This Paxton Locher home scheme in Primrose Hill, north London, follows the practice's award-winning Clerkenwell house. Here, thermal mass stays in the ground; lightweight materials, including a prefabricated hooped steelwork structure, respond to a tight site. The scheme incorporates what are probably the first geothermal piles built in the UK: heat transfer pipes have been cast within the reinforcement cage of the pile structure (25 piles in 12 days). An earth battery acts as a buffer to heating and cooling peaks and troughs, with heat transferred via a geothermal water-to-water heat pump feeding underfloor heating coils at every level. Standard underfloor components combine with liquid-applied plastic roof membranes to create a heat exchanging roof; solar panels provide power for the building and most daytime pumping requirements. Rainwater and greywater is collected and stored in underground tanks.