Domestic Energy Performance Certificates (EPCs) are used in the UK to provide energy efficiency ratings for use in policy and investment decisions on individual dwellings and at a stock level. There is evidence that the process of creating an EPC introduces measurement error such that repeat assessments of the same property give different ratings, compromising their reliability. This study presents a novel error analysis to estimate the size of this effect, using repeated EPC assessments of 1.6 million existing dwellings in England and Wales. A statistical model of how measurement error contributes to variation between repeated measurements is set out, and exploratory data analysis is used to decide how to apply this model to the available data. The results predict that the one standard deviation measurement error decreases with EPC rating, from around ± 8.0 EPC points on a rating of 35 to ±2.4 on a rating of 85. This predicted error is higher than the limit recommended in UK guidance except in very efficient buildings; it can also result in dwellings being rated in the wrong EPC band, for example it was estimated that 24% of band D homes are rated as band C.

Purpose: Compulsory airtightness testing was introduced for new dwellings in England and Wales in 2006 and in Scotland in 2010 to ensure that they are constructed according to design air permeability targets. These targets are set to limit heat loss through air infiltration. Previous work examining the large Air Tightness Testing and Measurement Association (ATTMA) data set of UK airtightness test data suggested that, in a proportion of dwellings, the targets were being met by post-completion sealing as opposed to airtight construction, but did not quantify the prevalence of this practice. The paper aims to discuss this issue. Design/methodology/approach: In this paper, the distribution of as-built airtightness and the proportion of dwellings undergoing post-completion sealing are estimated from the ATTMA data set covering 2015–2016. This is carried out by Bayesian statistical modelling, using the data set of recorded test results and a modelled representation of the testing process. Findings: This analysis finds the mode of the as-built distribution of air permeability as 4.38 ± 0.01 m³/m²h. It predicts that 39 per cent of dwellings aiming for one of the five most common design targets have sealing interventions at the point of pressure testing to meet their target. The as-built distribution of the ATTMA data is compared to airtightness test data obtained from just before compulsory testing was introduced, showing an improvement in the modal air permeability of 3.6 m³/m²h since testing became mandatory. Originality/value: This paper has investigated the available data beyond simply what is reported, to estimate what the real levels of airtightness in the UK new build stock may be.

As heat pump installation across Europe increases, monitoring system performance on a large scale is key for policy decisions and customer confidence. However, in-situ heat pump monitoring has been found in previous work to be very challenging. This paper explores current approaches to heat pump monitoring using two field-monitoring projects in Ireland and the UK where each investigated onboard and third-party monitoring systems. It was found that no approach was able to give accessible, accurate data at a low enough cost for widespread deployment of the monitoring. To overcome these challenges, a proposal is set out for a universal monitoring framework for domestic heat pumps, which would apply to every new heat pump sold in Europe. The framework sets out principles of producing monitored data which are standardised, accessible yet secure, accurate and low cost. Adoption of such a framework would improve customer confidence as well as allowing heat pumps to be compared with one another, driving improvements in heating system installation and lowering running costs. Comment is invited on the universal framework. POLICY RELEVANCE Monitoring the performance of domestic heat pumps at scale provides important information for policy decisions and householders and results in increased system performance. Large-scale monitoring has previously proven to be challenging. Using two research projects in Ireland and the UK, this paper highlights the lack of a cost-effective standardised monitoring approach and the resulting lack of data. A proposal is set out for a standardised approach to monitoring that would be embedded in all new domestic heat pumps sold on the European market at the manufacturing stage. Requirements are suggested for the data specification, storage, access and security, which would allow standard, accurate data to be extracted from any heat pump and compared with others. The additional cost of this is expected to be under €200 per heat pump.