Improving Comfort and Air Quality with Underfloor Heating

Michael Tobias
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    Underfloor heating provides a viable alternative for conventional heating systems. Instead of using forced airflow from above, heat is released at floor level. Ceiling-based heating systems must work against natural convection, while underfloor systems use it to their advantage. This is beneficial in terms of energy efficiency, occupant comfort, and indoor air quality.

    There are two main types of underfloor heating systems. Radiant floors use embedded resistance heaters or hot water pipes, which means that the floor itself releases heat. On the other hand, trench heaters are installed along floor openings and covered with ventilation grilles.

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    Architects and interior designers can also use underfloor heating to hide components that clash with their design intent. In the case of trench heating, the ventilation grilles can be specified with a material and color that match the interior design.

    How Does Underfloor Heating Save Energy?


    When heat is delivered from below, warm air is distributed by natural convection at zero energy cost. On the other hand, air must be forced downward with fans when heat is delivered from above. There are two factors that increase energy consumption in the second case:

    • The fan power necessary to establish an airflow that overcomes natural convection.
    • Additional heating is also required, to compensate for the inefficient air distribution.

    In the case of radiant floors, hydronic piping systems have a lower operating cost than electric resistance systems. Heating water with a boiler or heat pump is less expensive, compared with heating the floor directly with resistors. Electric radiant floors are easier to install, but their operating costs over time are much higher.

    Since trench heaters are in direct contact with indoor air, they can be equipped with fans for faster heating. However, fans are an optional feature and the system can operate with only natural convection. On the other hand, ceiling-based heating systems need a continuous forced airflow to move warm air downward. Fan-assisted trench heaters can use electronically commutated motors or ECMs, which offer up to 75% savings compared with single-speed fan motors.

    How Does Underfloor Heating Improve Comfort?


    Since forced air systems must overcome natural convection, they require a high ventilation rate. However, this produces air turbulence and drafts, which may cause discomfort for occupants. The uneven heat distribution also creates cold spots at floor level, adding to the discomfort.

    Underfloor heating eliminates both the air drafts and the cold spots at floor level, making indoor spaces more comfortable during the winter months. In business settings, a comfortable environment also boosts productivity. Underfloor heating systems are also silent, since no fans are required for heat distribution.

    Radiant heating in particular also offers a safety benefit when used outdoors. Since heat is released from the floor, ice and water are not allowed to accumulate. This keeps the floor from getting slippery, preventing falls and other accidents.

    How Does Underfloor Heating Improve Air Quality?

    In conventional heating systems, the drafts caused by forced airflow also have a negative impact on air quality. The turbulent air movement can spread dust and other particles, and even pathogens like coronavirus. When someone with an infectious disease enters a drafty area, others are more likely to get infected. Underfloor heating helps mitigate this risk by reducing air circulation.


    Underfloor heating also reduces air movement between different building areas, since heat is released from floors and not from shared ducts. Air pollution sources are isolated more effectively, improving the overall air quality in a building.

    Forced air systems require a higher heating input to compensate for their inefficient heat distribution. However, this may also dry the air excessively, which is detrimental to air quality:

    • Dust, viruses and other pollutant particles can stay airborne for longer.
    • Dry air can irritate the eyes, skin and respiratory system.
    • When computers and other electronic devices are used, dry air increases the risk of damage from an electrostatic discharge.

    To conserve indoor air quality, ASHRAE recommends a relative humidity of 40-60%. This humidity range provides comfort, while eliminating the negative effects of low and high air moisture. Since underfloor heating operates with less heat input, the drying effect on indoor air is reduced.


    Underfloor heating can improve energy efficiency and indoor environmental quality, by eliminating air turbulence and drafts. Greater savings are possible when the heating system is hydronic, and water is delivered by a high-efficiency heat pump or boiler. By getting in touch with a qualified MEP engineering firm, you can find the best system configuration for your building.

    New constructions provide an excellent chance to use underfloor heating, since the system components can be installed along with flooring and slabs. The installation is more difficult in existing floors, but you can plan the upgrade along with a renovation project to avoid disruption.

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    Tags : Space Heating efficient heating underfloor heating radiant heating radiant floor trench heating

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