Thermal mass meets with timber-frame construction
Sustainable design and operation will be combined in a new 3-storey office building for the British Geological Survey at Keyworth near Nottingham with a glulam timber frame structure and Tarmac TermoDeck to maximise natural heating and cooling.
Andreas Scharge, a senior engineer with engineering consultancy Ramboll Whitbybird, explains, ‘The project brief was to design a building with a clear focus on sustainability which could achieve a BREEAM “Excellent” rating. A timber frame was preferred over steel by the client at an early stage because the composite frame solution combines the low embodied energy and low CO2 figures with the thermal-mass advantaged of concrete.’
Using thermal mass to reduce heating and cooling was a key part of the building design. TermoDeck works by exploiting the high thermal mass of structural hollow-core concrete slabs to control internal temperatures and distribute warm or cooled fresh air through the building.
Andreas Scharfe continues, ‘In structures with high thermal mass, external daily temperature variations are not reproduced inside the building because maximum heat level reached during the day is delayed by the thermal mass of the building and can be counter-balanced by strategies that make use of the cool of the night. This “thermal lag” greatly reduces the need for further energy consumption. Because the two office wings are well insulated and the building has good heat recovery, TermoDeck replaces the need for energy-intensive and inefficient air-conditioning systems.’
To enable a TermoDeck scheme to be incorporated, the underside of the concrete floor soffit has been exposed. The TermoDeck precast planks are 260 mm deep and span 7.5 m across the timber frame which supports it. Crucially, each precast plank has received an in situ detail to positively link the frame and the planks.
The project demonstrates that sustainable elements such as TermoDeck can be used with timber as a structural building material to create a low-energy building.