A Dutch installer sends an inquiry for two thousand thermal actuators. His first question is not about the price. He asks whether the unit is normally closed, what the adapter thread is, and how long it takes to close after the thermostat drops the signal. This kind of inquiry is very common in the Netherlands. Dutch buyers ask technical questions from the beginning, and they expect a technical answer. To understand why they work in this way, it helps to look at what has happened to heating in the Netherlands over the past ten years.
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The Gas Transition That Changed Dutch Heating
For a long time the Netherlands was one of the most gas dependent countries in Europe. The Groningen field made natural gas cheap and easy to obtain, and almost every home was built with a gas boiler and radiators. That situation has now changed, and the change was driven by policy rather than by consumer preference.
Since 1 July 2018, new residential buildings in the Netherlands no longer receive an automatic connection to the gas network. Developers must plan a different heat source from the design stage. In practice this usually means an air to water heat pump, sometimes a district heating connection, and in some projects a ground source system.
Then in 2021 the BENG requirements came into force for all new buildings. BENG stands for Bijna Energieneutrale Gebouwen, which means nearly energy neutral buildings. It sets three separate limits: the energy demand of the building, the primary fossil energy use, and the minimum share of renewable energy. A building that fails any one of the three indicators will not receive a permit. The Netherlands Enterprise Agency, RVO, publishes the current calculation rules.
The consequence for equipment is straightforward. A heat pump cannot produce 70°C water efficiently, and traditional radiators need high temperature water to deliver enough output. So the emitter had to change. Underfloor heating became the standard solution instead of a premium upgrade. In Dutch this is called vloerverwarming, and today it appears in nearly every new residential project.
Why Low Flow Temperature Works So Well in This Climate
The Dutch climate is well suited to this approach, and the temperature numbers explain the reason clearly.
Winter in the Netherlands is cold but not severe. Daytime highs from December to February are usually around 5°C to 7°C, and night temperatures sit close to 0°C. Only in colder years does the temperature drop below -5°C, and this normally happens in January or February. Coastal areas stay milder than inland regions because of the North Sea. Long term records from the Royal Netherlands Meteorological Institute show this pattern is stable.
For a heat pump, outdoor temperature is what determines efficiency. When the outdoor air stays above -5°C for most of the season, an air to water unit can hold a COP above 3.5 through the majority of the heating hours. In a continental climate with a design temperature of -15°C, the same unit would spend far more hours in a low efficiency range, or it would need an electric backup heater to cover the peak.
This is the technical reason why Dutch projects are designed around a flow temperature of 35°C. Combine that low temperature with a very large emitting surface, which is what a floor provides, and the system delivers the required output without asking the heat pump to work outside its efficient range. Refrigerant choice matters here as well, and units using R32 refrigerant perform well at the modest lift these systems require.
| Emitter Type | Typical Flow Temperature | Suitable for Heat Pump | Practical Note |
|---|---|---|---|
| Cast iron radiator, older stock | 70 to 80°C | No | Needs a boiler or a high temperature heat pump |
| Standard panel radiator | 55 to 70°C | Poor | COP falls sharply at this lift |
| Oversized low temperature radiator | 45 to 50°C | Acceptable | Common retrofit compromise when floor height is limited |
| Underfloor heating | 30 to 40°C | Yes | Best match, large surface area, even distribution |
| Underfloor heating with cooling | 30 to 40°C heating, 16 to 18°C cooling | Yes | Same circuit is reused in summer, requires dew point control |
What Dutch Projects Actually Specify
Selling into the Netherlands is different from some other markets, because the specification usually arrives before the price negotiation. The reference document most installers follow is ISSO 49, the Dutch guideline for floor heating and floor cooling in dwellings, while heat loss is calculated according to ISSO 51 for small buildings. When an installer quotes ISSO in an email, he is telling you that the project has already been engineered and that any substitution will need to be justified.
