This extension and refurbishment of an Edwardian house in Muswell Hill has created a comfortable, low energy home. The original structure of the property was revealed, its modest beauty celebrated. Energy requirements are reduced dramatically by insulating, triple-glazing and improving airtightness. New additions include a rear extension and a loft conversion. This project aims to be an exemplar for the sustainable refurbishment of a typical terraced home in London, with a constrained budget. Both embodied energy and energy in-use have been considered in depth. Design features include timber structure, triple glazing, a continuous airtight layer and insulation to the entire building envelope. Walls were insulated externally at the side and rear, and internally at the front with wood fibre. Insulating internally at the front has allowed the original Edwardian facade to be preserved. Masonry nib walls were retained at ground floor to avoid energy-intensive steel box frames. Natural materials including stone, timber and lime plaster were used throughout rather than cement-based products. The rear extension was built in highly insulated 172mm SIPS and all existing building elements achieved a Passivhaus standard U-value of 0.15 or better. An MVHR system provides pre-heated fresh air, creating a warm and comfortable home. The system also filters the incoming air, removing pollen, diesel particulates and NOx to create a healthy indoor environment.