Raising the bar
Passivhaus could become the catch-all standard we need to achieve low-carbon housing targets. Bill Butcher reports.
There are more than 20,000 Passivhaus buildings worldwide and the methodology for low-energy building is now finally beginning to gather momentum in the
UK. The handful of Passivhaus certified private domestic buildings are now being joined by several social housing projects undertaken by mainstream contractors: Gentoo in Sunderland (pictured above), Orbit/Wates Living Space in Coventry and Hastoe/Bramall Construction in Essex.
A number of non-domestic buildings have also been certified, including the Canolfan Hyddgen training centre in Powys by JPW Construction, a Centre for Disability Studies in Rochford, Essex, by Simmonds Mills, the Beechwood Park office development in Dover, built by Van Developments for property developer WCR, and several Passivhaus schools in the pipeline in Leeds and Exeter.
Passivhaus building products are increasingly available to the supply chain. For instance, the Green Building Store introduced a range of specialist Passivhaus products last year. Training in Passivhaus design and the Passivhaus Planning Package (PHPP) software are becoming more widely available through the Association for Environmentally Conscious Building (AECB) and Stratchclyde University. There are also now several Passivhaus certifiers in the UK, including BRE, Inbuilt, the Scottish Passive House Centre and WARM.
So why this sudden surge in popularity in the UK? After all the eco bling and greenwash, the confusion of “zero-carbon” goals and Code for Sustainable Homes requirements, perhaps this is finally a standard we can get our teeth into. Passivhaus design offers a radical solution to cutting buildings’ carbon emissions, and producing high-quality, comfortable buildings that use 90% less energy for space heating than the UK standard.
Passivhaus is a quality-assured standard and methodology for low-energy building developed in Germany in the 1990s. Based on well-researched and proven building physics, Passivhaus is based on the principle that reducing heating loss to a minimum is the most robust – and cost-effective – way of achieving a low-carbon building.
The Passivhaus Institut in Germany has developed the PHPP software which can accurately model a building to Passivhaus standard and predict space heating need and energy consumption.
The key features of Passivhaus buildings are:
Super-insulation: U-values less than 0.15W/m2K
Windows: Whole window U-values not exceeding 0.80W/m2K
Airtightness: Air leakage less than 0.6 air changes per hour @ 50Pa (for houses, this is generally equivalent to an air permeability of less than 1m3/m2/h @ 50Pa)
Ventilation: over 80% heat recovery from ventilation exhaust air, using an air-to-air heat exchanger
Total energy demand for space heating and cooling less than 15kWh/m2/yr
Total primary energy use for all appliances, domestic hot water and space heating and cooling less than 120 kWh/m2/yr
Passivhaus could become the best and most reliable approach to low-carbon building. Poorly modelled in the Standard Assessment Procedure (SAP), the industry is building so-called “low-energy” and “zero-carbon” buildings with no independent verification of those claims.
Now there is a growing call in the UK to integrate Passivhaus standards into targets for zero-carbon buildings through the energy elements of Code for Sustainable Homes and BREEAM, as well as upcoming revisions of the Building Regulations. This will, at the very least, mean significant changes to the Code and upgrading SAP to make it as accurate for low-energy buildings as the PHPP.
The Passivhaus standard and methodology also has an important role to play in retrofitting existing buildings. The Passivhaus Institut is in the process of developing a refurbishment standard with a still rigorous, but somewhat more lenient, space heating requirement – in recognition of the difficulty of reaching the Passivhaus standard for refurbishments.
The Passivhaus standard requires quality assurance of materials and construction methods on site. For the Passivhaus approach to flourish in the
UK there needs to be a sea-change within the UK construction industry both in terms of training but also in terms of contractual arrangements.
The industry’s default position of shifting responsibility for quality and cost to the subcontractor is not conducive to the levels of performance needed for Passivhaus. The entire design and building team need to understand why care is needed at every stage of the build and to understand, for example, what happens when the airtightness barrier is punctured.
For this reason, I am in favour of partnership contractual arrangements, as is more usual on complex projects. And on site, appointing an “airtightness and thermal bridge” supervisor to oversee all trades is one way that any size of project could implement Passivhaus.
I believe the Passivhaus standard needs to be urgently adopted as a target for all new buildings and that the Passivhaus methodology should also be considered for refurbishment projects. At the recent Passivhaus conference in Dresden I was impressed with the maturity of the methodology – it has been applied to everything from kindergartens to laboratories. There is no need to reinvent the wheel – the Germans have already invented it, nearly 20 years ago.
Bill Butcher ICIOB is director of the Green Building Store and project leader on the UK’s first cavity wall Passivhaus at Denby Dale, Yorkshire. CM readers can register for free technical briefing on the project at: www.greenbuildingstore.co.uk/denbydalehouse
Tips of the Trade
Specifying low-energy lighting
Select the right lamp
What is the lamp is going to be used for? Where is the lamp being installed? What kind of light source/light output do I want? Once these questions are answered, it is easy to identify the perfect energy efficient replacement, whether it is a standard fluorescent, compact fluorescent light (CFL), low energy halogen bulbs or long-life, high-efficiency LED lamps.
Ensure it’s energy efficient
EU legislation is enforcing the removal from the market of the most energy-inefficient lighting products over the next few years. Avoid getting caught out – The Lighting Association or the Lighting Industry Federation can provide full details.
Keep up with technology
The technology behind low-energy CFL bulbs has advanced rapidly and lighting manufacturers now offer variants that cast the same warm glow as incandescent tungsten bulbs, and the option to dim lighting levels. Products that mimic natural daylight – with a higher proportion of “blue” light – are also available.
Many manufacturers have created highly efficient LED retrofit lamps, modules, and luminaires which can be used in virtually any application for general illumination. Significantly, LEDs require very little power to achieve high light output so it is possible to reap energy savings of up to 80% compared with traditional lighting products.
Be aware of the statistics
Artificial light accounts for around 19% of global energy consumption so there is huge scope to reduce carbon emissions by switching to more efficient lamps and lighting controls.
Dave Ellis, national sales manager – specification at OSRAM
Cement products sold by Cemex in the UK now feature carbon labels that detail the amount of carbon dioxide produced during their entire lifecycle. The Carbon Trust’s Carbon Reduction Label details the cement’s carbon footprint, including the amount of CO2 and other greenhouse gases generated by its production, covering the extraction of the raw materials, to manufacturing, distribution, use by customers and disposal at the end of life. The cements generate between 17kg to 24kg of CO2 per 25kg bag, depending on the product composition, says Cemex.
Unsightly hoardings have been replaced by verdant green living walls at the site of the new Library of Birmingham. The 5m-high hoardings will feature a LivePanel living wall covering the top 2.2m, planted above a 2.8m layer of Green Screens, a robust ivy-covered metal fencing designed to stop vandals and fly posters from damaging the hoardings. Both products are supplied by Mobilane, and were installed by Hedera Screens. The modular LivePanel system will feature various plants in a specially-developed substrate layer that encourages the plants to take root and thrive.
VarioWIN is a compact biomass wood pellet boiler designed for residential applications with a low-energy demand. The boiler has an output range of 3.6kW to 12kW and can be adapted to accept either direct pellet feed, pneumatic suction or manual fuel loading. All the heating components are mounted inside the boiler, eliminating the need for a boiler room. VarioWIN will enable homes to meet level 4 of the Code for Sustainable Homes, says manufacturer Windhager.
It qualifies for financial support through the Renewable Heat Incentive scheme, due to arrive in April 2011.