Heat Pumps for Public Buildings: How to Assess a Site Before Procurement

The right type depends on loads, site and operating pattern rather than on the building category alone. A school with sharp hot-water peaks for showers and a part-time occupancy schedule often works well with an air-source heat pump, a storage tank and load-based control. A hospital, which needs heat, hot water and often cooling around the clock, may justify air-source or ground-source plant with redundancy. Decisive factors include available space for outdoor units or boreholes, electrical supply capacity, acoustic limits and the required delivery temperature, so an engineer should confirm the choice after load calculations.

Yes, but only if their heat output is sufficient at the lower flow temperatures a heat pump uses, typically 35–55 °C instead of 70–80 °C. The room-by-room heat-loss calculation is compared with each radiator's output at the new temperature; where output is short, radiators are replaced or supplemented, or heat loss is cut with insulation. Some buildings also need hydraulic balancing. Skipping this check can leave rooms cold in winter or force the pump to run at high temperature with poor efficiency.

Electrical demand depends on the heat load and the pump's coefficient of performance: a heat pump typically consumes roughly 0.2–0.35 kW of electricity for every kilowatt of heat it delivers, but the exact figure varies with operating conditions. A building needing, say, 80 kW of heat may draw on the order of 20–30 kW electrically. The incoming supply, switchboard, cable and grid-connection capacity must be checked before purchase, because reinforcing power is a frequent hidden cost. Final numbers should come from a project calculation, not an average estimate.

Ground source tends to suit sites with land for boreholes or collectors, suitable geology, and a need for stable, efficient operation through cold winters. Air source is simpler to install and cheaper, but its output and efficiency fall as outdoor temperature drops, so a colder climate demands more reserve capacity. The decision follows geological surveys, load calculations and a whole-life cost comparison that includes drilling expense and permits; a project engineer should weigh these factors before the tender.

In buildings with high hot-water use, the heat pump is paired with a storage tank, and water is stored and supplied at a temperature that prevents growth of legionella and other bacteria. The designer sets tank volume, storage temperature and the circulation scheme accordingly, sometimes adding a reheating stage or periodic tank pasteurisation. Exact temperature and operating requirements come from the applicable standards and health rules for the jurisdiction, so they should be written into the design brief and verified at commissioning.

Heat pumps do not behave like boilers: real-world efficiency depends on a chain of decisions from design and sizing through installation, commissioning and daily use. Two systems that both meet minimum standards can still differ because of wrong sizing, poor emitter matching, unbalanced hydraulics, inadequate commissioning or occupants who cannot operate the controls. This is why guidance increasingly recommends buying outcomes—clear comfort, efficiency and running-cost targets, evidence of installer capability, and in-service monitoring—rather than procuring equipment against accreditation alone.