Smart thermostats for underfloor heating: what to look for

A smart thermostat lets you change the heating from your phone, set schedules for each room and, on better models, start the heating early so a room is warm at the time you asked for. With radiators, many homes get by with one smart thermostat in the hall. Underfloor heating is different. Every room has its own loops and actuators on the manifold, so every room needs its own thermostat to tell the wiring centre when to open them.

This guide explains what makes a thermostat "smart" in UK rules, what features matter for a heated floor, whether a hub or WiFi thermostat is better value, and which model suits which system. It uses Heatmiser's datasheets, BEAMA's controls guides and government research. For the basics of wired and wireless control, see UFH thermostats explained.

What makes a thermostat "smart"?

In UK rules, a smart thermostat does more than offer an app. The Boiler Plus requirements in England, introduced in 2018 for gas combi boiler installs, list a smart thermostat with automation and optimisation as one of four energy-saving options. BEAMA's Part L guidance sets out what that means.

• Time and temperature control combined in one device.
• Automatic adjustment of the settings it uses.
• Optimum start: it starts the heating at the right time to reach the set temperature when you want it.
• Remote adjustment, usually by app.

BEAMA adds that for the best savings, a smart thermostat should also have load or weather compensation, which varies the flow temperature rather than only switching the heat on and off. That is something your boiler or heat pump has to support as well.

An app on its own is remote control. It is useful, but it is the scheduling, optimum start and setback that change how much energy you use.

Do smart thermostats save energy on underfloor heating?

They can, but the evidence is weaker than the marketing. A 2014 government review of heating controls by the Department of Energy and Climate Change found no consistent and reliable body of evidence on how much heating controls save. It noted that most studies were small and from outside the UK, and that people often use controls for comfort rather than saving energy.

What a smart thermostat does well is make good habits easy:

• Room schedules. Bedrooms, guest rooms and a home office can each run at their own times and temperatures.
• Setback. BEAMA's underfloor heating controls guide says floors with high thermal mass, such as screed deeper than 65mm, need a night setback that lets the room cool by about 3°C. A programmable thermostat does that for you.
• Holiday mode and frost protection. The floor holds a low temperature while you are away, rather than staying at comfort level or going stone cold.
• Remote changes. If you come home early or go away unexpectedly, you can change it from your phone.

The Energy Saving Trust, quoted by Which?, calls it a complete myth that it is cheaper to leave conventional heating on low all day. A slow screed floor is a special case, and our guide to UFH warm-up times explains why.

Do I need a smart thermostat in every room?

Yes, in most cases. BEAMA's underfloor heating controls guide says each room must have its own room thermostat or sensor. It allows one thermostat to serve two rooms with a similar use, such as a kitchen and utility, but says bedrooms and en-suites each need their own.

Building Regulations point the same way. BEAMA's summary of Approved Document L, for work in England from 15 June 2022, says each room should have thermostatic control when a heat source is replaced. There are limited exceptions, such as a single-storey open-plan home where the living area is more than 70% of the floor area.

This is why a single "whole-home" smart thermostat designed to switch a boiler cannot run underfloor heating on its own. It has no way to open the actuators room by room. You need a thermostat in each zone, wired or paired to a wiring centre, and the wiring centre fires the boiler or heat pump.

What features should a smart UFH thermostat have?

Look for these, and check the settings ranges in the datasheet. Here is what Heatmiser's neoStat V3 datasheet gives, as an example of a full-featured UFH thermostat.

Feature	Why it matters for UFH	neoStat V3 setting
Floor probe input	Protects wood, vinyl and LVT, and is needed for electric mats	Floor only, air only or air plus floor
Floor temperature limit	Stops the floor going over the flooring maker's maximum	20 to 45°C, default 28°C
Optimum start	Starts early so a slow floor is warm on time	Up to 5 hours, default off
Temperature hold	Keeps a temperature for a set time without changing the schedule	Yes
Holiday mode	Holds frost level while you are away	Yes
Frost protection	Keeps the building from getting too cold	7 to 17°C, default 12°C
Program modes	Choose how flexible the schedule is	Non-programmable, weekday/weekend, 7-day, 24-hour
Override limit and keylock	Stops guests or tenants turning it right up	0 to 10°C limit, keylock
Mesh networking	Each thermostat relays the signal, extending range	Yes

The floor limit default of 28°C is a starting point. BEAMA gives 27°C as an example maximum for some vinyl floors. Set the limit to your flooring maker's figure, and read our guide to floor probes and air sensing for where the probe goes.

