Completed last year, New Cranes Court in Basildon, Essex is one of the largest zero carbon projects in the country and is also among the first affordable housing projects to attain Level 6 of the Code for Sustainable Homes (CSH).
Designed by architects The Tooley and Foster Partnership, the carbon neutral development for Swan Housing in partnership with Basildon Council is made up of 28 homes, comprising 16 family houses and 12 two-bedroom flats. Working with main contractor Denne Construction, Stewart Milne Timber Systems manufactured and supplied the build systems for all 28 units, which are made up of two- and three-storey housing and two, three-storey blocks of flats.
An early challenge for this project was that planners refused solar panels because of the proximity of the development to a listed church. To achieve CSH Level 6 without the use of a photovoltaic system, a highly efficient fabric solution to the building envelope was required.
"Making new homes as energy efficient as possible is the first step to reaching zero carbon, and one of the fastest and most cost-effective routes to achieve this is through a timber frame solution," said Alex Goodfellow, group managing director, Stewart Milne Timber Systems.
For this project the initial energy efficiency was achieved by specifying the company’s highly-insulated, precision-built, Sigma II Build System. This high-specification closed panel system makes the properties weathertight, with the airtightness of each unit designed to be below 3. The insulation offers high water resistance and long-term durability, prevents thermal bypasses within the panel cavities and, for this project, provided an external wall U-value of 0.15W/m2/K. Triple-glazed windows were used, with larger windows facing south, and mechanical ventilation with heat recovery (MVHR) systems were installed.
To accommodate the full MVHR systems, Stewart Milne Timber Systems used open-web joists for the floors of the houses in factory-made floor cassettes. As the MVHR ductwork didn’t need to go through the floors of the flats, timber I-beam cassettes were incorporated into the build system of the 12 flat units, which minimised build costs.
"To fully ensure that the primary airtightness was reached, tests were done at completion of the timber frame rather than at the end of the job, which confirmed the building performance and accuracy of build at every stage," said Mr Goodfellow.
