Zoning means dividing a heating system into areas that can be controlled independently. Each zone gets its own thermostat, and each responds only to what that part of the building actually needs.
The appeal is obvious enough. You heat the rooms in use rather than the whole building, and different occupants get different temperatures without arguing about it. What is less obvious is how many zones to create, where to draw the boundaries, and what constrains those decisions once the floor is down.
How Zoning Works
The mechanism differs between electric and hydronic systems, though the principle is the same.
Electric systems
Zoning in an electric system is achieved through individual thermostats, one per area. Each thermostat switches its own heating circuit, and the circuits are electrically independent of each other.
This makes electric zoning straightforward. Separate cable runs go in for each zone during installation, each connects to its own thermostat, and that is essentially the whole arrangement. For a bathroom, a small extension, or a single-room retrofit, it is hard to beat for simplicity.
Smart thermostats extend it further, allowing schedules per zone and control from an app.
Hydronic systems
Water-based zoning uses valves rather than switches, which makes it more involved but also more capable.
A manifold sits at the centre of it. Warm water arrives from the heat source and the manifold divides it between individual loops, one per zone. Each manifold branch carries a valve, and on top of that valve sits a thermal actuator.
When a zone’s thermostat calls for heat, the actuator opens that branch. Water flows into that loop and nowhere else. Once the room reaches temperature, the thermostat stops calling, the actuator closes, and the loop shuts off.
One detail catches out installers new to these. Thermal actuators take three to five minutes to open or close, because they work by warming a wax element rather than driving a motor. That is deliberate: the gradual movement avoids the water hammer a fast-acting solenoid would create in a building where valves are opening and closing all day.
The Control Chain
In a hydronic system, four components have to work together. Understanding the sequence explains most of what goes wrong.
The thermostat measures its room and produces a demand signal. It does not move water. It only says whether heat is wanted.
The base station receives signals from every thermostat in the building and coordinates the response. It powers the correct actuators, and it also signals the heat source, so the boiler or heat pump runs when a zone genuinely calls rather than firing regardless.
That second function matters more than it sounds. Without a base station tying the zones together, you can end up with a heat source running while every zone valve is closed, which achieves nothing and wastes a great deal.
The thermal actuator opens the manifold branch for that zone.
The manifold distributes flow, with a flow meter on each branch so the circuits can be balanced.
Specify the chain together, not the thermostat alone. A thermostat is only as useful as what it can drive. If its output cannot power the number of actuators on a large zone, that zone will not open. If its voltage does not match the wiring centre, it will not integrate at all. These are the most common zoning failures, and they are entirely avoidable at specification stage.
How Many Zones?
This is the question people actually have, and general advice rarely answers it.
The useful rule is to create a zone wherever a room genuinely needs a different temperature or a different schedule from its neighbours. Not wherever there happens to be a door.
Rooms that usually justify their own zone
Bedrooms, because most people sleep better cooler and because they are unoccupied all day. Bathrooms, because they want to be warmer and because occupancy is brief. Kitchens, because cooking generates substantial heat of its own and a kitchen frequently needs less heating than the room next to it. And any room with markedly different exposure, such as one with large north-facing glazing.
Rooms that often do not
Adjacent spaces used at the same times, at the same temperature, by the same people. A hallway and a landing rarely need separate control. Two reception rooms that are always both occupied in the evening can share.
Each additional zone costs an actuator, a thermostat, wiring, and a manifold branch. Where it delivers no behavioural difference, it is expenditure without return.
Where large rooms need dividing
Sometimes a single room needs more than one zone, and the reason is not comfort preference but physics.
An irregularly shaped room, or a long open-plan space, may not heat evenly from one circuit. Perimeter areas near external walls lose more heat than the middle of the room. Dividing such a space allows the perimeter to be served separately, frequently with tighter pipe spacing as well.
The Constraint Nobody Mentions: Loop Length
Zone boundaries are not purely a matter of preference. They are constrained by how long a single loop of pipe can run.
Water entering a loop loses heat along its path. By the time it returns to the manifold it is cooler, and if the loop is too long, the far end of the circuit delivers noticeably less heat than the start. The floor is warm near the manifold and lukewarm at the far end.
Maximum loop length depends on pipe diameter, spacing, and flow rate, and the manufacturer’s figures should be used rather than a general rule. What matters for zoning is the consequence: a large area may need several loops even if it is a single zone.
Those loops all open and close together, driven by one thermostat. But the thermostat has to be able to power multiple actuators, which brings us back to specification. Most standard thermostats drive one. A large open-plan zone served by four or five loops needs a thermostat rated for that, or it simply will not open properly.
Preparing a Zoning Plan
Purpose of each zone
Know why each division exists before drawing it. Zones based on room function work well: bedrooms, living areas, bathrooms, kitchens. Zones based on nothing in particular tend to produce cost without benefit.
Larger rooms may need several zones for even distribution, and so may rooms with very different levels of external exposure.
Room layout and shape
Even heat distribution is the objective. Irregularly shaped rooms and open-plan spaces frequently need more than one zone to achieve it, and high-traffic areas may warrant separate treatment.
