This innovative house extension in Northcote uses both planning constraints (through the building envelope) and the path of the sun to generate a subtracted barn-like form at the rear of an existing weatherboard house. The subtracted sun path enables the rear garden and outdoor living area to enjoy direct sunlight, correcting the inherited orientation of the house. The rear façade is a sustainable artificial timber screen system used for sunshading, balustrading and view screening. The side walling is treated like a roof on the above ground level.

The house design process involved the application of a parametric subtractive solar technique called “Subtracto-Sun” developed for maximising daylight amenity preservation. The client’s brief required the increase in size of an existing dwelling by adding a living area, two new bedrooms and attic space without losing sunlight to the back garden area. A digital model was created for the maximum permissible envelope under local planning regulations and the Subtracto-Sun technique was employed to sculpt the envelope to ensure maximum solar access to the nominated garden space during a designated time period.