As we aim to decarbonise the built environment, care must also be taken to minimise the negative impact of retrofit actions on historic buildings' fabric and cultural significance. Work to date in the UK has focused on the retrofit of historic solid masonry construction, with little research into historic timberframed buildings. With these buildings, where infill panels are beyond repair or have previously been substituted with inappropriate materials, there exists the potential to retrofit panels with a higher thermal performance. The research presented in this article compares the monitoring of three physical test panels mounted between climate-controlled chambers with digital hygrothermal simulations in order to investigate the risk of increased moisture which may threaten the surrounding historic fabric. Results of previously unpublished cyclical testing are is also included. Whilst all prediction methods successfully identified interstitial condensation where measured, major discrepancies existed between simulated and measured results, and between different simulation methods.
ABSTRACT:Caerphilly Castle (1268-70) is the first concentric castle in Britain and the second largest in the UK. The dramatic inclination of its ruinous south west tower has been noted since 1539. Comparing data from historical surveys and a terrestrial laser scan undertaken in 2015, this paper seeks to review evidence for the long-term stability of the tower. Digital documentation and archival research by architects is collated to provide data for structural analysis by engineers. A terrestrial laser scan was used to create a detailed three dimensional finite element model to enable structural analysis of the current shape of the tower made by tetrahedral elements. An automated strategy has been implemented for the transformation of the complex three dimensional point cloud into a three dimensional finite element model. Numerical analysis has been carried out aiming at understanding the main structural weaknesses of the tower in its present condition. Comparisons of four sets of data: 1539, 1830, 1870 and 2015 enabled us to determine change albeit between very different methods of measurement.
Purpose The energy retrofit of the existing building stock, and specifically the thermal upgrading of the buildings’ envelopes, has been identified as a key action for both the decarbonisation of the built environment and the reduction in fuel poverty. When considering the energy retrofit of heritage buildings it is, however, important to recognise both the technical issues that this entails and the potential impact on their cultural value and the emotional responses to it. The purpose of this paper is to focus on the thermal upgrading of historic timber-framed buildings in the UK. Design/methodology/approach The paper begins by exploring the cultural significance of this form of building construction, before examining three case studies using both quantitative and qualitative methodologies. Findings The results show that whilst the application of energy retrofit actions to this emblematic typology may have limited success, the emotional connection of the buildings’ occupants often results in the work resulting in higher user satisfaction than would otherwise be expected. Research limitations/implications Although limited in number, the three case studies provide an insight into the complex issues surrounding the low energy retrofit of historic timber-framed buildings. Further research into this area is encouraged. Practical implications The paper contains the monitoring of specific retrofit details, the results of which should inform future projects. Social implications The review of the cultural significance of historic timber-frame buildings in the UK underlines the importance of the conservation and continuing survival of these buildings. Originality/value Previous heritage retrofit research in the UK has focussed on solid wall construction with little investigation into the issues surrounding the retrofit of historic timber-frame buildings. This paper explores this previously under-researched area. Additionally, this paper begins to explore the possible links between occupants’ emotional connection to historic buildings and their perceived levels of comfort.
Energy retrofits have been identified as a key action to decarbonize the UK's building stock and improve hygrothermal comfort (DECC, 2014, OJEU, 2018). When undertaken with sufficient knowledge and consideration, the energy retrofit of historic buildings can be successfully achieved (Historic England, 2012). However, aesthetic, philosophical and technical issues must be fully understood in order to avoid unintended consequences (ibid.). As stated by the European Standard BS EN 16883 Conservation of Cultural Heritage-Guidelines for improving energy performance of historic buildings "[the] challenge is to reduce energy demand and greenhouse gas emissions without unacceptable effects on the heritage significance of the existing built environment" (British Standards Institution, 2017). To achieve this goal the Standard presents a systematic approach to facilitate the decision-making process (Figure 1). However, a key stage, mentioned in the Standard's text but not included in the original diagram, is the need for postoccupancy evaluation and feedback to close the loop. It is therefore essential for academic research to actively monitor and assess both current and future retrofit solutions for the historic built environment. Research in the UK in this field has so far focused on the predominant solid masonry construction (Baker and Rhee-Duverne, 2015, Currie et al., 2013, Gandhi et al., 2012), with little research covering the 68,000 historic timber-framed buildings that form an integral part of the UK and specifically England's cultural identity (Whitman, 2017). This paper explores this previously under-researched area. 1.1 UK Historic Timber-Framed Construction Archaeological evidence of timber construction can be found in the UK dating back to Neolithic times
Energy retrofits aim to improve the thermal performance of buildings’ external envelopes. With buildings of traditional construction there exists the risk that these improvements may lead to interstitial condensation and moisture accumulation. For historic timber-framed buildings, this potentially exposes the embedded historic timbers to conditions favouring fungal decay and insect infestation. Hygrothermal digital simulations can assess this risk, but these have limitations, especially regarding the study of historic and traditional materials, due to a lack of accurate material data. The research presented in this paper therefore uses the monitoring of physical test panels to examine the performance of four different infill solutions. These are, traditional wattle and daub, a composite of wood fibre and wood wool boards, expanded cork board, and hempcrete. The article focuses on the design and construction of the test cell and presents initial results from the first year of monitoring, following the initial drying phase. These showed no evidence of interstitial condensation in any of the panel build-ups, with increases in moisture content correlating directly with climatic measurements of wind-driven rain. Infill materials with low moisture permeability were seen to produce higher moisture contents at the interface with the external render due to the concentration of moisture at this point. Those panels finished in the more moisture permeable lime-hemp plaster, overall present lower moisture contents, with reduced drying times. The use of perimeter, non-moisture permeable, sealants would appear to potentially trap moisture at the junction between infill and historic timber-frame. The monitoring work is ongoing.
Energy retrofits aim to improve the thermal performance of buildings’ external envelopes. With buildings of traditional construction there exists the risk that these improvements may lead to interstitial condensation and moisture accumulation. For historic timber-framed buildings, this potentially exposes the embedded historic timbers to conditions favouring fungal decay and insect infestation. Hygrothermal digital simulations can assess this risk, however these have limitations, especially regarding the study of historic and traditional materials, due to a lack of accurate material data. The research presented in this paper therefore uses the monitoring of physical test panels to examine the performance of four different replacement infill details. These are, traditional wattle and daub, a composite of wood fibre and wood wool boards, expanded cork board, and hempcrete. The article focuses on the design and construction of the test cell and presents initial results from the first year of monitoring, following the initial drying phase. These showed no evidence of interstitial condensation in any of the panel build-ups, with increases in moisture content correlating directly with climatic measurements of wind-driven rain. Infill materials with low moisture permeability were seen to produce higher moisture contents at the interface with the external render due to the concentration of moisture at this point. Those panels finished in the more moisture permeable lime hemp plaster, overall present lower moisture contents, with reduced drying times. The use of perimeter, non-moisture permeable, sealants would appear to potentially trap moisture at the junction between infill and historic timber-frame. The monitoring work is ongoing.
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