Straw bale construction hits Haringey
Currently on site in Lordship Recreational Ground, Anne Thorne Architects’ Environment Centre is due to complete this summer.
Walking through Lordship Recreational Ground in Haringey on a sunny spring morning instantly put a spring in my step, at least as much of a spring as one can get when wearing steel toe-capped boots. I was on my way to see Anne Thorne Architects’ Environment Centre for Haringey Council, which started on site last month and is currently at the straw bale stage.
Approaching the site, I noticed a lot of regeneration occurring throughout the park, including new waterways, walkways and planting. Surrounded by residential properties and numerous schools, the park has the potential to become a ‘green’ heart for Haringey. The Environment Centre sits in the middle of Lordship Recreational Ground, which means that people will walk through the park to reach the building.
ATA partner and project architect Junko Suetake met me on site for the grand tour. The site was like no other construction site I had ever been on. For a start, it was predominantly female, with the all-female ATA and the support of straw bale construction specialists Straw Works, run by the very knowledgeable Barbara Jones. It was refreshing to see and a timely coincidence with AJ’s current Women in Architecture awards which aim to publicise female role models for aspiring architects and young women in practice. The site was calm, efficient and doubled up as a place of learning. Members of the community are working with Straw Works to learn the straw bale construction technique.
The initial concept was for the project to be constructed of natural materials, to sit lightly on the ground and not to interrupt the natural habitat of the park. The orientation of the building responds to the surrounding landscaping and topography. The building sits at the base of a slope and is raised off the ground to allow existing surface waterways and air to flow beneath the building. The orientation maximises passive solar gain, with a glazed south facade with inbuilt solar shading and natural ventilation to prevent summer overheating.
The project uses a renewable palette of materials, from low-impact timber foundations primary frame, to all natural insulation materials and non-toxic finishes such as clay plasters, rubber flooring, and natural paints. Anne Thorne Architects
The entire structure is timber apart from a small steel lintel which will sit above the large bi-fold door. The roof is constructed of engineered timber joists supplied by Cygnum and glulam beams. The roof is entirely supported by timber columns and the timber frame. The roof will be a sedum roof specified by Bauder, which aims to reflect the sloping hill of the site - a lifted section of roof breaks the length of the elevation, allowing light to flood in. The roof is perfectly orientated for PVs, as well as continuing the line of the hedgerow that is used by bats to navigate the lake at dusk.
Now onto the straw. Forget the fairy tales, straw bale construction can be strong, efficient and can simplify the construction process. From the very early stages of the design, Barbara Jones, Director of Straw Works, was involved in advising ATA. Barbara has been engaged in straw bale construction for 17 years and has published a book on the subject: Building with Straw Bales: A Practical Guide for the UK and Ireland.
According to Barbara, the UK generates approximately four million tons of surplus straw per year - which is enough for every house built, every year, to use straw bale construction. Also if a structure was in place, there is no reason why straw bale construction can’t be used for multi-storey (see AJ 24.11.11) and even high-rise buildings. Straw has a negative carbon footprint because it soaks up carbon from the atmosphere and locks it in. Straw could offer a solution to the carbon footprint of housing in the UK, replacing the high embodied energy of concrete and brick which are expensive in carbon terms both to make and to transport.
The straw for the Environment Centre was grown in Essex and purchased directly from a supplier who transports straw. It is ‘construction grade’ and is compacted by the supplier for transportation purposes. The construction process is fairly simple. A timber structure is erected, then the straw ‘building blocks’ are slotted into the frame, ensuring that they are compacted as tightly as possible. Hazel pins are used to support the straw internally and are hammered into place. Once the walls are complete, they will be rendered externally with traditional lime render and internally with natural clay render. The key to the success of a straw bale wall is that it is flexible and breathable. Barbara informs me that one bale of straw costs £3.50 including delivery to site. Not bad for an all singing, all dancing building block which eliminates the need for cavities, cavity trays, insulation and can achieve CSH level 5 without batting an eyelid. The down side to straw bale construction is that there is no British Standard and people are still nervous to use a product they have limited knowledge about.
Designed to Passivhaus standard, the Environment Centre will accommodate a community room, cafe, teaching room, small office and terrace when it completes this summer. Watch the ATA blog for construction updates and details about the opening of the building. This one will be worth a look.
The Environment Centre and the wider works in the park have been made possible through funding from the Heritage Lottery Fund, The Greater London Authority, The Environment Agency and the L B of Haringey.