District heating and thermostat: How do they work together?
More and more buildings are connected to district heating systems. Instead of an individual gas boiler, heat is supplied through underground pipes from a central network. But how do you regulate temperature without a boiler? And what role does the thermostat play in such a system?
The thermostat remains the heart of temperature control—it decides when heat is needed and how efficiently it’s delivered. With proper thermostat settings—and, more importantly, with smart data monitoring—you can significantly reduce both consumption and costs.
How does a thermostat work with District heating?
With district heating, heat is not generated inside the building, but supplied via a centralized heating network. Each building receives hot water through a heat interface unit (HIU)—a compact system that transfers heat from the network to the internal heating circuit.
How It Works
1. Heat supply
Hot water—typically between 70°C and 90°C—flows from the district heating network to the HIU inside the building. This water comes directly from a central heat source and does not mix with the internal system.
2. Heat sources outside the building
The heat is produced centrally and can come from various renewable or residual sources, such as:
- Industrial or data center waste heat
- Combined Heat and Power (CHP)
- Waste incineration plants
- Geothermal energy
- Large-scale heat pumps
These sources feed the network, distributing heat through insulated pipes to connected buildings.
3. The role of the heat interface unit (HIU)
The HIU is installed inside the building—often in a utility or technical room—but it is not a heat source.
Instead, it contains a heat exchanger that transfers heat from the network water to the internal heating circuit.
In larger properties, multiple HIUs or sub-units can be used per floor or zone for better control.
The network water and building water remain completely separate, improving safety and system reliability.
4. The role of the thermostat
The thermostat (or building control system) sends a signal to a control valve within the HIU.
- When the indoor temperature drops below the setpoint, the valve opens, allowing more hot water to flow through the heat exchanger.
- Once the target temperature is reached, the valve closes automatically.
This maintains a stable indoor temperature—without any need for a boiler.
5. Radiators, underfloor heating, and zone control
The heated water from the HIU circulates through radiators, underfloor systems, or air-handling units.
In larger buildings, each zone can be controlled separately for optimal comfort and energy efficiency.
6. Smart thermostats and Building Management Systems (BMS)
Modern systems go far beyond a simple wall thermostat.
With smart thermostats or an Energy Management System (EMS), building managers can monitor, analyze, and adjust heating performance in real time—based on occupancy, weather, or energy tariffs.
For low-temperature systems such as underfloor heating, it’s best to maintain a steady temperature rather than frequent adjustments, which can reduce efficiency.
7. Key difference from conventional central heating
In a traditional boiler system, the heat source (the boiler) is located inside the building. With district heating, however, the heat comes from outside the building, and the heat interface unit (HIU) only transfers that heat to the internal circuit.
The thermostat or building control system therefore does not control a boiler, but instead regulates a valve that manages the flow of hot water through the HIU.
Because of this, the system usually responds slightly slower to temperature changes, making it essential that the thermostats, HIU, and heating distribution system are well-coordinated to maintain both comfort and efficiency.
Which thermostats are suitable for district heating?
Not all thermostats are compatible with district heating. The main types are:
1. On/Off Thermostat
A simple control that opens or closes the valve. Effective for standard setups but less efficient with variable heating demand.
2. Modulating Thermostat
Adjusts heat output gradually for more stable temperatures. Some use protocols like OpenTherm, enabling smarter communication with the HIU.
3. Smart Thermostat
The latest generation learns from user behavior, adjusts based on outdoor temperature, and can be controlled remotely via an app.
Smart thermostats: Comfort and cost savings
A smart thermostat does more than regulate temperature. When combined with an Energy Management System (EMS), it collects and analyzes data such as:
- Heat consumption per room or building zone
- Supply and return temperatures
- Inefficient heating patterns or unnecessary demand
- Comfort levels versus energy performance
These insights open up new opportunities for optimization:
- Automatically lower heating when rooms are unoccupied
- Reduce peak load in the heating network
- Detect malfunctions earlier
For property owners, housing associations, and municipalities, this data provides a clear view of usage and performance—essential for reducing costs and carbon emissions.
Read more: Energy Management System for Businesses
Practical tips for residents using district heating
To get the most from district heating, users should understand how the thermostat interacts with the system.
Tips for efficient operation:
- Keep temperatures constant: District heating works more efficiently with stable indoor temperatures than frequent on/off adjustments.
- Night setback: Lower the temperature only slightly (1–2°C) at night to avoid excessive reheating.
- Keep radiators open: Especially in living or high-use areas, open radiators ensure even heat distribution.
- Monitor return temperature: A high return temperature means too little heat is extracted—indicating inefficiency that affects the entire network’s performance.
Thermostat settings for property managers: Data as a performance driver
In commercial and multi-tenant buildings, smart temperature management plays a crucial role.
Through data-driven monitoring, facility managers can:
- Adjust heating based on occupancy levels
- Benchmark building performance
- Detect faults or waste early
- Automate ESG and CSRD reporting
In collective systems, thermostat data can even be linked to billing data, ensuring fair cost allocation between tenants.
Also read: Billing Data – Fair and Efficient Energy Costs for Businesses
Conclusion: The future of district heating starts with smart thermostats
The combination of district heating, smart thermostats, and real-time data is transforming the way we manage energy.
In the near future, heating systems will automatically optimize performance based on:
- Energy prices
- Weather forecasts
- Occupancy data
- CO₂ targets
This means district heating will not only be comfortable, but also predictive, efficient, and sustainable.
Frequently Asked Questions (FAQ)
Does a thermostat work differently with district heating than with a boiler?
Yes. The thermostat doesn’t control a boiler but manages heat flow via the HIU valve.
Can any thermostat be used with district heating?
No. Only thermostats compatible with district heating or OpenTherm communication protocols.
Is a smart thermostat worth it with district heating?
Yes—especially when combined with an EMS for greater insight, comfort, and efficiency.
How can I tell if my district heating system is efficient?
Monitor your return temperatures and consumption data. High return values indicate heat loss.
What are the benefits for property managers?
Real-time insight, fewer faults, automated reporting, and lower energy costs.