Magdala Mews, Edinburgh

The two-storey garden dwelling of 10 Magdala Mews became a separate house when the adjoining townhouse was subdivided in the 1980s. The current owners knew that they wanted the later additions of a garage and conservatory demolished and replaced with a new extension, but it was a design challenge for this B-Listed home within the World Heritage Site.

The new room is expressed as a simple modern addition connected by a frameless glazed link which gives views through to the smaller enclosed garden. The main construction material is Thermoplan from NBT - a perforated fired clay block - with thermal performance such that it did not require additional insulation, even in this layout where over 70 per cent glazing to floor area ratio is achieved.

The rate of overall heat loss is further compensated by the use of triple glazing and a warm deck roof with sedum planting, the latter also helping the new building nestle into the leafy setting when viewed from the surrounding townhouses.