Electro-chemical machining

This report introduces the reader to the process and to the requirements which must be considered for its installation on the shop floor. Although only electro-chemical shaping is dealt with, many of the parameters investigated are fundamental to other configurations. The machining characteristics of several high strength alloys and die steels have been investigated; also of aluminium and mild steel. Electrolyte heating effects and the physical attributes of the machined surface have been considered. Electrode and workpiece shapes have been simulated for static field examinations and these followed by investigations under dynamic machining conditions

An analysis of errors in the Energy Performance certificate database

Energy Performance Certificates (EPCs) are the adopted method by which the UK government tracks the progress of its domestic energy efficiency policies. Over 15 million EPCs have been lodged, representing a valuable resource for research into the UK building stock. However, the EPC record has a reputation of containing multiple errors. In this work, we identify many such errors and quantify how common they are. We find that 27% of EPCs in the open EPC record display at least one flag to suggests it is incorrect and estimate the true error rate of the EPC record to be between 36 and 62%. Many of these errors are caused by EPC assessors disagreeing on building parameters such as floor type, wall type and built form. Additionally, flats and maisonettes appear to cause more issues than other property types. This may be due to difficulties in assessing their location in the building and the nature of the surrounding space. We also suggest potential new methods of quality assurance which rely on machine learning and which could allow such errors to be avoided in the future

Addressing the thermal performance gap: Possible performance control tools for the construction manager

Construction practice has failed to deliver buildings that consistently meet their expected thermal performance; however, examples of good practice do exist. Buildings can be designed and built within acceptable tolerances and meet nearly zero carbon standards. Unfortunately, due to the negative implications associated with the performance gap there have been attempts to divert attention from measurement, with some being critical of methods that were used to identify the variance in building performance. However, the tools have proven reliable and the practice of thermal measurement which was once limited to scientists is finding its place in industry. Measurement is becoming more accepted and different tools are being used to assess thermal performance. The tools can add value to inspections, building surveys and assist with quality control. Construction professionals, not least construction managers, are gaining valuable insights through research undertaken and observations gained. The tests reviewed provide new methods of capturing evidence on building performance, thus allowing valuable information on the quality of design, workmanship and process to be gained. Use of thermal measurement and analysis tools should result in further improvements to building performance. The data from major performance evaluation projects are reviewed and presente

Barriers to domestic retrofit quality: Are failures in retrofit standards a failure of retrofit standards?

Thermal retrofits of homes are central to the UK's fuel poverty and net zero carbon policies but there are concerns about poor quality installation and so new standards are to be introduced (PAS2035). We have explored retrofit installers' perceptions of the barriers to installing internal wall insulation (IWI) and of current regulations and standards for retrofits. We conducted four focus groups with retrofit installers. Thematic analysis identified three themes. (1) IWI is viewed as impractical in situations other than new builds, extensions and conversions as it is too time-consuming and expensive. (2) Installing IWI is perceived as an unskilled job with no need for training or referring to standards during installation. (3) Because standards lack credibility, installers can be sceptical of potential problems caused by on-site installation adaptations, for example thermal bridging. Our results show that retrofit standards have not improved retrofit quality. Awareness and credibility of standards is low, and new standards (PAS2035) will introduce additional costs which may reduce the pool of installers willing to engage in the retrofit market. Policies need to address installer training, professional identity and social practices, and reduce barriers to change in order to increase success. </jats:p

