energy efficient building

The Passivhaus Standard


The Passivhaus standard offers a well-established alternative to the Code for Sustainable Homes and the Building Regulations for sustainable design and construction. Denise Freeman investigates the emergence of Passivhaus in the UK and the benefits of external wall insulation and modern render systems. The term Passivhaus relates to the rigorous energy-efficient building standard developed in Germany in the late 1980s. Although it is considered to be a relatively new standard in the UK, Passivhaus is widely used throughout Europe. 17,000 buildings have been constructed using its design principles. The core focus of Passivhaus design is to achieve an extremely low-energy building that requires little energy for space heating and cooling. Buildings built to Passivhaus standards typically achieve a 44% reduction in carbon emissions compared to an average existing home.

Passivhaus is sometimes confused with Passive House, which typically relates to a building with traditional passive design features, such as the use of solar gain. Whilst Passive House design relies exclusively upon the orientation of a building and format, and uses fewer or no active mechanical and electrical systems. A Passivhaus building integrates some passive design features, but takes an active approach rather than a passive approach. In essence, the fundamental space-heating requirement in a Passivhaus building is managed by a mechanical ventilation and heat recovery system. This active approach also allows the Passivhaus designer to be more flexible with the building design. Current legislation stipulates that new build homes should achieve a minimum of level 3 under the Code for Sustainable Homes. However, this is soon set to increase with all new builds having to comply with code level 4 by 2013. Passivhaus is equivalent to code level 4. The sustainable methodology behind Passivhaus brings the housing sector a step closer to the government's zero-carbon idea, which is almost impossible to achieve without implementing Passivhaus principles.

Core Elements

A Passivhaus building must incorporate a number of core elements including exceptional levels of insulation, an airtight envelope, a heat recovery system and thermally advanced windows and insulated doors. In order to realise the extremely high levels of thermal performance that the Passivhaus standard requires, the external walls must achieve a U-value rating of <0.15W /m2K. This is achieved through the use of an external wall insulation (EWI) system. EWI systems are increasingly becoming a key element in the specification process with regards to high thermal efficiency requirements. Around 30% of the energy used to heat a typical home is lost through the external walls. EWI systems work by wrapping the building in a thermally efficient envelope, significantly reducing any energy loss. maximised and comfortable internal maintained all year round.