Eco elegant engineering

Tuesday 12 Jul 2011

WAN's Caroline Stephens considers the aesthetic powers of gridshell structures at Glenn Howells' Savill Building

Glen Howells Architects’ gridshell visitors’ centre at Windsor is a fine example of sustainability, practicality and architectural elegance in one building.

The main feature of the building is its larch gridshell roof, which is clad with green oak. Both the larch and the oak are from The Crown Estate’s own sustainable sources from within the Windsor Estate. It was designed in conjunction with Buro Happold and Robert Haskins Waters Engineers along with The Green Oak Carpentry Company and Inwood Developments from Lewes, Sussex. (Buro Happold and The Green Oak Carpentry Company were also part of the Weald and Downland gridshell team).

Inwood Developments pioneered the use of long finger-jointed cladding and the use of glulam beams, and specialise in using native, sustainable materials and techniques for construction.

The gridshell roof, as a form of engineering a roof structure, allows large spans using (predominantly sustainable) timber. The Savill Building has a low curve - apparently the lowest a gridshell can go - so as not to interrupt the tree line and to benefit from solar gain. Its form in plan (90m long and up to 25m wide) seems to float over the ground like an elm leaf and rises to an elegant tip at each end.

The entire roof sits on an external steel ring beam which is supported by steel struts that provide secure roots into the ground. The visible lattice gridshell roof undulates over the space inside and ranges from 4.5m to 8.5m high oversailing the perimeter wall to provide solar shading.

The south facing wall is glazed floor to ceiling whilst the north facing elevation is predominantly solid (except for the top band of glazing) and behind a sloping green roof that rises up to the underside of the roof. The north elevation houses ancillary spaces and an art gallery (north light filters in through roof lights within the green roof), and the south elevation allows views into the park beyond from the shop and café.

The beauty of this building is its flexibility as an internal space due to the lack of internal structure. It can be configured internally to suit many different programmes and functions. Personally, I like this building because of its sinuous, elegant roof, constructed using locally coppiced timber, and how one can see its exposed veiny structure intersecting with the other materials of glass and steel. It is light and airy and a great space to experience.

A brief history of the timber gridshell in the UK:
- The Workshop, Hooke Park, by Richard Burton of ABK and Frei Otto, with the engineers Buro Happold, uses spruce thinnings from the forest that form a compression grid-shell structure. Complete in 1989.

- Downland Gridshell, Weald & Downland Museum, Sussex, England, 1996 - 2002ECA collaborated with structural engineers, Buro Happold, and the Green Oak Carpentry Company to develop this innovative, low energy structure. The gridshell was formed from a flat lattice of green oak that was lowered into a three-dimensional shape with the use of gravity.

- The Savill Building is a visitor centre at the entrance to The Savill Garden in Windsor Great Park, Surrey, designed by Glen Howells Architects, Buro Happold and Robert Haskins Waters Engineers.

- Flimwell Woodland Enterprise Centre Modular Gridshell in East Sussex was designed by Feilden Clegg and Atelier One with all sustainable materials sourced locally.

- Pishwanton Hand-Built Gridshell by David Tasker and Christopher Day was completed in 2002 on a modest budget. A craft centre for the Life Science Centre Trust, the undulating canopy is topped with a self-built gridshell spanning 10m.

Caroline Stephens

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