Is conversion and refurbishment always the most sustainable approach?

Where a site has usable but redundant buildings it would seem obvious that the most sustainable way to develop them would be to make use of them as far as is possible and refurbish them to provide the accommodation required.  This approach potentially has huge advantages including:

  • Reducing the amount of new materials required in the build;
  • Reducing the amount of waste generated; and
  • Reducing the disturbance of the environment.

However, is that truly the most sustainable route to development?  Our clients faced exactly this dilemma when considering what to do with a number of unused farm buildings at Blacknest Farm.  The original plan was to convert five farm buildings, three of them to provide dwellings and two into flexible workspaces. Planning permission for this scheme together with the construction of a new dwelling was sought and had been granted.

As detailed plans and designs were developed the advantages of conversion were increasingly called into question.  However, rather than abandon the scheme the client opted to appoint Blewburton to investigate the sustainability case for conversion versus rebuild, to enable a decision to be made based on clear evidence.

Blewburton compared the two options against a range of sustainability criteria, selected to be consistent with standard sustainability assessment schemes.  In each case the two options were compared across the lifecycle of the buildings.

This proved an interesting investigation and the result showed that as long as material from the existing structures was salvaged and reused within the new build, as far as was possible, the new build option was the most sustainable over the lifetime. This was primarily because there are limitations on the improvements that can be achieved in the energy performance of refurbished buildings and they cannot match those achieved by well-designed new builds with good thermal properties.  Consequently, lifetime emissions of CO2 in the new build development were substantially lower than they would be for the conversion. In addition, building new dwellings enabled the design to meet the needs of modern living in a way that the conversion project was much less able to do – consequently the provision of good daylighting, thermal comfort and living space lent itself to better health and wellbeing for occupants.

Other issues that emerged were that although salvaging material from demolition activities can be time consuming, it is of great value in terms of reducing the new material required and in minimising waste arising.  These are important issues in the environmental impact of construction and often overlooked in brownfield site development.

This would not necessarily be the result in all cases but it demonstrates that it is worth taking a forensic look at the implications of conversion over demolition and new build on a site by site basis to determine which is the better and more sustainable option.

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