Cranmer Road, King's College, University of Cambridge

The buildings use electricity as their sole energy source, which aligns with the ongoing decarbonisation of the electricity grid. Mechanical systems are decentralised, with point of use space heating and instantaneous domestic hot water generation, to limit distribution losses. Waste water heat recovery and low flow showers limit the energy required for hot water, and mechanical ventilation with heat recovery (MVHR) is used to limit heat loss and ensure good air quality year-round.

The summer comfort strategy has a combination of automatic bypass of the heat exchanger on the mechanical ventilation units, and openable windows. The design uses simple, standard components in systems that were easy to commission and should be simple to maintain.

The buildings achieved airtightness results three to four times better than the Passivhaus limit, more than 50 times better than building regulations allow. Measured peak heating demand has been 8 W/m², lower than the Passivhaus target of 10 W/m².

We provided a simple building user guide for every student, so they could understand the background of the building and how to interact with it to achieve comfort in a low-energy way.

Reviewing the operational energy consumption allowed a sense check to understand if the services and systems were operating as intended and target areas for improvement, with the analysis helping to demonstrate that the building generally aligned with the modelling.

Carrying out an occupant survey allowed both energy use and occupant feedback to be brought together to ensure that very low energy consumption wasn’t being achieved to the detriment of occupant satisfaction and comfort.