Passivhaus Apartments, Cambridge

The Passivhaus approach will reduce fuel bills to mitigate fuel poverty on behalf of the residents, with expected energy savings of 70-90% compared with standard UK housing construction.

The building has been designed to the five key principles of Passivhaus construction:

+ Airtight construction.
+ Mechanical ventilation with heat recovery.
+ Super insulation of the thermal envelope.
+ Minimal thermal bridging.
+ Triple glazed Passivhaus accredited windows.

The form is simple in line with Passivhaus design principles, to minimise the Form Factor (Thermal Envelope Area / Treated Floor Area) for thermal efficiency. This also reduces the amount of construction materials and embodied carbon.

The south façade has generous balconies overlooking a shared garden that provide both private amenity space and solar shading. The north side of the building has gallery access to the front doors. The external balcony and access structures are separated from the thermal envelope to minimise thermal bridging.

The building is aligned east-west, with a strong north and south orientation, making the energy balance easier to control. Large windows to the south with solar shading allow winter heat gain and small windows to the north optimise the amount of insulated façade. The east and west gables are blank as these faces are harder to control in terms of energy balance.

A pitched roof with external gutters avoids internal rainwater pipes that would conduct heat out of the building. The projecting eaves shade the upper windows and provide a south facing slope for photovoltaic solar panels. Rainwater drains into water butts for irrigation of the garden, which also includes a large swale to the south, to help stabilise water run-off.

Low-embodied carbon construction options include timber framing, a CLT roof, and re-used standard steel sections for the balconies. The material palette of black sinusoidal cladding, zinc and galvanised steel references a southern English rural aesthetic.

Collaborators:
Building Services and PHPP - Max Fordham
Landscape Architect - Jamie Buchanan Landscape
Passivhaus Consultant - Peter Warm Associates
Planning Consultant - Eclipse Planning Services