A Heat Loss Sensitivity Index to Inform Housing Retrofit Policy in the UK

A substantial number of dwellings in the UK have poor building fabric, leading to higher carbon emissions, fuel expenses, and the risk of cold homes. To tackle these challenges, domestic energy efficiency policies are being implemented. One effective approach is the use of energy models, which enable sensitivity analysis to provide valuable insights for policymakers. This study employed dynamic thermal simulation models for 32 housing archetypes representative of solid-walled homes in the UK to calculate the heat loss and the sensitivity coefficient per building fabric feature, after which a metric Heat Loss Sensitivity (HLS) index was established to guide the selection of retrofit features for each archetype. The building fabric features’ inputs were then adjusted to establish both lower and upper bounds, simulating low and high performance levels, to predict the how space heating energy demand varies. The analysis was extended by replicating the process with various scenarios considering climates, window-to-wall ratios, and overshadowing. The findings highlight the external wall as the primary consideration in retrofitting due to its high HLS index, even at high window-to-wall ratios. It was also established that dwelling type is important in retrofit decision-making, with floor and loft retrofits having a high HLS index in bungalows. Furthermore, the analysis underlines the necessity for Standard Assessment Procedure assessors to evaluate loft U-value and air permeability rates prior to implementing retrofit measures, given the significance of these factors in the lower and upper bounds analysis. Researchers globally can replicate the HLS index approach, facilitating the implementation of housing retrofit policies worldwide

IWI Thermal Properties and the Risk of Condensation and Mould GrowthImposed upon Neighbors at a Party Wall Junction

Internal wall insulation (IWI) is one of the few retrofit approaches to reduce heat loss through solid brick walls. Discontinuities in the insulation layer can result in thermal bridges, leading to reduced surface temperatures and the potential for condensation to form. Party wall junctions retrofitted with IWI act as discontinuities when neighbouring homes do not have IWI, leading to reduced surface temperatures on the neighbouring side. The condensation risk imposed on the uninsulated neighbour by a range of notional IWI systems are simulated, the resulting temperature factors indicate whether each system imposes a risk upon the uninsulated neighbour. Thicker, higher performing IWI systems were found to result in greater risk in the neighbouring property

Phase-locked mutants of Mycoplasma agalactiae: defining the molecular switch of high-frequency Vpma antigenic variation

Mycoplasma agalactiae, an important pathogen of small ruminants, exhibits antigenic diversity by switching the expression of multiple surface lipoproteins called Vpmas (Variable proteins of M. agalactiae). Although phase variation has been shown to play important roles in many host–pathogen interactions, the biological significance and the mechanism of Vpma oscillations remain largely unclear. Here, we demonstrate that all six Vpma proteins are expressed in the type strain PG2 and all undergo phase variation at an unusually high frequency. Furthermore, targeted gene disruption of the xer1 gene encoding a putative site-specific recombinase adjacent to the vpma locus was accomplished via homologous recombination using a replicon-based vector. Inactivation of xer1 abolished further Vpma switching and the ‘phase-locked’ mutants (PLMs) continued to steadily express only a single Vpma product. Complementation of the wild-type xer1 gene in PLMs restored Vpma phase variation thereby proving that Xer1 is essential for vpma inversions. The study is not only instrumental in enhancing our ability to understand the role of Vpmas in M. agalactiae infections but also provides useful molecular approaches to study potential disease factors in other ‘difficult-to-manipulate’ mycoplasmas

Retrofitting suspended timber ground-floors; comparing aggregated and disaggregated evaluation methods

It is estimated that around 80% of UK dwellings have uninsulated ground floors, representing a significant heat loss mechanism in these buildings. In this research, an aggregated assessment of dwelling heat loss was made using the electric coheating test before and after a ground floor retrofit took place. Heat loss was reduced by 24% (43 ± 18 W/K) indicating that suspended timber ground floor retrofits could improve thermal comfort for occupants and contribute to government domestic energy efficiency policy targets. The findings indicate that disaggregated evaluation methods, such as spot heat flux density measurements, may overestimate the benefits of fabric retrofits. Aggregate methods may therefore be more appropriate tools with which to evaluate retrofits. The U-value improvement resulting from the suspended timber ground floor insulation retrofit, derived via aggregate measurement, was 0.55 W/m²K. Disaggregated spot heat flux density measurements indicated the improvement was 0.89 W/m2K. This research also indicates that Energy Performance Certificates, are unlikely to provide a reliable estimate of energy savings, because they rely on default assumptions for fabric U-Values and ventilation rates. This has implications for policy evaluations as well as householders, who may be excluded from financial support for retrofits