Research explores state of UK’s heat distribution systems

The distribution of oversizing of heat distribution systems. Source: BEIS

There is a significant opportunity for hybrid systems to substantially reduce emissions without making disruptive changes to heat emitters in homes, a study has found.

On 12 March, BEIS published research into the state of heat distribution systems in homes, seeking to fill gaps in the current evidence base. It looked at both the state of heat distribution systems in the UK housing stock and measures that could be taken to improve them. The majority (95%) of dwellings were found to have central heating, with 83% running off gas, and nine in 10 (90%) using wet heating with boilers and radiators. A small, albeit growing number are using underfloor heating.

Furthermore, heat distribution systems were found to rarely be hydraulically balanced and often significantly oversized. Neither the design nor commission of heat distribution systems has changed much over time, with just 20% of dwellings undertaking an annual service, something that should be standard practice.

Inefficiencies uncovered include poor hydraulic balancing, reducing performance by 10%, limescale (15%), air (6%) and build-up of sludge (15%). All can be eliminated, or at least significantly reduced, by proper maintenance and commissioning of the system. Thermostatic radiator valves, the performance enhancing measure with the most robust evidence base around it, can offer an energy saving of 3% but further testing and trials were noted as being needed for other measures.

On the suitability of existing heat distribution systems for low temperature heating, it found 10% of UK dwellings could meet heat demand with a 55°C flow temperature and 1% at 45°C on a peak heating day, in the baseline case. On an average winter day, 53% could use a 55°C flow temperature with 6% able to use a 45°C flow temperature with no changes to their heat emitters or flow rates.

It deemed the results significant as they help to quantify the number of dwellings that need changes to the heat distribution system when a low temperature heat source is installed. It signals that there may be a significant opportunity for hybrid systems to be used to substantially lower emissions without any disruptive changes to heat emitters, though further work was noted as being required to verify the results in relation to the “real” output of systems in contrast to their rated output and the true heat demand of occupied properties.