Thermostat placement
Each zone needs a room thermostat, and where it goes affects accuracy more than most people expect.
Mount it on an interior wall at roughly 1.5 metres from the floor. Keep it away from direct sunlight, which makes it read warm and shut the heating off while the room is still cold. Keep it away from draughts near exterior doors and windows, which make it read cold and overheat the room. And away from heat sources, so lamps, televisions, and radiators.
A thermostat in the wrong position produces a zone that never quite behaves, and no amount of correct specification elsewhere fixes it.
Floor covering per zone
Worth checking at planning stage, because it is easy to miss. Different rooms frequently get different floor coverings, and covering determines how much heat reaches the room.
Tile conducts readily. Timber and vinyl insulate more and require higher water temperature for the same output, and they impose their own surface temperature limit, commonly around 27°C. Carpet with thick underlay can reduce output substantially.
Since all zones typically share one flow temperature from the mixing valve, a zone with a highly resistant covering may underperform against neighbours running the same water temperature. Either accept it, tighten the pipe spacing in that zone, or reconsider the covering.
Flow and balancing
Loop lengths differ between zones, and the shorter circuit offers less resistance. Without correction it takes a disproportionate share of the flow while the long one is starved.
Manifold configuration must account for this. Each branch is adjusted so every loop receives the flow its length and heat demand require, and this is a commissioning task rather than a design one. Skip it and you get the familiar complaint: some rooms comfortable, others never quite reaching temperature, with the system apparently running normally throughout.
What Zoning Actually Saves
Being honest about this is more useful than a vague efficiency claim.
The saving comes from not heating unoccupied space, and its size depends entirely on how much unoccupied space you have and for how long.
A family home where bedrooms sit empty from eight in the morning until evening has substantial unheated hours available. An apartment occupied continuously by someone working from home has considerably less to gain.
Two further points are worth making.
Zoning generally saves more than scheduling does in a multi-room property. Turning the whole house down for a few hours removes less waste than never heating three rooms at all.
Unheated rooms are not free of heat. Heat moves through walls and floors from warm rooms into cool ones, so a zone set well below its neighbours receives some warmth regardless. The saving is real but smaller than a simple calculation suggests.
Scheduling in a Zoned System
Underfloor heating responds slowly. That is its nature, and it changes how zoning should be operated.
The screed holds substantial thermal mass, so a floor takes one to two hours to warm and continues releasing heat after the system stops. Apply a deep setback to a zone and you get the worst of both: the floor is still warming when you want it warm, then still giving off heat after you no longer need it.
Modest setbacks of a degree or two work better than aggressive ones. Let the thermal mass work with the schedule rather than against it.
There is an exception. A zone that is genuinely unoccupied for a long period, such as a guest bedroom, can be set well back or off entirely, because there is no recovery deadline to miss.
Common Zoning Mistakes
| Mistake | Consequence |
|---|---|
| Too many zones | Cost without behavioural benefit |
| Too few in a large open space | Uneven heating, cool perimeter |
| Thermostat capacity too low | Zone never opens reliably |
| No base station coordination | Heat source runs with all valves closed |
| Loops not balanced | Some rooms warm, others never reach target |
| Thermostat badly placed | Zone reads wrong and misbehaves permanently |
| Manifold branches unlabelled | Every future service visit starts with guesswork |
| Aggressive setbacks on high mass floors | Poor comfort with little saving |
The last two deserve a word each.
Label the manifold branches at installation. It takes a few minutes with a marker and a printed schedule. Years later, identifying which of twelve branches serves the back bedroom is otherwise a process of opening one valve and walking around the house.
Record the commissioning settings. Flow temperature, balanced flow rates, and which thermostat drives which branch. Without that reference there is nothing to measure drift against, and drift in a mixing valve changes performance with no visible symptom at all.
Zoning with a Heat Pump
One interaction is worth understanding, because it is counterintuitive.
A heat pump modulates its output to match demand, and it runs most efficiently when it can settle into steady operation. Zoning reduces demand, which is the point. But if too many zones close at once, demand can fall below what the heat pump can modulate down to, and it starts cycling.
Two things address this.
A differential pressure bypass valve gives the circulation pump a path when zone valves close, protecting it from working against a closed circuit.
And correct heat pump sizing matters more in a zoned system than an unzoned one, because the minimum modulated output has to suit not just the building’s mild-weather demand but the reduced demand when several zones are satisfied.
This is not an argument against zoning. It is an argument for considering the zone plan and the heat source together rather than as separate decisions.
Electric or Hydronic for Zoning?
Short version: electric zoning is simpler, hydronic zoning is cheaper to run.
Electric zones are electrically independent, so adding one is straightforward and the control is simple. Installation costs less and the floor build-up is minimal.
Hydronic zoning needs a manifold, actuators, and coordination, which is more involved. In return, running cost is substantially lower, particularly with a heat pump, because the heat source delivers three to four units of heat per unit of electricity rather than one.
For a bathroom or a single room, electric usually wins. For whole-house or commercial zoning, hydronic does. Our comparison of electric and hydronic underfloor heating covers the wider decision.
