Having a Passivhaus Open Day on our doorstep at Lower Chute, members of Transition Town Andover were keen to book places on the tour and find out more about this low carbon house. As we approached the house the striking feature was the two storey window in the otherwise traditional style house looking completely at home in the Wiltshire countryside. Lisa Jackson welcomed us to her family home and explained the design and the building process whilst showing us around the roomy modern interior.
Lisa explained that living in the countryside with no mains gas available meant that alternative heating fuels were costly. This motivated her and her partner to look at house designs which minimized fuel usage whilst maintaining a comfortable temperature. Researching the Passivhaus standard shows this works because there is a high level of insulation in an exceptionally airtight building with a mechanical ventilation system which recovers heat to recirculate to all rooms. Lisa explained the orientation of the building is also important to collect heat from the sun. To prevent heat loss high specification triple glazed doors and windows were fitted by specialist installers.
The framework of the house is wood and the whole building is sealed to make it airtight. All services coming into the house had to be designed to keep breaks in the seal of the building to a minimum. The air circulation to each room is carefully controlled by a system using only 40 watts, which recovers heat and recirculates air, though vents, into every room. Two solar thermal panels on the roof supply the hot water and a thermostat shows the temperature reached by the solar panels. At the end of the day the family decides how much they need to top up using an electric immersion heater. A wood burning stove is used in cold weather but due to the design of the house and wood burner two to three logs produce enough heat for the whole house. Solar PV panels have been situated on the garage roof to generate electricity for the house and export to the National Grid.
We discussed whether Passivhaus design could be suitable for all buildings and although it would not be possible to get every new house to this standard many of the specifications could be incorporated into new buildings. The main difficulty would be to get sufficient solar gain through the windows if there was shading from other houses or trees but the amount of heating needed would still be greatly reduced.
For more information on how Passivhaus buildings offer a comfortable temperature whilst achieving a 75% reduction in space heating go to: http://www.passivhaustrust.org.uk/