Thermostatic radiator valve: how to choose and set it
In short
- A thermostatic radiator valve has a body, fitted on the radiator's flow pipe, and a head that sets the room temperature. The body is chosen by connection type: angled, straight or reverse angled.
- On most heads, setting 3 is about 19 to 20 °C and each step is 2 to 3 °C (source: Energuide). Each manufacturer has its own scale: on our Belrad M30 head, setting 3 is 20 °C according to its technical sheet. Lowering the temperature by one degree cuts consumption by about 7% (source: écoconso).
- In the room with the main thermostat, valves stay fully open on 5. Our models range from €5.67 for a head to €53.18 for a designer valve.
A thermostatic radiator valve automatically controls each radiator according to the room temperature. When the air reaches the chosen value, it reduces the hot water flow, then opens again as the room cools. This guide explains how to choose and set the right model, with the real references and prices from our range.
Last updated: October 2026. Prices and availability recorded in the shop on 20/10/2026, VAT included.
Body and head: what is a thermostatic valve made of?
A thermostatic valve has two parts. The body is screwed onto the radiator's flow connection and holds the valve pin. The numbered head holds the temperature-sensitive element that presses or releases that pin.
Both parts are sold separately or together. If the body is in good condition, you can replace only the head.
Angled, straight or designer: which body?
The body is chosen according to the shape of the connection between pipe and radiator, not the radiator itself.
| Model | For which connection | Price incl. VAT |
|---|---|---|
| Angled thermostatic valve 1/2" | The most common, connection at an angle | €6.58 |
| Straight thermostatic valve 1/2" | Connection in line with the pipe | €7.10 |
| Reverse angled thermostatic valve 1/2" | Head facing the other way | €7.10 |
| Belrad M30 white thermostatic head | Screws onto the valve body | €5.67 |
| Designer wall and floor thermostatic valve (chrome) | Matching body and head, 16 mm connection | €35.53 |
| Designer wall and floor thermostatic valve (brushed copper, brushed gold, grey bronze) | Finishes matching designer radiators | €53.18 |
Standard bodies and heads are in our connection parts collection. Designer thermostatic valves are available for vertical and designer radiators, with floor or wall connection.
The M30 thread: what fits what?
The head screws onto the body. Our Belrad head uses an M30 thread, stated in its name. Before buying a head on its own, check that your valve body takes the same thread: otherwise the head will not fit without an adapter.
How do you set a thermostatic valve?
Most heads are numbered 1 to 5 with a frost setting marked by an asterisk. The numbers are comfort levels, not exact temperatures, because the result depends on the room (outside walls, windows, other heat sources). These are the general values given by Energuide, and those of our Belrad M30 head according to its technical sheet:
| Setting | General guide (Energuide) | Our Belrad M30 head (technical sheet) |
|---|---|---|
| * | about 6 °C (frost protection) | 6 °C |
| 1 | about 15 °C | 12 °C |
| 2 | about 17 °C | 16 °C |
| 3 | about 19 to 20 °C | 20 °C |
| 4 | about 22 °C | 24 °C |
| 5 | fully open | 28 °C |
Scales vary from one manufacturer to another: on our Belrad M30 head, each step is about 4 °C and the setting range runs from 6 to 28 °C. For another head, follow its manual or technical sheet.
Écoconso gives examples by room: 20 °C (setting 3) for a bedroom used during the day, 16 to 17 °C (setting 2) for the kitchen, 23 to 24 °C (setting 4) for a bathroom in use and 12 to 14 °C (setting 1) for an unused bedroom.
Turning the head to 5 does not heat the room faster: it only raises the target temperature. According to écoconso, each degree lower cuts consumption by about 7%.
Where should valves not be turned down?
In the room with the main room thermostat, leave the valves fully open on 5. The thermostat already limits the heating: a closed valve in that room stops the thermostat reaching its setpoint, and the boiler runs longer (source: écoconso).
Do not hide the head behind a curtain, furniture or a radiator cover either: it would measure the warm air around it and shut too early.
In summer, set all valves to 5 so the mechanism does not seize (source: écoconso).
Thermostatic valve or room thermostat?
They work together. The room thermostat controls the boiler from one reference room. Thermostatic valves control every other room separately. Our range includes five room thermostats. As of 20/10/2026, only the RQ 10 and the Belux TI-N are available, the other three are out of stock:
| Model | Price incl. VAT | Availability |
|---|---|---|
| RQ 10 thermostat | €8.07 | Available |
| Belux TI-N room thermostat | €18.59 | Available |
| Belux Light BT-D LCD, non-programmable | €41.77 | Out of stock |
| 950C electronic thermostat | €60.63 | Out of stock |
| Belux Light BT-D LCD, programmable | €70.45 | Out of stock |
What about the return side of the radiator?
On the radiator outlet goes a lockshield (balancing) valve or return valve, used to balance flow between radiators. Our 1/2" angled return valves cost €4.37. Our 1/2" balancing tees are currently out of stock.
Frequently asked questions about thermostatic radiator valves
What is the difference between a thermostatic valve and a manual valve?
A manual valve opens or closes the radiator regardless of temperature. A thermostatic valve reduces the hot water by itself once the room reaches the chosen temperature.
Which number should a thermostatic valve be set to?
Setting 3 gives about 19 to 20 °C according to Energuide, and 20 °C on our Belrad M30 head according to its technical sheet. Scales vary by manufacturer: check your head's manual. Écoconso cites setting 2 for the kitchen, setting 1 for an unused bedroom and setting 5 in the room with the room thermostat.
Can I replace just the thermostatic head?
Yes, if the valve body is in good condition and the thread matches. Our white Belrad M30 head costs €5.67.
Do you need a thermostatic valve in the room with the thermostat?
It can stay, but set to 5. Otherwise it stops the room thermostat reaching its setpoint (source: écoconso).
How much does a thermostatic valve save?
It stops little-used rooms from overheating. As an order of magnitude, écoconso states that one degree lower cuts consumption by about 7%.
See thermostatic valves and heads
Bodies, heads and designer valves are online with their specifications: see thermostatic valves and heads or see designer valves. Collection is available at our shop in Schaerbeek.
Sources: Energuide, on thermostatic valve settings · écoconso, on setting thermostats and radiators · Belrad, technical sheet of the M30 thermostatic head (BLR213).