Underfloor heating
Ancient smoke-trench method evolved into modern hydronic and electric systems.
Underfloor heating and cooling is a type of central system that controls indoor climate for comfort by embedding hydronic (fluid-filled) or electric heating elements within a floor. It warms a space through conduction, radiation, and convection. People have used this method since the Neoglacial and Neolithic periods.
Archaeological finds in Asia and Alaska’s Aleutian islands show that early inhabitants dug stone-lined trenches under their floors and channeled smoke from fires through them. The hot smoke heated the stones, which then radiated warmth into the living area. This ancient technique has evolved into modern systems that use either fluid-filled pipes or electric cables and mats.
Modern underfloor systems heat the floor with either electric resistance elements (electric systems) or fluid circulating in pipes (hydronic systems). Both types can serve as the main heating for an entire building or provide localized warmth. Some setups allow individual rooms in a multi-room system to be heated separately, preventing wasted energy. Electric systems only provide heat; if cooling is needed, a hydronic system is required. Both electric and hydronic options can also melt snow and ice on walkways, driveways, and landing pads, condition turf on football and soccer fields, and prevent frost in freezers and skating rinks. Various designs suit different flooring types. Some systems are embedded in a screed beneath the floor covering, ideal for new builds or extensions. Others use self-adhesive panels laid directly on an existing level floor, with pipework covered by a self-levelling screed—a common choice for retrofits.
Electric elements or hydronic piping can be cast into a concrete slab (poured or wet system), placed under the floor covering (dry system), or attached to a wood subfloor (subfloor or dry system). Underfloor heating can also be installed in suspended timber joisted floors, either by using metal plates between joists to transfer heat or by integrating pipework into a specially designed structural floor deck. Some commercial buildings use thermal mass, heating or cooling it during off-peak hours when utility rates are lower. With the system off during the day, the concrete mass and room temperature drift within the comfort range; this is called a thermally activated building system (TABS). The terms radiant heating and cooling are common because rad
- field
- Building technology, thermal comfort
- known_for
- Embedded floor heating and cooling systems using hydronic or electric elements
- earliest_evidence
- Neoglacial and Neolithic periods
- primary_modern_types
- Hydronic systems (fluid-filled pipes) and electric systems (resistance elements)
Lore & Background
Underfloor heating has a long history back into the Neoglacial and Neolithic periods. Archeological digs in Asia and the Aleutian islands of Alaska reveal how inhabitants drafted smoke from fires through stone-covered trenches excavated in the floors of their subterranean dwellings. The hot smoke heated the floor stones, and the heat then radiated into the living spaces. These early forms have evolved into modern systems using fluid-filled pipes or electrical cables and mats.
Reader's Guide
Modern underfloor heating systems use either electrical resistance elements or fluid flowing in pipes to heat the floor. Either type can be installed as the primary whole-building heating system or as localized floor heating. Hydronic systems can also provide cooling, while electric systems are used only for heating. Hydronic systems use water or a water/anti-freeze mix in a closed loop, with pipes made from polyethylene materials such as PEX, PEX-Al-PEX, and PERT. Energy sources include natural gas, propane, coal, oil, electricity, solar thermal, wood, biomass, and heat pumps. Underfloor heating is particularly suitable with heat pumps because it uses lower water temperatures, improving efficiency. Electric systems employ non-corrosive flexible heating elements such as cables, pre-formed cable mats, bronze mesh, and carbon films. They can be installed in thermal mass or directly under floor finishes. Underfloor heating can positively affect indoor air quality by facilitating the use of low-VOC flooring materials like tile, slate, terrazzo, and concrete, and by establishing conditions less favorable for mold, bacteria, viruses, and dust mites.
Did You Know?
- Archeological digs in Asia and the Aleutian islands of Alaska reveal smoke from fires was drafted through stone-covered trenches in floors for heating.
- Hydronic systems can be used for both heating and cooling; electric systems can only be used for heating.
- Underfloor heating is particularly suitable when the energy source is a heat pump because it uses lower water temperatures.
- Underfloor heating can have a positive effect on indoor air quality by facilitating the choice of low-VOC flooring materials such as tile, slate, terrazzo, and concrete.
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