SOLAR OFFICE, DOXFORD INTERNATIONAL, SUNDERLAND
Architect: Studio E Architects
At the Marston Book Warehouse by Studio E Architects, the air leakage rate was better than bre's average benchmark, but the attached office building was less airtight and the Probe occupancy survey of the building highlighted the importance of improvement. Learning the lessons from this scheme, Studio E set out to significantly improve airtightness in its low-energy, photovoltaic office building at Doxford International near Sunderland.
The architect's strategy for improving airtightness included:
Ensuring that the client understood the implications and benefits of improving airtightness
Establishing a target leakage rate from the beginning and including it in the building specification
Letting the contractor know that the building would be tested against this standard
Paying attention to both the detailing and auditing of the drawings
Carrying out rigorous on-site inspections.
The airtightness requirement was built into the contract documents with a target air leakage rate of 10m3 per hour per m2 at 50 pascals. The architect had initially intended to set a target of 5m3 per hour per m2 at 50 pascals but the contractor was worried about achieving this. In the end, the pressure test showed that the completed building achieved 3.7m3 per hour per m2 at 50 pascals.
On this project, Studio E commissioned specialists to assist it; vetting drawings and carrying out site inspections with the architects. From this exercise, Studio E gained sufficient experience to feel confident that it understood, and could address the issues at hand. It now incorporates an airtightness strategy in most new projects.
'The cost of improving airtightness is not very great, much is already covered by good building practice,' said David Lloyd Jones, director of Studio E. At Doxford there were three main areas which needed special attention. The window and wall junctions, the roof structure of steel trusses with a profiled metal covering and the penetration of the floor slabs through the inner leaf of conventional external walls. The ends of hollow concrete planks also had to be sealed.
Lloyd Jones' experience emphasises the need for rigorous technical auditing of production drawings but since they do not necessarily cover every single junction of the building, on-site inspection and monitoring is vital.