Low-temperature heating is a heating system that warms a space using flow water of no more than roughly 55 °C, instead of the 70 to 90 °C a traditional radiator installation runs on. To deliver the same amount of heat with cooler water, the system needs a far larger emitting surface.
Why lower?
Heat pumps, district heating networks and solar thermal systems deliver heat most efficiently at a low temperature level. The lower the required flow temperature, the higher a heat pump’s coefficient of performance (COP). A condensing boiler also performs better the cooler the return water is, because only then does it genuinely condense. Low-temperature heating has therefore become the standard for energy-efficient and fossil-free buildings.
Forms of emitter
- Underfloor heating — the most common form. Large area, low temperature, comfortable radiant heat.
- Wall and ceiling heating — useful where the floor cannot be opened up.
- Low-temperature radiators and convectors — deeper, taller, or fitted with a quiet fan so they still produce enough output at low water temperature.
Application
The first condition is a well-insulated building envelope: roof, wall and floor insulation, high-performance glazing and airtight detailing. In a poorly insulated house a low-temperature system simply will not reach the target temperature on a cold day.
Points to watch:
- Calculate room by room. Each room’s heat demand determines the emitter area needed. A single room that cannot keep up — often a loft room or a room with a lot of glass — sets the flow temperature for the whole system.
- The floor finish matters a great deal. Tiles and poured floors conduct well; thick carpet or a heavy underlay beneath laminate acts as insulation and costs output. Look at the thermal resistance of the finish.
- Larger pipe diameters. With a smaller temperature difference, more water has to circulate. Undersized pipework is a common mistake when retrofitting.
- Hydraulic balancing. Without balancing, water takes the shortest route and distant rooms stay cold.
- A slow system. Underfloor heating responds slowly; work with a steady base temperature rather than a deep night setback.
Related terms
- Boiler
- Radiator
- Convector
- COP value
- Insulation
- Energy saving
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