Climate & Cities
Heat Pumps In Cities Run Into The Space Outside The Flat
The technology works in dense housing, but the equipment needs an outdoor position, a route for pipes and a place for a tank, and apartments rarely have any of them.
Replacing a gas boiler in a house is largely a plumbing exercise. Doing the same in an apartment runs into questions of space, ownership and noise that the technology cannot answer.
The outdoor unit needs a position nobody owns
A heat pump exchanges heat with outside air, so part of the system must sit outdoors with clear airflow around it.
In a flat, the available outdoor surfaces are balconies, facades and roofs, which are usually common property rather than part of the home.
Consent for a unit on a shared surface therefore involves the building's management, and refusals are common where the facade appearance is controlled.
Low flow temperatures need larger emitters
A heat pump runs efficiently when the water circulating through the system is cooler than a boiler would supply, which means each radiator delivers less heat.
Compensating requires larger radiators or underfloor systems, and both take space or floor build-up that an occupied flat may not have.
Improving the fabric reduces the demand instead, but that returns the problem to the collective decision about the building's envelope.
Hot water storage returns to the plan
Combination boilers removed the cylinder from many homes, and the space it occupied was absorbed into cupboards, bathrooms and kitchens.
A heat pump generally needs that cylinder back, because it heats water steadily rather than instantly on demand.
Finding a location for a tank in a flat designed without one is often the decisive practical constraint, more than the equipment outside.
Noise limits the placement further
The outdoor unit contains a fan and a compressor, and although the sound level is modest, it is continuous and closer to neighbours in dense housing.
Permitted development rules typically set a noise limit at a neighbouring window, which restricts where a unit can go on a tight urban plot.
Several units on adjacent balconies raise the combined level, so a building that approves one installation may struggle to approve the twentieth.
Shared systems avoid the individual problem
A single large heat pump serving a whole building removes the need for equipment at each flat and puts it in a plant room instead.
That requires a distribution network within the building and a billing arrangement, which is straightforward in new construction and intrusive as a retrofit.
The choice between individual and communal systems is therefore made by the building's existing pipework and governance rather than by comparative efficiency.
Questions readers ask
Do green roofs save energy?
Modestly, and mostly on poorly insulated buildings. On a well-insulated roof the thermal effect is small. Run-off attenuation is the benefit that reliably justifies them.
Are green roofs maintenance free?
No. They need outlet clearance, occasional weeding and inspection, and they need access to do it. Most failed installations were neglected rather than badly built.
