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10 May 2022

Lessons From Conservation

Lessons From Conservation
Robin Dhar, Director of Donald Insall Associates


Arguably, the most environmentally sustainable building is the one you already have.

If, for example, we include the embedded carbon within old buildings that would be lost through demolition and add this to the carbon footprint associated with constructing new buildings in their place, we can make a sustainable case over the long term for the retention of existing buildings. Conservation and Sustainability have much in common.

Perhaps, then, we should only invest in new buildings when we really need to, using modern technology to effect highly efficient designs in terms of energy use, while thinking creatively and sensitively about the reuse and adaptation of existing buildings. While, though, many of these are not difficult to “retrofit” sustainably, listed buildings, especially those (2.5%) categorised Grade I or (5.8%) Grade 2* or 2 are another matter. Their character and special qualities can easily be undermined by insensitive, if well-intended, attempts to make them “sustainable”.

The solution lies in engaging specialists including conservation architects and in making thorough surveys of the fabric and history of each listed building. A client’s approach to sustainability needs to be discussed, too. What does the word “sustainable” mean to them, and what are their objectives for a particular building? An owner who plans to sell after a few years is likely to think differently from another thinking long term. Other specialists include sustainability consultant engineers and contractors used to working with historic buildings especially given that these behave differently from most modern buildings. Critically, they need to “breathe”. Attempts to make them airtight through new insulated layers of building fabric in the name of energy conservation can cause destructive damp, mould and rot.

The combination, however, of thick old walls, breathable high-performance insulation, secondary glazing, sensitive measures to manage damp, low energy fittings, and renewable energy can make a huge difference to the performance of a building with minimal impact, although all measures taken should be reversible if, in the future, it is thought best to restore a building to its original condition, as far as this is ever feasible.

The performance of single-glazed sash windows, often essential to the look of historic buildings, can be improved with the addition of draft seals between sashes and sash-boxes, while the installation of slim, bespoke secondary glazing within the thickness of sash beads provides significant improvements to thermal performance.

Insulation made from sheep’s wool, cork or wood fibre can also improve an old building’s thermal efficiency without high manufacturing carbon footprints. Cork, for example is waterproof, breathable, resistant to rot and naturally fire retardant, and is the renewable bark of a tree that absorbs CO2 while releasing oxygen.

As such measures imply, Conservation and Environmental Sustainability are compatible if we start with the aim of retaining what we can, thinking long term, designing adaptably for a loose fit and specifying, wherever possible, long lasting renewable materials. If we get these things right, future generations may yet thank us for bridging unnecessary gaps between these two reconcilable lines of thought. 

Donald Insall Associates have been working with The Grosvenor Estate including on a paper published June 2021, Heritage and Carbon: how historic buildings can help tackle the climate crisis, available for download here:   The practice has have also been working with Grosvenor on a pilot project to test different materials and approaches on an estate cottage, to inform future upgrading on the wider estate.