Gwynne Anthony 2020

ART506 Dissertation 2019. Anthony Gwynne . 17 -the foil facing of the insulation acts as barrier to moisture and restricts any movement and prevents evaporation to internal surfaces Riddlecombe 545mm thick cob faced externally with 100mm thick masonry and 20mm thick lime plaster internally Externally applied 60mm thick insulated lime render. Had the highest rates of relative and absolute humidity and moisture content, although is continues to dry excessive moisture Saturation margins widened and has an improved moisture profile and long-term trend of declining relative humidity Relative humidity is high and well above the threshold for mould growth 1 and is a risk to organic materials embedded within the wall such as joist ends, timber bearers and wall plates etc. Notes; Note 1: Relative humidity above 80% can cause mould growth which is prejudicial to human health and can cause serious health conditions such as lung disease. High levels of relative humidity is also a risk to organic materials embedded within the wall such as joist ends, timber bearers and wall plates etc. 3.1.5 Conclusion of SPAB findings The research carried out by SPAB (2017), summarised in Figure 1 has suggested there is evidence to support the long-held contention that the use of ‘breathable’ ‘vapour-open’) insulation minimises the risk of elevated moisture levels that can harm not only traditionally constructed (pre-1919) buildings but also their occupants health. A note of caution- It should be noted that SPAB research is at an early stage and further research may be required to confirm early findings. However, early research has found the thermal performance (U-value) of old, solid walls are frequently better than assumed under the current system of calculation. Indeed, SPAB findings to date are that standard U-value calculations (used across the construction industry to quantify the rate of heat transmittance through building elements) underestimated the thermal performance of the traditional solid walls sampled in 77% of cases. In some instances, heat loss was up to three times lower than calculated. Ultimately, this could have negative consequences for old buildings because the adoption of overly pessimistic theoretical U-values as the baseline for assessing the thermal performance of their walls may lead to disproportionate energy saving interventions that are not only unnecessary but also invasive and potentially harmful to historic fabric.