(This article was first published in 2008)
In 2007 Gordon Brown announced plans for ‘Eco towns’ with 100,000 new carbon neutral (or zero carbon) homes. His pledge followed the announcement at the end of 2006 by secretary of state for the Department of Communities and Local Government (DCLG) Ruth Kelly to make all new homes ‘carbon zero’ by 2016 by introducing the ‘Code for Sustainable Homes’.
While the government is to be commended for its commitment to lowering carbon emissions and reducing their impact on the environment – houses account for 30% of the UK’s total CO2 emissions – upon closer investigation, it could be suggested that the idea of building “zero carbon” homes by 2016 in the UK is, in fact, unrealistic.
The problems
• The first problem presented by the “zero carbon” home is that, because the generation of renewable energy is relatively unpredictable, it is unlikely to coincide with peak demand. As a consequence, “zero carbon” homes still use electricity derived from fossil fuels, meaning that they still produce carbon emissions. This result is these homes are not zero carbon, but a low carbon building instead.
• A second problem is that whilst people could attempt to offset this with carbon-free electricity generated from renewable sources, at present renewables account for only 3% of electricity nationally. This means that to build zero carbon homes, new renewable power stations need to be constructed.
• A third problem is that two Government departments have differing definitions of what constitutes a “zero carbon” home. The Treasury definition states that a gas supply can not be used in a “zero carbon” home whilst the DCLG, via the Code for Sustainable Homes, suggests that gas supply is acceptable. To determine which is the most appropriate definition is not as easy as it may seem.
• The fourth problem is that the generation of renewable energy is expensive, the costs are expected to fall as the manufacturing technologies improve, but for now it does not represent the most economic alternative.
PassivHaus
The Passivhaus standard, developed in Germany, reveals just how far behind certain European countries we are in the advancement of energy efficient buildings. The premise is simple, it relies on very high levels of insulation, super-insulated openable windows and a well sealed building fabric to reduce energy consumption.
It’s mechanical ventilation system provides excellent air quality as well as a highly efficient ‘heat recovery’ system, meaning that the house retains heat from activities like cooking, watching television and showering and uses it to heat the building which as a result, tdoes not need a central heating system.
When you combine all these measures together, compared to the average house, a Passivhaus reduces CO2 emissions by 80% and energy consumption by 85%. Considering heating and hot water accounts for 60% of the energy we use, these measures have a significant impact on the environment.
Should we adopt the Passivhaus model for building in the UK, it would meet many of the requirements of the government’s Code for Sustainable Homes (CSH), in fact early estimates suggest that Passivhaus projects could gain a rating of Level 4-6 (Level 6 being the best). When you consider that housing associations will not receive government funding if their rating is 3 or below, meeting the CSH is crucial.
There are currently no homes in the UK that meet Passivhaus standards, and whilst architects and builders are learning skills to meet the anticipated demand, there is a long way to go.
Solutions like Passivhaus offer a more efficient and realistic answer to reducing CO2 emissions than the government’s current plans to offset carbon rich energy by emphasising renewable energy technologies.
The knowledge gap
Perhaps more importantly they reduce energy consumption as a whole thus avoiding complications arising when a renewable technology fails or breaks down. But to assume that builders, architects and others in the construction industry will be able to construct such homes in 9 years time is a stretch as new skills will be needed. Over the last nine months we have been steadily researching how to design and construct projects to the exacting Passivhaus standard. Designing and constructing buildings to the Passivhaus standard also requires a leap of faith and vision from developers, again our research reduces the size of the leap required.
If Mr. Brown is to realise his Eco-Town dream within the allotted timescale then the UK construction industry as a whole needs massive government funded internal investment so that it may learn lessons from its European counterparts. Failure to invest in this manner will mean that a few innovative companies will be charged with developing the skills and slowly leading a revolution in how we design and build.
About the author:
Mark Siddall, principle at low energy architectural practice LEAP, is an architect and energy consultant specialising in low energy and PassivHaus design. He was project architect for the Racecourse Passivhaus scheme and has a keen interest building performance. In addition to architectural services his practice provides project enabling and education for clients, design teams and constructors.
LEAP website: www.leap4.it