Gwynne Anthony 2020

ART506 Dissertation 2019. Anthony Gwynne . 42 Element New works Works to existing buildings Maximum U-values 1 for new extension W/m 2 . K Maximum U-values 1 for conversions, renovations and material chance of use. W/m 2 . K Cavity walls (exposed and semi exposed) Solid walls 0.21 -- 0.55 0.3 Floors 0.18 0.25 Roofs 0.15 0.18 Windows 1.6 1.6 Doors 1.6 1.6 Notes: 1. The U-value is a sum of the thermal resistances of the layers that make up an entire building element- see 4.3 for a full explanation of what is a U-value. Figure 14: Summary of maximum current U-values for new works (extensions) and works to existing buildings in Approved Document LB1- tables 1, 2 and 3 (Source: www.gov.wales/buildingregulations-approved-documents) . Comparison of insulation thickness to meet current U-values in Figures 15 and 16 indicates non-vapour permeable insulations such as Kingspan which is much thinner in section than vapour permeable insulations such as cork and lamb’s wool which have less thermal resistance and are thicker. Thinner insulations take up less usable floor area when thermally upgrading traditional/historic buildings which typically have smaller rooms. This leads to the inappropriate use of non-vapour permeable insulations on solid vapour permeable walls with the consequence of trapping moisture and associated problems indicated in Figure 5. This is contrary to SPAB’s findings (paragraph 3.1.5) that concludes ‘excessive thicknesses of insulation and non-breathable materials should be avoided . 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 and people’s health’. SPAB suggest thinner vapour permeable insulations that are less high performing can achieve successful upgrades. The Welsh Governments net zero carbon emissions target by 2050 for new and existing buildings (paragraph 3.4.0) can only make this situation worse.