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Ambient temperature heat networks are increasingly being considered, however, are not recognised to be heat networks by the GLA, thus presenting a planning risk where developments are in heat network priority areas. They designate them as individual heating systems which they say should only be specified where heat networks are determined to be unfeasible – this is unlikely to ever be the case for large dense developments.

Ambient systems come in a variety of forms, but fundamentally involve circulation at low temperature (e.g. 20oC) around a site with water source heat pumps provided at each building or home to generate space heating and hot water. Central heat generation could be from any source. Circulation at ambient temperatures virtually eliminates network heat losses, keeps corridors cooler and allows central heat pumps to be used more effectively. These combine to provide excellent CO2 reductions.

Fundamentally heat networks are infrastructure that distributes heat. Ambient systems evidently do this and are also classified as heat networks by the Government for funding from the Heat Network Investment Project (HNIP). As a heating-only ambient system could still be connected to an external heat supply the reasons for the GLA’s stance on this are currently unclear. Whilst it is, ambient systems remain a planning risk.