Housing is responsible for more than a quarter of the UK's carbon dioxide emissions. But from 2016, all new homes must be built to Level 6 of The Code for Sustainable Homes. This means that during their life they must remove more carbon dioxide than they release into the atmosphere. This presents the construction industry with a considerable challenge.
Effectively making new homes a carbon sink is likely to require microgeneration of electricity and heat from wind or solar technology. However, significant carbon savings can also be made by using renewable materials in construction, which have far less embodied carbon (the carbon used to make any product, bring it to market and dispose of it) than their non-renewable alternatives.
Are renewable materials practical?
In 2009, at a site near Watford, the UK's National Centre for Biorenewable Energy, Fuels and Materials (NNFCC) embarked on an ambitious project to build one of the UK's first homes made to Level 4 of the Code using only renewable or recycled materials.
The Renewable House was built to demonstrate how an environmentally friendly and highly energy-efficient, three-bedroom, detached family home could be built for 10 per cent less than the cost of a conventional house of the same size and code. This saving was thanks to a shorter build time, less need for heavy lifting gear and a smaller waste footprint.
The house was made using hempcrete (a mixture of hemp and lime) and timber frames, insulated with sheep wool, triple glazed and tiled with recycled slates. These materials offer innovative energy- and cost-saving features and it has been estimated that The Renewable House's carbon footprint is about 20 tonnes lower than a traditional brick-and-block house; the equivalent of nearly 20 return flights from London to New York.
And this month (revealed here for the first time), the NNFCC has appointed Home Grown Homes UK Ltd to undertake a retro-fit of The Renewable House and re-launch it as a Code Level 5 home at INSITE 2011 – BRE's biannual exhibition – to further demonstrate the potential of renewable construction materials.
Building new renewable homes
Following the success of the home, the UK government has invested £6.7m – from the Low Carbon Investment Fund – to build more than 300 new, affordable homes based on The Renewable House model. These are due to be finished this year. The government scheme aims to demonstrate the viability of these materials and act as a spur for the renewable construction industry. It also hopes to engage the affordable housing sector in the low-carbon agenda.
To explore the sustainability of these properties, their performance will be monitored over the next 12 months. For example, the rooms will be tested for air quality and temperature control, and any problems with maintenance and durability will be recorded. Preliminary NNFCC results from the original Renewable House estimate that renewable materials can save a third on an average household energy bill.
The NNFCC's materials manager, Dr John Williams, says: "Renewable materials offer an affordable solution to meeting some of the key environmental demands required by the government for new housing developments. We need to look carefully at their sustainability to ensure the evidence is there to support the construction of even more renewable homes."
Future of renewable housing
Renewable materials clearly have potential, but do we in the UK have the resources to sustain the industry? For example, is planting hemp for housing a justifiable use of the UK's precious agricultural land?
Some would say yes, as Dr Williams explains: "Growing hemp is a popular option for farmers as it is a good break crop for wheat. And if just a little over one per cent of the UK's agricultural land was used to grow hemp, it would be enough to meet the UK target to build a quarter of a million new homes every year between now and 2020."
However, future government policy on new housing remains unclear and the National Housing Federation has suggested that this target could be scrapped as a result of the government spending cuts. But it is clear that renewable materials have a crucial role to play in building the low-carbon homes of the future.
Dr Matthew Aylott works for the NNFCC, the UK's National Centre for biorenewable energy, fuels and materials