“People tend to ask how many zones they should have, and I think the better question is which rooms they actually want to behave differently. If two rooms are always occupied at the same time by the same people at the same temperature, a second thermostat achieves nothing except another component to fail. Where zoning earns its money is bedrooms, because they sit empty all day, and bathrooms, because they want to be warmer for twenty minutes rather than all afternoon. Beyond that, be sceptical. Every zone is an actuator, a thermostat, a manifold branch, and a bit more wiring.”
— Maggie Shen, Director of Legom
Components for a Zoned System
Legom manufactures the complete zoning chain at its facility in Jiaxing, Zhejiang Province, supplying partners in more than 90 countries.
Manifolds with a flow meter on each branch, which is what makes balancing possible.
Thermal actuators across eleven models, in normally closed and normally open configurations, from 12V to 230V, with M30×1.5 and M28×1.5 thread options. Manual override models with a position indicator are useful in larger installations, since a technician can confirm valve state visually rather than by measurement.
Room thermostats in four models. The Apus RT-A1 drives up to five actuators simultaneously, which suits large or open-plan zones served by several loops. The RT-X1 Ascent offers 7-day programming with six periods per day. The FC FC1D is the model with an automatic changeover terminal for reversible heating and cooling systems.
Base stations to coordinate demand across zones and signal the heat source.
Floor heating pipe with oxygen barrier protection to DIN 4726, which prevents oxygen diffusing into the water and corroding pumps and valves elsewhere in the system.
Because the components are produced together, compatibility is designed in rather than assumed. That removes an entire category of zoning problem, since voltage and output mismatches between thermostat and actuator are among the most common failures. OEM and ODM services are available across the range.
Frequently Asked Questions
How many underfloor heating zones do I need?
Create a zone wherever a room genuinely needs a different temperature or schedule from its neighbours. Bedrooms usually justify one, since they sit empty all day and most people sleep cooler. Bathrooms do, since they want to be warmer briefly. Kitchens often do, because cooking generates its own heat. Adjacent rooms used at the same times by the same people at the same temperature generally do not, and each unnecessary zone costs an actuator, thermostat, wiring, and manifold branch for no behavioural benefit.
Does zoning save energy?
Yes, and in a multi-room property it usually saves more than scheduling does, because never heating three rooms removes more waste than turning the whole house down for a few hours. How much depends entirely on how much unoccupied space you have and for how long. One qualification: unheated rooms are not free of heat, since warmth moves through walls and floors from adjacent zones, so the saving is real but smaller than a simple calculation suggests.
Can one thermostat control several loops?
It can, but only if its output capacity allows. A large room frequently needs several loops because a single circuit would exceed the maximum practical pipe length, and all those loops open together on one thermostat signal. Most standard thermostats drive one actuator. A zone served by four or five loops needs a thermostat rated for that, such as a model driving up to five, or the zone will not open reliably.
Why does a large room sometimes need several zones?
Two reasons. Loop length is limited, since water loses heat along its path and an over-long circuit delivers noticeably less at the far end, so a large area may need several loops regardless of how it is controlled. And perimeter areas near external walls lose more heat than the middle of a room, so dividing a long or irregular space allows the perimeter to be served separately, frequently with tighter pipe spacing as well.
Where should zone thermostats be placed?
On an interior wall roughly 1.5 metres from the floor, in a position representative of the room. Keep them out of direct sunlight, which makes them read warm and shut the heating off while the room is still cold. Keep them away from draughts near exterior doors and windows, which produce the opposite error. And away from lamps, televisions, and other heat sources. A badly placed thermostat produces a zone that never behaves correctly regardless of how well everything else is specified.
Should I use deep setbacks on zoned underfloor heating?
Generally no. Underfloor heating takes one to two hours to respond because of the thermal mass in the screed, and it continues releasing heat after the system stops. A deep setback means the floor is still warming when you want it warm and still giving off heat when you no longer need it. Modest setbacks of a degree or two work better. The exception is a zone genuinely unoccupied for a long period, such as a guest room, where there is no recovery deadline.
What does a base station do in a zoned system?
It receives demand signals from every thermostat and coordinates the response, powering the correct actuators and signalling the heat source. That second function is easy to overlook and matters considerably: without coordination, a heat source can run while every zone valve is closed, which achieves nothing and wastes a great deal. In a multi-zone installation the base station is what turns individual room controls into a system.
Does zoning affect heat pump operation?
It can, and the interaction is worth planning for. A heat pump runs most efficiently when it settles into steady modulated operation. If several zones close at once, demand may fall below the unit’s minimum modulated output and it starts cycling. A differential pressure bypass valve protects the circulation pump when valves close, and correct heat pump sizing matters more in a zoned system than an unzoned one. Consider the zone plan and heat source together rather than separately.
Reviewed by Maggie Shen, Director at Legom, on October 1, 2026. This guide to underfloor heating zones was reviewed for technical accuracy, including loop length constraints on zone design, thermostat output capacity requirements, and the interaction between zoning and heat pump modulation.