The U-value of an historic brick wall (c.840 mm) was higher than expected at 1.32 W/m2K.
Thermal insulation lowered the historic brick wall U-value by between 34 and 61%.
Insulation raised the surface wall temperature and lowered internal wall temperature.
Aerogel shows good potential for thermally insulating historic structures.
In-situ insulation underperformed by 13–25% compared to manufacturer's information.