Passivhaus design standard
The dwelling has been built to the Passivhaus standard, working through PHPP design with Andrew Lundberg of Passivhaus and with initial M and E designs by Alan Clarke. As most readers will know, this is a successful European ultra-low energy standard for buildings as Passivhaus buildings use only a fraction of the energy for heating (90% less) compared with houses built to the standards required by current UK Building Regulations, and deliver low-carbon solutions without needing excessive renewable energy. Where Passivhaus differs from UK Building Regulations and CSH, is the requirement for an absolute minimum level of energy consumption instead of improvement over a more basic specification.
The Passivhaus approach has three main strands:
- To minimise heat loss – via a compact built form, super insulation and triple glazing.
- To minimise ventilation heat loss – via airtight construction and heat recovery ventilation.
- To optimise solar gain for winter heat.
These factors combine to deliver a heating demand that can be met with a minimal heating system (it is recognised that to design a house that needs no heating at all is not economic). As well as very low heating bills, Passivhaus offers comfort and a healthy indoor environment. Attention to detail in design and construction ensures no draughts or cold spots wherever you are in the house. Heat recovery ventilation uses low power fans to provide ample fresh air day and night, warmed to room temperature by a heat exchanger transferring the heat from the exhaust air from kitchen and bathrooms to the incoming air.
Passivhaus is a rigorous energy standard; where energy performance must be demonstrated through the use of the Passivhaus energy modelling software, (PHPP) which is specifically designed to model ultra-low energy buildings. This is backed up by air leakage tests and commissioning records of the heat recovery ventilation. The standard requires a predicted heating demand of 15kWh/m².a over the usable floor area, adapted for the local climate (average energy use for UK housing stock is around 200kWh/m².a and new-build ranges from 50-100kWh/m².a).
