Staff and students at the Centre for Alternative Technology’s Graduate School for the Environment have received praise for new research evaluating the environmental impacts of mainstream methods of insulating solid wall homes, and investigating sustainable alternatives. Students Marion Wright, Naomi Miskin, Andrew Flower and staff Ranyl Rhydwen and Arthur Butler were awarded best paper at the prestigious Retrofit 2012 earlier this year.
“Improving the energy efficiency of Europe’s housing stock is crucial in view of climate change,” says lecturer Ranyl Rhydwen. “It is an urgent priority for the government and the building sector.” The international Retrofit conference, hosted in January by Salford University, was set in order to appraise recent research into this area.
30% of the UK’s carbon emissions come from the domestic sector – and with 56% of that coming from heating, improving the energy efficiency of our homes can go a long way toward reducing the impact we have on the environment. And while new legislation will see all new builds be ‘zero carbon’ by 2016, retrofitting existing housing stock remains a priority, as some calculations suggest that retrofitted homes can save up to 15 times as much CO2 as demolishing and rebuilding.
However, even if retrofitting is the greener option, the materials used to renovate buildings are frequently carbon intensive and environmentally detrimental. As the researchers say, “the manufacture of building materials tends to have a high energy input, involve toxic processes and create harmful waste.” Since the majority of the UK’s housing stock requires renovation to improve its thermal efficiency and moisture handling ability, investigations have been on-going at CAT to trial sustainable alternatives that could significantly decrease the carbon cost of a large-scale retrofitting project.
Hemp is considered to have particular potential for its ability to sequester large amounts of carbon, improve biodiversity, improve soil quality, grow well without fertilisers, herbicides, or pesticides, and its capacity to simply be composted at the end of its life.
The CAT team received praise for their work comparing two methods of insulating solid-wall homes – dry-lining, the more mainstream method, and using an insulating hemp render. Their research was the first study to directly compare these two methods in a real-world trial, carried out over 18 months in one of the old slate cottages that form part of CAT’s on-site community. Their research considered the performance and impacts of both techniques, as well as forecasting into the future with the use of a complex computer modelling procedure.
Concerns about the efficacy of dry-lining go beyond considerations of the environmentally un-sound materials it requires the use of – dry-lining has also been thought to increase internal condensation and moisture build-up between walls, leading to rot and frost damage. Finding a better method is especially relevant for the UK’s heritage buildings, many of which are have solid walls.
The study confirmed that dry-lining causes moisture build up in walls, as well as demonstrating that hemp renders are effective at insulating, as well as drying out the external wall and handling moisture well.
Hemp seems set to be recognised as an effective, low-carbon, sustainable solution for retrofitting homes. Research into the use of hemp continues at CAT, with staff and students investigating all its potential uses. Rather than using materials with a “long-term environmental legacy,” in Ranyl Rhydwen’s words, utilising materials like hemp which have the ability to sequester carbon may allow us to off-set emissions from other sectors, or from on-site renewables. Perhaps it’s time to consider a stage further than the ‘zero carbon’ home – the negative carbon home.