|
Innovative methods of timber construction are common in Scandinavia, where there is an abundance of high quality timber. There are numerous timber prefabricated construction systems available that utilise Scandinavian and Baltic softwoods. Most are prefabricated structural panels that are sometimes left exposed for the interior finish using various methods of laminating and jointing between small lengths and sections of C16, C24 or TR26 rated softwood such as spruce and pine. The panels, generally, are complete wall pieces with windows and doors pre-cut, are mechanically manoeuvred and fixed together on site to form a structural shell with insulation, services and exterior cladding applied.
It was recognised that simple substitution with homegrown softwood was not an option. If a system was to be adopted generally it would need to stabilise the main structural components and eliminate the need for conventional trussed rafters. This would require a radical departure from existing practice.
A modular system based method of laminated portal frames with plywood panels on precast contrete brearers was suggested as a suitable model to follow
Early work performed by Coed Cymru and Cowley Timberwork looked at creating box sections from wide spruce planks formed into a hollow box using shoulder housing joints. Producing box beams is quicker and simpler than lamination. The resulting structure is light but very strong and easy to erect on the simplest foundations. Ty Unnos is a whole building solution including frame, envelope, finishes and fitting.
Infill Panels
The original system was conceived as a full system of infill components based on the sitka spruce box section as used in the structural components. These box sections would provide the infill for floor, walls and roof, simply stacking and spanning between the structural portals. The box section would then be filled with a locally sourced natural insulation such as hemp, sheep's wool or Warmcell insulation, thus creating a fully locally sourced component system which combines low-tech manufacturing with fast build times and insulative values approaching 0.15W/m2k
Prototyping has suggested that this approach can be made more efficient through the development of a larger panel system working on a 600mm component dimension.
Two systems being considered include a whole timber system that uses a small section spruce ladder beam with solid timber planking both internally and externally, and an OSB system which uses the same small section spruce ladder sandwiched between two layers of Scottish Oriented Strand Board. Both systems combine low-tech processes, drawing on the local manufacture of pallets, with high insulative values using locally sourced natural insulations.
Whilst OSB based components are simpler to manufacture, it is deemed as less sustainable due to the materials involved and the distance required to transport them and is therefore less appropriate to the principles of the Ty Unnos project. The use of a whole Sitka spruce infill panel also has the advantages of a greater flexibility in panel span, and can provide internal finishes if appropriate. Initial research suggests that both systems with a cavity dimension of between 200 and 250mm can achieve insulative values approaching 0.15W/m2k, when stuffed or injected with locally sourced natural insulations such as hemp, sheep's wool or Warmcell insulation.
Coed Cymru have also begun to develop additional components such as window and door cassettes. This will integrate a laminated small section hardwood window which is already in manufacture.
For further information please contact David Jenkins at Coed Cymru, 01686 650777
(OR see Staff Page for email addresses and officers' telephone numbers).
Coed Cymru, The Old Sawmill,
Tregynon, Newtown,
Powys SY16 3PL
Tel 01686 650 777
|
