Prefabrication experiments - 196 - current practices - 07 - Prefabricated timber and straw bale panel construction

The return of prefab as an essential theme in construction relates to systemic low productivity, ecological imperatives and undoubtedly to changing demographics. Both work force and qualified labourers are becoming rarities in industrialized countries. Maintaining and increasing productivity in the context of rarefied labour commands inventiveness in matters of materials, methods and in the use of contemporary tools. Traditional construction trades are no longer the heart of the construction industry. Remarkably, however, as a demand for sustainable building strategies intensifies, vernacular construction methods are being reconsidered within a factory setting.  Rammed earth or even straw bale construction, although not habitually related to prefab are being produced in factory settings to reintroduce the benefits of using these natural construction techniques without their intensive labour constraints.

Blending contemporary tools and factory production with traditional construction techniques is the basis for a long-standing 1.8 million Euro research partnership between The Department of Architecture and Civil Engineering at the University of Bath and Modcell. Modcell is a company established about 200 km west of London whose main objective is to demonstrate the ecological potential of straw bale construction. The ongoing research has led to a series of experiments employing a low embodied energy factory produced and hybrid modular building panel with varying depths from 262 mm to 377 mm to 427mm. The prefabricated panels blend the structural capacity and precise nature of timber stud construction with the performance of thick compressed straw blocks inserted within the timber cavity. 

Prefabricated locally or in what is being termed as flying factories (varying contexts and temporary), the panels’ frames and straw bale infill are flat packed, transported, assembled and layered with a breathable battened sheathing, ready for any type of cladding or interior finishing to be installed on-site. The resulting wall issuper-insulated, and employs renewable, locally sourced, carbon sequestering, sustainable building materials: a perfectly sustainable and perfectible prefab solution. The standardized construction details for walls and roofs are designed for quick assembly and disassembly. The first experiment undertaken with the University of Bath was disassembled, reconstructed and adapted for a different site and use. The highly thermal resistant panels combined with weathertight detailing can meet the PassivHaus standard requiring little energy for heating or air-conditioning.

Modcell straw bale and timber panel - from the company website