Basics of Hydronic Floor Heating

1. What is a hydronic floor heating system?

Answer: The full name of a hydronic floor heating system is “low-temperature hot water radiant floor heating.” It uses hot water at a temperature not exceeding 60°C as the heat transfer medium. The water circulates through heating pipes embedded in the floor screed to heat the floor, which then radiates heat into the room.

2. What are the components of a hydronic floor heating system?

Answer: The floor surface layer, thermal insulation layer, structural layer, underfloor heating pipes, heat source or hot water supply pipes, manifold, control valves, thermostats, and electric actuators, etc.

3. Are there national standards for underfloor heating?

Answer: Yes, the Technical Specifications for Radiant Floor Heating (JGJ142-2004) issued by the Ministry of Construction of the People’s Republic of China in 2004.

Common Misconceptions About Underfloor Heating

4. Is it better for underfloor heating to be as hot as possible?

Answer: Many people still hold the misconception that the hotter the underfloor heating, the better—to the point where they wear only underwear indoors and keep windows open. In reality, this is neither comfortable nor energy-efficient, as opening windows allows most of the heat to escape. Excessively high temperatures create a large indoor-outdoor temperature difference, increasing the risk of catching a cold. In fact, the goal is for underfloor heating to be as comfortable as possible. The system should be equipped with a control system to regulate temperature, just like an air conditioner.

5. Can underfloor heating pipes leak?

Answer: Each run of underfloor heating pipe is laid as a single, continuous length with no joints in the middle. As long as they are not damaged by human error, they will not leak.

6. Which has a longer service life: underfloor heating or radiators?

Answer: Currently, the national standard for the service life of new radiators is 15 years, while the standard for underfloor heating is 50 years.

7. Is it necessary to clean underfloor heating pipes?

A: Water accumulates inside underfloor heating pipes year-round. This water contains microorganisms and impurities, which can form biological slime under certain conditions. This slime adheres to the inner walls of the pipes, increasing thermal resistance and reducing heat transfer. Regular pipe cleaning will make the underfloor heating system more energy-efficient and comfortable.

8. Can I convert to underfloor heating in a building with centralized heating?

A: Centralized heating and underfloor heating are different systems. You must obtain approval from the property management and your neighbors, as underfloor heating creates higher resistance that can disrupt system circulation, potentially causing neighboring units to remain cold (individual unit heating is preferable). However, many northern cities are now converting radiators to underfloor heating. In communities with centralized heating, the hot water temperature is typically 60–90°C. If this water is directly connected to an underfloor heating system, the temperature is clearly too high. This not only causes discomfort due to excessive surface heat but also shortens the lifespan of the underfloor heating system. We recommend installing a floor heating mixing and cooling unit to regulate the water temperature within the system to the required range of 35–50°C. By installing a thermostat indoors, you can safely use the floor heating system.

9. Can the underfloor heating system be controlled like an air conditioner?

Answer: Yes, it supports room-by-room temperature control, adjustment, and on/off operation. By installing an underfloor heating thermostat, you can set water temperature, room temperature, and schedule operations. You can even program weekly schedules for automated control. This provides both smart, comfortable heating and effective energy savings to reduce costs.

10. Does underfloor heating lose heat downward?

Answer: The insulation layer of the underfloor heating system ensures that heat is primarily radiated upward. Any heat that might be transferred downward is mainly through conduction. The floor must first be covered with an insulation layer, typically 2–3 centimeters thick. Even if there is any heat conducted downward from the underfloor heating system, it is minimal and can be considered negligible.