The new all-timber Woodland Trust headquarters has been showered with awards this year, and part of the credit for its success must go to its wood fibre insulation.
The £5.1m, 2,800m² building in Grantham was designed by architect Fielden Clegg Bradley and built by timber systems specialist B&K Structures. The core structure comprises 1,122m³ of cross-laminated timber (CLT) panels from KLH UK, and the same material was used in the lift shafts, stairs and balustrades. Externally, it is clad in Scottish larch.
The architect’s brief was to create an inspirational workplace for the Trust’s 200 staff, and also a flexible space that could be easily expanded to create a further 40 workstations. But it also had to be environmentally sound in construction, materials and use, with a minimal carbon footprint, low energy bills and the aim – which it achieved – of a BREEAM ‘Excellent’ rating.
Enter the Gutex wood fibre board insulation, supplied by its sole UK and Irish distributors, Carlisle and Athboy-based Ecological Building Systems (EBS).
Both Gutex Thermosafe Homogen and Multiplex Top water-resistant board were used to insulate the walls externally, with depths up to 282mm. In the roof, Thermosafe Homogen combines with Gutex’s Ultratherm product.
Thermal performance
EBS engineer Niall Crosson said the primary advantage of using Gutex externally was to increase the thermal performance of the construction, while putting a significant proportion of the insulation to the outside of the frame reduced non-repeating thermal bridges. The 282mm and 182mm walls achieve U-values, of 0.13W/m²K and 0.18W/m²K respectively, while the 240mm insulated roof achieves 0.15W/m²K. Insulating externally also moves the dew point to the outside of the wall optimising the structural durability of the building.
“Gutex wood fibre board is extremely vapour open, with a µ (mu) of only 3, yet it is still relatively dense as a material,” said Mr Crosson.
When insulating to the thicknesses specified for the building he added, the fact that Gutex produces boards to up to 240mm thick in a single ply decreases application time and reduces the risk of sheets delaminating.
“Gutex’s superior mechanical strength was another key reason for the specifier to choose these boards,” he said.
But undoubtedly the key attraction of the material for the building were its insulating performance, compatibility with the solid timber construction and contribution to the low environmental impact of the building.