The requirements below are the ones that appear most often in the Dutch inquiries we receive.
| Component | What Dutch Projects Usually Ask For | Reason |
|---|---|---|
| Floor heating pipe | PE-RT or PEX, 16 x 2.0 mm or 20 x 2.0 mm, oxygen barrier to DIN 4726 | Oxygen diffusion corrodes the steel and brass parts of the circuit |
| Manifold | Stainless steel or brass, 1 inch main, 2 to 12 ports, per-loop balancing with flow meters | Dutch installers balance every loop individually, so branch flow capacity must be known |
| Thermal actuator | 24V normally closed, M30 x 1.5 adapter, EN 60730 | M30 x 1.5 is the dominant valve head thread on Dutch manifolds |
| Room thermostat | Modulating control, OpenTherm or 0 to 10V, individual room zoning | On/off switching limits how well the heat pump can modulate |
| Wiring centre or base station | Multi zone, pump and boiler contact, 24V output, EN 60730-2 | Standard control architecture in Dutch multi room systems |
| Screed | Anhydrite is common, minimum 30 mm cover above the pipe | Better conductivity and a thinner total build up than sand cement |
One item is worth extra attention. The OpenTherm protocol was developed in the Netherlands and it is still widely expected there. A thermostat that only supports on/off switching will restrict heat pump modulation, and a Dutch installer will notice this during commissioning. Modulating models such as the Apus RT-A1 are designed with this requirement in mind.
Legom Component Data Against These Requirements
The points above are market requirements. Below are the measured values from our own production, so a Dutch designer can check them against a system calculation without waiting for a datasheet.
| Parameter | Legom Value | Standard | Relevance to a Dutch System |
|---|---|---|---|
| Oxygen permeability, PE-RT 5-layer | ≤ 0.32 mg/m²d at 40°C | DIN 4726 | Protects manifold valves, pump and heat exchanger over the system life |
| Thermal conductivity at 60°C | 0.41 to 0.43 W/m°K | DIN 52612 | Input for output calculation at a 35°C flow temperature |
| Thermal expansion, PE-RT 5-layer | 0.15 x 10-4 m/m°K | DIN 53752 | Dimensional stability in the long loops used in narrow terraced houses |
| Roughness coefficient, PE-RTII | 0.0015 mm | Prandtl-Colebrook | Direct input for pressure drop and circulation pump sizing |
| PEX cross-linking degree | above 65 percent | DIN 16892 | Creep strength for loops under sustained stress |
| Actuator power consumption | 2 W per unit | EN 60730 | Auxiliary electrical load, see the note below |
| Actuator closing and opening time | 3 to 5 min closing, 60 to 90 sec opening | EN 60730 | Determines control response and commissioning behaviour |
| Actuator force and stroke | 100 ± 10 N, stroke ≥ 4 mm, IP54 | EN 60730 | Must exceed the closing force of the manifold valve head |
| Manifold flow capacity | 12 Kv brass, 20 Kv stainless, 1.5 Kv per branch | m³/h | Sets the maximum zone count the manifold can serve |
| Manifold rating | 16 bar, 110°C, 50 mm branch spacing | Water medium | Far above the 35°C and 3 bar of a normal Dutch floor circuit |
One figure is worth working through, because it is often left out of Dutch energy calculations. A thermal actuator draws 2 W while it holds a valve open. A ten zone house with one actuator per loop therefore adds up to 20 W of continuous auxiliary load whenever every zone calls for heat. Over a heating season this is small next to the compressor, but it is not zero, and under BENG the auxiliary load belongs in the primary energy figure. Designers who zone aggressively, with twelve or more small loops, should count it. The base station architecture matters here as well, since it determines how many actuators can be energised at the same time.
Where a project needs something outside the standard range, such as a manifold supplied with integrated flow meters, a different branch count, or a specific connection thread, this is handled through our OEM and ODM service. Send the requirement and the engineering team will confirm what is possible before you commit to a sample.
What It Is Like to Supply Dutch Customers
The technical detail described above is not a formality. It shapes how the whole commercial relationship works, and suppliers used to price led markets often need some time to adjust.
“When we started supplying to the Netherlands, I noticed something different straight away. Dutch customers already know what they want before they contact us. They send the details first and the price question comes later. In the beginning our team found this demanding. Now we prefer it, because when a customer is clear from the start we make fewer mistakes, and everything after the first order goes much more smoothly.”
