunda) + separate radiator system (Tado, Hive) — works but two apps and no shared scheduling. Single integrated control strongly preferred. Heat pumps: UFH at 35–40°C; radiators upstairs at 45–55°C — same control approach works, just lower flow temperatures. Specify multi-zone control to manufacturer at design stage; retrofit is more expensive than first-fit.
Commissioning, balancing and energy savings
Zoning hardware is half the job — balancing and commissioning deliver the savings. Hydraulic balancing: adjust lockshield valves on each radiator so flow matches design output; un-balanced systems deliver 30–50% of intended room temperature in distant radiators. Commissioning cost £180–£420 for 12-radiator house. Set-back schedules: zones used 8 hours/day (home office, dining room) run at 16°C when unused vs 21°C when occupied — save 18–28% heating energy. Geofencing: thermostat reduces all zones when residents leave house, returns to comfort 30 minutes before re-entry — save 8–15%. Total realistic savings from full zoning + commissioning + smart scheduling: 15–25% of annual heating bill = £180–£420/year on a typical London house. Payback 3–8 years on £950–£1,800 install. Bonus: zoning extends boiler/heat-pump lifespan by reducing cycling.
