How new straw-bale homes could help solve the housing crisis

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Posted Mar 31 2015 by Elisabeth Winkler of Lowimpact.org

In an ordinary street in Bristol, UK, something extraordinary is happening.

All of the seven houses are made with straw.

Built from carbon-capturing, renewable materials of timber and straw, the homes bank more carbon than is emitted in making them.

In addition, the negative-carbon homes have received crucial industry certification. Having the BM Trada’s Q mark makes them the first commercially-available straw bale homes in the UK because they are mortgageable and insurable.

This means that straw – a home-grown and low-impact building material – is now a viable way to tackle the UK’s housing crisis.

Making sustainable housing accessible to the public was important to the developer, Martin Connolly.

straw bales on lorry

Building materials on the way from farm to factory.

Concern for homeless and climate change

A social landlord providing emergency accommodation and food for homeless people since the 1980s, Martin Connolly’s family company was awarded 2009 Environmental/Conservation Development of the Year for flats made of solid-wooden blocks, a first for Bristol.

“We got into straw bale housing out of concerns for homelessness and the environment,” he says..

Martin’s vision of affordable low-impact housing led him – after a worldwide search – to ModCell on his doorstep in Bristol, after seeing the eco-design company featured on TV’s Grand Designs.

“Our vision was natural, non-toxic house building which stores carbon. ModCell was the first design we saw that did not use plasterboard which is horribly toxic, but straw board instead,” says Martin who is also a co-founder of Bristol community hub, Hamilton House, which is helping regenerate the inner-city.

Straw bales – low-impact and fuel efficient

Straw is an amazingly low-impact building material. Grown in fields with the power of the sun, straw absorbs carbon dioxide as it grows and needs very little processing to be compressed into straw board (for internal stud walls), or turned into straw bales for construction.

The actual construction is fast. The seven storm-proof houses were erected in only nine days, thanks to their prefabricated factory-made panels – straw bales sandwiched between timber frames – and precision-made to slot together perfectly.

Quickness of build adds to affordability as does fuel-efficiency. “Our homes help people out of fuel poverty; they are so well-insulated they need little heating even in the winter,” says Martin Connolly.

straw bales in factory

Modcell straw-bale design being pre-fabricated in factory.

Efficiency of straw bales backed up by science

The effectiveness of straw as a building material is now proven by Bath University. Working with ModCell, the university department of Architecture & Civil Engineering has demonstrated that straw building is durable, insurable, mortgageable and genuinely low impact.

Their durability were tested by being exposed on a Cornish coast, blasted by simulated hurricane-force winds, soaked in water to simulate flooding and exposed to roaring fires.

The academic team assessed energy consumption by monitoring ModCell homes at Lilac (Low Impact Living Affordable Community) in Leeds, finding savings of residential energy usage of up to 90%.

As well as being super-insulated and air-tight, the seven homes in Shirehampton, Bristol produce virtually all the energy they need to run. Rainwater harvesting cuts water and sewage bills, while LED lights, solar panels and an air-source heat pump all help reduce light and heating costs.

The homes crucially include Mechanical Ventilation Heat Recovery (MVHR) – the green ventilation system that cannily swaps heat from the house’s stale air with incoming fresh air, ensuring stable temperatures, better air quality and drastically reducing heating bills and carbon footprint. The combination of straw bale construction and MVHR means the homes stay warm in winter and cool in summer.

The two-bed two-storey and three-bed three-storey homes are priced between £220k and £235k. A bargain compared to Bristol house prices, Martin would like to increase the affordability of future straw bale developments. 

straw bale houses

Construction complete, the houses are being eco-fitted, on a very ordinary-looking building site.

Calling landowners and communities 

One of the reasons houses are so expensive is that developers sell houses at the highest price they can command.

As a green developer, Martin Connolly, has a radically different approach:

“Our aim is to support communities to create straw bale housing at affordable prices, similar to the Lilac housing co-operative,” he says. 

Connolly and Callaghan‘s and ModCell‘s next project planned for June will see 49 homes built in Shirehampton.

“It is ripe for community-led development. We are looking for ways to make this possible and welcome enquiries,” says Martin Connolly.

As well as looking for community developers, Martin Connolly is also looking for others sympathetic to his housing vision.

“We want to work with other partners including local authorities and landowners in a co-operative way to deliver genuinely affordable, low-impact housing.”