— Maggie Shen, Director of Legom
Cooling Is Now Part of the Same Discussion
Something that surprises suppliers new to this market is how often cooling appears inside a heating inquiry.
Under BENG, Dutch new build projects must also satisfy TOjuli, an indicator that measures the risk of summer overheating. Modern Dutch homes are very well insulated and airtight, which is excellent in winter but can produce uncomfortable indoor temperatures in July and August. Passive measures such as external shading are applied first, but many projects also use the floor circuit for cooling.
The same floor heating pipes carry water at around 16°C to 18°C in summer. The floor absorbs heat from the room instead of releasing it. Output is modest, usually 15 to 25 W/m², so it will not behave like an air conditioner. What it does is remove the peak, and it does this using equipment that is already installed in the floor.
There is one condition that cannot be ignored. If the floor surface falls below the dew point, condensation will form on it. A Dutch cooling system therefore needs a dew point sensor, or at minimum a humidity sensor connected to the control, and the supply temperature must be limited automatically. A room thermostat that cannot handle a heating and cooling changeover signal is not suitable for these projects.
Retrofit Is Where the Volume Is
New construction receives most of the attention, but the existing housing stock is where the larger opportunity sits. The Netherlands has roughly eight million homes, and the large majority of them were built for gas heating with radiators.
Retrofitting underfloor heating into these houses is not simple. Available floor height is often limited, particularly in the narrow terraced houses that are common in Dutch city centres. This has created strong demand for low build up systems, where the pipe sits inside a thin panel with a total height of 12 to 20 mm instead of a 60 mm screed. Milling systems, where grooves are cut into an existing screed and the pipe is laid inside them, are also used.
For a supplier, this means the Dutch market does not want a single configuration. It wants a range of pipe diameters, thinner pipe for retrofit panels, and compact manifolds that fit inside small utility cupboards. A manufacturer who can only offer the standard new build configuration will lose a significant part of the available business.
Frequently Asked Questions
Does underfloor heating work well with a heat pump in the Dutch climate?
Yes, and this combination is now the default in Dutch new build housing. The reason is the mild winter. Because outdoor temperatures rarely fall below -5°C, an air to water heat pump can maintain a seasonal COP above 3.5 in most Dutch installations. Underfloor heating allows a flow temperature of around 35°C, which sits inside the efficient operating range of the unit. With radiators the required flow temperature would be 55°C or higher, and efficiency would drop considerably. The pairing works so well that Dutch energy performance calculations under BENG effectively assume it for most residential designs.
Can an older Dutch house be retrofitted with underfloor heating?
Yes, but the method depends on how much floor height is available. If there is room for a full screed, the standard approach can be used. In many Dutch homes, particularly older terraced properties, that height does not exist. In those cases installers use low build up systems with a total height of 12 to 20 mm, or milling systems that cut grooves into the existing screed. Before any of this, the heat loss of the house should be recalculated. A 35°C flow temperature cannot cover the heat loss of a poorly insulated building, so insulation work normally comes first. Many Dutch retrofits are carried out in two stages: insulation and glazing first, then the heating system.
What approvals do components need for the Dutch market?
For the Netherlands and the wider European market, components need CE marking under the relevant directives. Pipe with an oxygen barrier is expected to comply with DIN 4726, and Legom pipe is held to ≤0.32 mg/m²d at 40°C against that standard. For electrical items such as actuators, thermostats and wiring centres, EN 60730 applies for automatic electrical controls, together with RoHS compliance. Beyond the legal minimum, most Dutch wholesalers will ask for test reports and a declaration of conformity before opening an account, and many will request KOMO or Kiwa certification for pipe systems. It is worth preparing this documentation before approaching Dutch distributors, because they usually ask for it at the first stage of the conversation.
Checked and updated by Maggie Shen, Director at Legom, on 22 July 2026. The component figures in this guide are taken from Legom production specifications, and the market context reflects our supply work with installers and wholesalers in the Netherlands.