Retrofit – exterior solid wall insulation

One of the hardest things to do is to insulate period properties, especially those with solid walls. It’s even harder to do it cost effectively, and in many instances where insulation has been used internally, there have been subsequent problems with damp and interstitial condensation.

Before and after insulation of period propertyResearch at Oakridge Laboratories in California – the US equivalent of our Building Research Establishment (BRE) – except that it is state funded and entirely independent – has shown that insulation placed on the outside of a thermal mass (eg solid brick/masonry wall) will perform 8x better than if placed inside. You can read about the science here:


So by placing insulation (expanded polystyrene or phenolic foam boards) tightly sealed around the exterior of a solid wall building, thermal bridging and air leakage is reduced, thereby keeping the interior warm in winter and cool in summer.

With mechanical ventilation and heat recovery the internal living environment is further improved.

Side by side terraced house comparison

Even energy conscious owners of newer properties are investing in the benefits of retrofit external insulation.


Although external insulation performs better, where the exterior façade cannot be altered in Listed Buildings, careful installation of interior thermal plasterboard helps to considerably reduce heat loss through external walls.

specialists in
period and listed buildings, external wall insulation and energy saving ICF homes

all trades restoration new build alterations conversions