The SPAB (Society for the Protection of Ancient Buildings) Building Performance Survey looks at various aspects of building performance in older, traditionally constructed properties before and after energy efficiency refurbishment. The survey began in 2011 and measured, in seven houses: fabric heat loss, air leakage, indoor air quality, wall moisture behaviour, room comfort and fabric risk conditions.

In subsequent years, measurements were repeated in four of the properties that had undergone refurbishment and the findings published yearly as SPAB research reports. In 2014 the Building Performance Survey was extended in order to focus on the performance of moisture in insulated solid walls. Measurements of temperature and relative humidity (RH) through and either side of an insulated wall section have been made continuously in three properties since 2012 as Interstitial Hygrothermal Gradient Monitoring (IHGM). These provide an indication of moisture performance via the measurement of water vapour. The extended Building Performance Survey II expands on this monitoring to include measurements of moisture content (MC) within the wall materials at the same locations (material moisture monitoring).

Thus the Survey now looks at moisture within walls in two ways; measuring moisture as a vapour and moisture in its liquid state. It is hoped that these dual measurements will increase our understanding of moisture behaviour within these refurbished walls.

The properties in question are constructed of brick (Shrewsbury), granite (Drewsteignton, Devon) and cob (Riddlecombe, Devon).