Hub or WiFi thermostat: which is better value?

For five or more rooms, a hub with standard smart thermostats is usually cheaper. For one to four rooms, WiFi thermostats that connect straight to your router avoid the cost of the hub.

The Heatmiser neoHub G3 plugs into your router by Ethernet and links up to 32 neo devices. Heatmiser lists Alexa, Google Home, Apple Home and IFTTT support. The neoStat WiFi connects to 2.4GHz WiFi and pairs to the app without a hub.

The wiring centre and actuators are the same either way. The hub also lets battery neoAir thermostats, a neoStat-e for an electric floor and a hot water programmer all sit in one app. For set-up help, see neoHub with Alexa and Google.

Which smart thermostat suits which system?

Match the thermostat to how it reaches the wiring centre and to what it switches.

System	Thermostat	Wiring centre
Water UFH, new build or cables run	neoStat V3 230V	UH4 or UH8
Water UFH, finished rooms, no cables	neoAir battery wireless	UH8-RF
Water UFH, low-voltage network	neoStat 12V	UH8-N
Electric mats or cable	neoStat-e, 16A	None, switches the mat directly
Hot water	neoStat-HW	Cylinder valve

Heatmiser's neoAir FAQ says its batteries last 10 to 12 months in normal use, and a low battery warning shows on the thermostat and in the app. For a side-by-side look at the models, see neoStat vs neoAir vs Slimline.

How should a smart thermostat work with a heat pump?

Gently. Heat pumps run best with steady, low flow temperatures, so use the thermostat for comfort and small setbacks rather than big on-off swings.

BEAMA's heat pump controls guide says heat pump systems should have weather compensation or internal temperature control, plus a timer, and that wet systems should keep a minimum flow of water to avoid short cycling. One heat pump maker says combining weather compensation with setback is counterproductive. If you do use both, it advises limiting the setback to 2°C including hysteresis, keeping setback periods short, and reducing or removing setback in long cold spells.

In practice, set each room thermostat to a steady comfort temperature with a small night setback, and let the heat pump's own weather compensation set the flow temperature.

What are the common smart thermostat mistakes on UFH?

• One smart thermostat for the whole house. It cannot open the actuators room by room.
• Buying a thermostat that does not match the wiring centre. A battery thermostat will not work on a wired UH8, and a 230V thermostat will not work on a UH8-RF.
• No floor probe under wood or vinyl. The floor limit cannot work without one.
• Using a 3A water UFH thermostat on an electric mat. Electric floors need a 16A thermostat such as the neoStat-e.
• Big daily on-off cycles on a screed floor. The floor never catches up. Use optimum start and a modest setback.
• Paying for WiFi thermostats in every room of a large house. A hub is cheaper from about five rooms.

Frequently asked questions

Can I use a single smart thermostat for underfloor heating?

Only if the whole floor is one zone, such as a single extension. For a house with several rooms, BEAMA says each room needs its own thermostat or sensor, and Part L asks for room-by-room temperature control in most cases.

Do I need a hub for Heatmiser smart thermostats?

The neoStat V3 and neoAir need a neoHub for app control. The neoStat WiFi connects directly to your router on 2.4GHz WiFi and does not need one.

Do Heatmiser thermostats work with Alexa and Google Home?

Yes, through the neoHub. Heatmiser lists Alexa, Google Home, Apple Home and IFTTT integration.

How many thermostats can one neoHub control?

Heatmiser says the neoHub links up to 32 neo devices, including neoStat, neoAir, neoStat-e and neoPlug.

What is optimum start on a UFH thermostat?

It starts the heating early so the room reaches its set temperature at the programmed time, rather than starting to warm up at that time. On the neoStat V3 it can be set up to 5 hours, and it works from a rate-of-change setting in minutes per degree.

Will a smart thermostat cut my bills?

It may, if you use its schedules, setback and holiday mode. A government review found no consistent evidence of a set saving from heating controls, so the saving depends on how you use it.

What floor limit should a smart thermostat have for vinyl or wood?

Use the flooring maker's maximum. BEAMA gives 27°C as an example for some vinyl floors. Heatmiser's neoStat V3 defaults to 28°C and can be set from 20 to 45°C.

Sources: BEAMA Part L 2022 heating controls guidance, BEAMA underfloor heating controls guide, BEAMA heat pump and electric heating controls guide, DECC: how heating controls affect domestic energy demand, Which? (Energy Saving Trust comment), Heatmiser neoStat V3 datasheet, Heatmiser neoHub, Heatmiser FAQ: neoAir batteries