Wood and Passivhaus

[edit] Introduction

Buildings often underperform when it comes to energy efficiency. On average, traditional new-build homes use 60-80% more energy for heating than their design target.

The UK government’s Industrial Strategy has set out some ambitious targets via the Construction Sector Deal and the Clean Growth Grand Challenge with a mission to halve energy use in new buildings by 2030. The methods to achieve this include developing innovative energy and low carbon technologies to reduce cost, coupled with quality-controlled construction techniques.

A proven and tested energy performance standard that fulfils the government’s aspirations is Passivhaus. A German concept developed in the early 1990s, and adopting passive design principles, Passivhaus achieves impressive energy efficiency as it bypasses the need for traditional heating and cooling systems.

[edit] Creating a healthy environment

Passivhaus is about airtightness and breathability. Choosing the right insulation material is key.

The welcome long-term side-effects of Passivhaus performance include improved indoor air quality, thermal comfort, and self-maintained moisture and humidity levels. Homes designed to Passivhaus standards often benefit from increased space and daylight too.

[edit] The affordable solution

Passivhaus is widely seen as an option reserved for self-builders, but this couldn’t be further from the truth. Many local authorities and housing associations are now building to Passivhaus standards for their own housing schemes, offering the benefits of this approach to their tenants.

Take for example Heathcott Road. Based in Leicestershire, this unassuming housing estate is in fact one of the largest affordable Passivhaus housing schemes in the country. The once disused and overgrown 13.2 acres of land has been regenerated into a £7 million community made up of a permaculture farm and 68 eco-homes that have been built to Passivhaus standards.

Designed by architects rg+p, the scheme addresses the needs of the local people by providing homes with one to four bedrooms, constructed using Westleigh Partnership’s Westframe PassiPlus timber framing. As a result, the homes achieve U-values as low as 0.1W/m2K.

This is an affordable solution for individuals and families who can look forward to a future of very low to zero energy bills. The homes have been built to Lifetime Homes Standard making them adaptable to residents’ needs throughout their lifetimes. In addition, the use of timber frame made the homes more cost-effective to build.

It’s a trend that’s catching on and other social housing and affordable home schemes built to Passivhaus standards include:

• Architype’s affordable housing project, Much Wenlock, in Shropshire, also using timber frame;
• Mole Architects’ small development on Hindolveston Road in Norfolk, using locally sourced timber boards;
• Lancaster Cohousing’s eco cohousing community in Forgebank, another of the largest Passivhaus scheme’s in the UK;
• Gentoo’s bungalow scheme on the Racecourse Estate in Sunderland that helps older people fight fuel poverty; and
• MH Architects’ scheme in Standings Court, West Sussex, which is a 100% affordable rented site.

[edit] Building offsite

Other goals for construction outlined in the Industrial Strategy include modular technology for building offsite. An example of this is Tectonic Architects’ Passivhaus built using cross-laminated timber (CLT) in Hackney, making it the first certified Passivhaus homes in the borough.

Hackney is a built-up area. The urban infill site presented challenges with its conservation area location which receives no south-facing sun. Combatting limited site access and reducing disruption to existing neighbours, the use of CLT meant the structure could be constructed in just two days before being insulated with wood fibre. The result is a surprisingly light-filled building with a stable temperature and good air quality.

[edit] Powerhouse: The future of Passivhaus?

Powerhouse is a new and upcoming standard. It’s a Norwegian benchmark for which the building must produce more renewable energy over its lifetime (typically 60 years) than it uses during its entire lifecycle. This includes construction, operation, future renovation and demolition. The building needs to achieve Passivhaus standard first, but Powerhouse takes it to the next level with a focus on energy generation, demonstrating how the standard is evolving to incorporate the circular economy.

--Wood for Good

[edit] Related articles on Designing Buildings Wiki

• An Introduction to Passive House - review.
• Code for sustainable homes
• BREEAM.
• Fabric first.
• Home Quality Mark.
• Leadership in Energy and Environmental Design.
• Passive design.
• Passivhaus.
• Saffron Acres, Leicester, the UK’S largest Passivhaus residential development.
• Sustainability.
• The building as climate modifier.
• Zero carbon homes.
• Zero carbon non-domestic buildings.