An existing house on the site (see photo) was comprehensively refurbished and extended incorporating a series of sustainable strategies to keep the owner's carbon footprint low whilst producing an up to date house which sits comfortably within the conservation area in this small village on the outskirts of Cambridge.
The existing 1960s house was retained to reduce the amount of 'embodied energy' which would have been required to replace the existing structure and fabric. The existing building's wide foundations were used to support a new external skin which included an additional 100mm of insulation behind a new timber cladding. A new roof structure and covering provided the opportunity for increasing the insulation of this element which was further enhanced by the use of taped membranes behind the inner surfaces to reduce heat losses through nooks and crannies in the construction.
A wood pellet boiler was selected as the heat source for the building as it is notionally regarded as being carbon neutral, fully renewable as the fuel is produced both from the waste products of timber industries (furniture, joinery, timber production etc) and directly from sustainable forests for pellet production. The pellet boiler is housed in a studio area of the carport with a hopper which is filled twice a year by a pellet tanker. Having created a well insulated and well-sealed shell, the next most important thing is to ensure that the heat which has been created is not then lost through extract ventilation to deal with the inevitable stale air which the insulating and sealing of the building inevitably creates. To tackle this problem, Mechanical Ventilation with Heat Recovery (MVHR) has been introduced taking the heat out of the stale air which is continuously extracted from the bath, shower, kitchen and boiler room and puts this heat back into the cooler air which is continuously introduced from the outside.
A two storey conservatory lets sunlight and warmth into the centre of the home and internal windows into this space allow the heat generated to pass into the north facing side of the house. The conservatory is fitted with an electrically operated external blind to keep the sun off on very hot days and a large roof vent operated manually by a rope and 'jammer' to let surplus heat out of the whole building using the 'stack effect' of rising hot air to vent surplus heat out of the common areas of the house. The conservatory links the north and south sides of the dwelling and creates the opportunity for cooling across the house in hot summers.
The hot water system is fired solar panels on the south side of the building in the summer months and is supplemented by the pellet boiler in the winter.
A 3,500 litre tank was installed under the patio which collects water off 50% of the roof area and is used for supplying all of the WCs with water for flushing as well as the washing machine