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Understanding the Hydronic Heating System

Discover how a hydronic heating system works, the components that make it up, the types, and the benefits of this system

As we all know, a hydronic heating system uses water as a thermal fluid to efficiently and flexibly distribute thermal energy, using a single circuit to heat and cool the environment.

In this article, we will explore some fundamental aspects to deepen the knowledge of this type of system, also showing you how to operate with a BIM software for MEP systems.

Hydronic heating system diagram

Hydronic heating system diagram

What is a hydronic heating system?

Before delving into the different topics, it is good to make a small introduction to what a hydronic heating system is.

A hydronic heating system is a system that distributes thermal or cooling energy using water as a thermal fluid.

The heart of the system is the heat generator, often a heat pump like an air-water heat pump, but it can also be integrated with a gas boiler. Water, thanks to its high heat capacity, carries heat through the distribution network, which is composed of well-insulated pipes and circulation pumps.

At the terminals, such as fan coil units, the water heats or cools the environment through thermostatic devices. This system, also known as a hydronic system or hydronic air conditioner, is particularly efficient due to the water’s ability to transport heat effectively.

Main components of a hydronic heating system

In a hydronic heating system, there are several components used for the correct operation of the entire system. Below is a list of the main parts:

  1. generator – this component is responsible for producing heat or cold within the system. The most common generators are heat pumps and gas boilers, although the latter can only provide heat. The heat pump, especially the air-water type, is often used for its ability to efficiently produce heat even at low temperatures;
  2. pipes – pipes are used to transport hot or cold water from the generator to the distribution terminals inside the building. They must be well insulated to prevent heat loss and condensation along the distribution path;
  3. distribution terminals – these devices receive hot or cold water from the pipes and transfer heat to the surrounding environment. They can include radiators, fan coil units, or underfloor cooling systems. Distribution terminals play a crucial role in ensuring thermal comfort inside the building;
  4. circulation pumps – circulation pumps are used to push water through the pipes and ensure uniform heat distribution throughout the building. They are essential for the proper operation of the hydronic system and to maintain a constant temperature in all areas of the building;
  5. control devices – these components regulate the water flow and temperature within the system to maintain the desired thermal comfort. They can include thermostats, thermostatic valves, and automation systems that allow you to program and control the system according to specific needs;
  6. insulating materials – are used to thermally insulate the pipes and reduce heat losses along the water distribution path. Proper insulation is essential to maximize the energy efficiency of the hydronic system and reduce energy consumption;
  7. safety devices – can be included in the system to protect against pressure surges, water leaks, or other emergency situations that may occur, ensuring the safety and reliability of the system;
  8. heat exchangers – these components allow heat exchange between the hot water from the heat generator and the surrounding environment through the distribution terminals. They can be present in both radiators and fan coil units to transfer heat to the indoor air;
  9. storage tanks – can be used to store hot water for sanitary use or to ensure a heat reserve for the heating system. These tanks can be connected to the heat generator and allow for a continuous supply of hot water;
  10. filters and purification devices – can be integrated into the distribution terminals to purify the air entering the environment. These filters help remove dust particles, allergens, and other contaminants present in the air, thus improving indoor air quality;
  11. humidity control system – some hydronic systems may also include devices for controlling air humidity, which allow maintaining optimal humidity levels inside the building. These systems are particularly useful in environments where specific relative humidity levels need to be maintained to ensure occupants’ comfort and prevent mold and condensation formation;
  12. monitoring and remote management devices – with advancing technology, more and more hydronic systems are equipped with monitoring and remote management devices that allow controlling and regulating the system remotely through smartphones, tablets, or computers. These devices offer greater flexibility and control to users, allowing them to optimize the energy efficiency of the system and save on energy costs.

3D model of a hydronic radiant system

3D model of a hydronic radiant system

Types of hydronic heating systems: hydronic radiant systems

Hydronic radiant systems typical of residential and tertiary sectors consist of plastic material coils immersed in building structures, generally isolated from adjacent rooms. These systems use water at different temperatures depending on the need to heat or cool the spaces.

They can be installed in the floor, wall, or ceiling and are suitable for both new constructions and renovations of existing buildings. In the case of radiant floors, the pipes can be embedded in the screed, positioning the tubes above the insulating layer, which can be flat or relief.

The main components of a hydronic radiant system include:

  1. generator: usually a boiler (only for the winter period) or a heat pump, which treat the water before sending it through the radiant system;
  2. pipes: usually made of cross-linked polyethylene (PEX), which transport water from the generators to the radiant elements;
  3. radiant elements: can be floor, wall, or ceiling systems, consisting of pipes or special panels that distribute heat evenly in the environment;
  4. valves and circulation pumps: regulate the flow of hot water through the system and ensure uniform heat distribution.

The system stratigraphy includes several elements, from top to bottom:

  • a surface covering (such as parquet, tiles, PVC, etc.);
  • a support layer (screed) with pipes made of plastic material;
  • a protective layer for insulation;
  • an insulating layer that must comply with standards.

Hydronic radiant systems offer several advantages, including uniform thermal comfort, efficient heat distribution, better air quality, and higher energy efficiency compared to traditional heating systems. They are particularly suitable for large spaces and can be integrated with cooling systems to provide year-round comfort.

Plan representation of a hydronic radiant system

Plan representation of a hydronic radiant system

Advantages and disadvantages of hydronic heating systems

Like any HVAC system, hydronic heating systems have advantages and disadvantages. Let’s compare hydronic systems with other heating and cooling solutions, highlighting their advantages in terms of energy efficiency, thermal comfort, and cost savings. Let’s see them in detail.


  • single solution for air conditioning: the versatility of hydronic systems allows managing both heating and cooling using a single infrastructure, offering an integrated solution throughout the year;
  • reduced consumption: thanks to its operation at low temperatures, hydronic systems guarantee significant energy cost savings, contributing to reducing bills;
  • safety: the use of water as a thermal fluid makes hydronic systems safe and flexible, suitable even for special environments such as food production spaces, operating rooms, and industrial plants, as any leaks do not pose risks of environmental pollution;
  • flexibility: the ability to integrate hydronic systems with other solutions, such as radiant panels or induction heating, offers broad design flexibility. This integration allows maximizing energy efficiency, leveraging natural cooling that exploits temperature differences with the surrounding environment;
  • sustainability: hydronic systems are environmentally friendly and sustainable, reducing CO2 emissions and offering a low environmental impact solution;
  • maximum convenience: implementing a hydronic system is one of the most widespread and consolidated air conditioning options. Thanks to this diffusion, it is possible to intervene easily in the design, installation, and maintenance phases, making the whole process very convenient and accessible.


  • initial costs: installing a hydronic system may involve higher initial costs compared to other traditional solutions, due to the need for larger pipes, condensate drains, and additional electrical wiring;
  • startup times: hydronic systems may take longer to reach the desired temperature compared to other faster systems, such as direct expansion or boiler systems.

Video on how to design a hydronic heating system

Below you can see how to design a hydronic heating system with a BIM software for MEP systems.