Blog: Sustainability SECBE Awards 2020 finalist - Holy Trinity, Tulse Hill

17 June 2020

sponsored by Mulalley

Sustainability SECBE Awards 2020 finalist - Holy Trinity, Tulse Hill - straw bale build (submitted by Holy Trinity Church)

Tulse Hill Straw Build is a client-designed community building built by the community – over 500 volunteer builders to date constructing a large, permanent facility from straw and other up-cycled or low carbon materials in South London. The much-needed facility includes a large hall, kitchen, office, 3 group rooms, lift & link to Grade II Listed church. > Watch this Visualisation

Unlike commercial projects, which are completed quickly for economic reasons, a community self-build is deliberately slow. This enables maximum safe community engagement, innovative hands-on methods and continued fundraising during the build. The Church Trustees committed to rebuilding the long-demolished old hall in Autumn 2013. Foundation work started on 1^st April 2017. This year they will complete the 643m2 shell, and next year the internal works.

Everything about this build – the materials, method and finished facility – takes sustainability seriously in an innovative, ambitious project. It is the largest self-built urban straw-bale building in Europe and one of a handful of church buildings worldwide. In 2017 they were “hands-down winners” of the Green Church Green Futures Award.

Many low-energy buildings require high-energy produced materials. This build proves that self-build does not have to be limited to small-build and low-tech can be high-spec.

In more detail

The foundations are shallow, enabling hand-digging. Stone pillars are created from scrap tyres packed with pea shingle. These have been plate-tested to 1000kN/m2, 150% of load requirement. The base tyres are scrap tractor tyres, 1500mm diameter. Video here.  Avoidance of new concrete has saved c28 tonnes CO2.

The frame is English Douglas Fir, “stick built” hand-cut, hand-erected, and bolted together on site mostly by volunteers. The walls are straw. Video here. As a building material, when compressed in a wall, straw is extremely strong, highly fire-resistant, providing excellent acoustic and thermal insulation.

The internal shell is plastered with clay – a natural, breathable, low-impact plaster. Clay for the base coat came from their own excavations, processed by hand on-site - over 500m2, manufactured, applied by hand and air-dried. The external walls are rendered with lime. When lime sets it re-absorbs all the carbon dioxide that had been released during earlier processing.

By using timber, straw, clay and lime, the whole building can naturally adjust to movement in the London Clay, even with shallow foundations. In fact, Straw-bale buildings have been designed for earthquake zones for this reason.

Airtightness score will be 2.5 or better – four times better than building regs. The roof is recycled plastic Iko-Slate. Iko-slates have much higher impact resistance than natural slates, and therefore offer the more durable and sustainable option where falling debris from the higher church roof is an occasional hazard. Most of the south roof is inline PV panels, a 19.8kW array providing for the new hall, the church, and export.

Self-building by volunteers may not be the fastest or most efficient, but it is the greenest. Approximately 10% of the volunteers are positively inspired and practically trained for their own self-build projects. Through associations like the European Straw Bale Association, their films and conference presentations, experience and practice are considered inspirational across Europe.

Highlights:

• 479 tonnes CO2 saved instead of 400 tonnes CO2 emitted.
• Low-tech but high-spec:  643m2 Community Hall, hand-built, mainly by over 500 volunteers, aged 6-86.
• Use of straw, timber, clay and lime absorbs the inevitable movement of London Clay, allowing shallow, low-impact foundations, and giving a projected building lifespan of 100 -200 years.

About the Sustainability Award: 

High environmental and climate performance in construction aims to meet present day needs for housing, working environments and infrastructure without compromising the ability of future generations to meet their own needs in times to come. It seeks to limit impact on the natural environment and demonstrate whole life sustainability. It is most effective when organisational culture, high design quality, technical innovation and transferability are abundant.

> Find out more about the other finalists here