Gwynne Anthony 2020

ART506 Dissertation 2019. Anthony Gwynne . 15 3.1.3 Measurement of breathability Considerations of breathability is the vapour permeable nature of a material, this quality can be expressed in its opposite form as vapour resistance. Vapour resistance may be measured in meganewton seconds per gram (MNs/g). An example of a material with an acceptable level of permeability is 19mm thick non-hydraulic lime render which has a vapour resistance of approximately 1.0 MNs/g. As a guide ‘breathable’ material that could be considered suitable for use in older buildings should have a vapour resistance of up to 2.5 MNs/g. However, water as a vapour is only one form of moisture threat to buildings and how materials perform in response to the possible presence of liquid water also needs to be considered (www.spab.org.uk ). 3.1.4 SPAB Building Performance Survey- performance of moisture in buildings Extensive research has been carried out by SPAB between 2011 and 2017 on various aspects of building performance in traditionally constructed buildings built before 1919 (www.spab.org.uk/interimreport/2011 ). In 2014, the survey was extended to include the monitoring of performance of moisture in the external walls of three separate buildings before and after refurbishment. The existing walls were fitted with sensor nodes on the internal and external wall surfaces, four sensors were located at varying depths throughout the walls and the interfaces of the applied insulation and wall. The sensors were used to measure and record the humidity and moisture movement within the walls (SPAB, 2014). This study was concluded in 2017 and the summary of findings relevant to this report is provided in Figure 1 (www.spab.org.uk/interimreport/2017 ).