Sahar Zahiri

The UK government has announced its Ten-point plan to annually install 600,000 low carbon heat pumps by 2028. Yet there is a lack of evidence showing potential overheating risk in dwellings retrofitted with heat pumps. This paper examines the prevalence and magnitude of summertime overheating across 24 naturally-ventilated social housing dwellings retrofitted with ground source heat pumps (GSHPs). The dwellings are located in a socially deprived area in Oxford (UK). The empirical study included longitudinal monitoring of indoor temperatures in the living rooms and bedrooms during the non-heating seasons of 2021 and 2022 (May-September), which included a record-breaking heat wave in July 2022. Indoor temperature and CO₂ levels were monitored across a subset of six dwellings in bedrooms alongside monitoring of window opening state in three bedrooms to understand the effect of natural ventilation in removing excess heat. About 136 thermal comfort surveys were conducted to ascertain the subjective responses of residents. Overheating risk assessment was carried out using CIBSE static and adaptive methods, which revealed that summertime overheating was prevalent across half the dwellings in the non-heating season of 2022, as compared to 17% overheated dwellings in 2021. Bungalows with upgraded cavity wall insulation and top floor flats facing south and south west had propensity to overheat. The variation in indoor temperature and CO₂ levels across a small sample also indicated the relationship between overheating and residents’ behaviour. Given that majority of the dwellings were occupied by retired elderly people with low income who are vulnerable to heat and cannot afford active forms of cooling, it is vital to deploy passive design measures such as appropriate shading devices suitable for a heating dominated climate and enhanced ventilation as part of home energy retrofits. Implementing reversible heat pumps coupled with solar PVs can provide cooling during heat waves, while delivering low carbon heat in the winter.

Deploying smart local energy engagement tools (SLEETs) in local energy projects enables users to better observe and control energy, and potentially become active participants in local energy management. Using a cross-project approach, this paper examines the prevalence, effectiveness and inclusiveness of 84 SLEETs deployed in 72 local energy projects in the UK from 2008 to 2018. An original framework for characterisation of SLEETs was employed, which grouped them into seven types and characterised in terms of level of interaction and interface design. Our study shows information-driven tools were most popular in community energy groups, while digital energy platforms - or interaction tools with numeric interface - were found popular in smart local energy sysem (SLES) initiatives. In contrast, interaction tools with visual interface, and tools offering control were found to be less popular. Spatial analysis revealed SLEETs were mostly deployed in areas with grid constraints (technology), active community energy groups (people) and engaged local authorities (policy). Effective SLEETs were found to stimulate engagement amongst people (social engagement), and between people and technology (operation and control), while inclusive SLEETs enabled inclusion of vulnerable and low incomes households. The acceptance and implementation of SLES initiatives can be enhanced by having effective and inclusive SLEETs that align with local users’ requirements and are supported by local stakeholders to foster trust. In future there is a need to develop appropriate metrics (key performance indicator) or scoring methods to measure their prevalence, effectiveness, and inclusiveness in a consistent manner.

Most studies on the link between indoor environments and productivity have been conducted in controlled, static conditions often unrepresentative of the real world. This paper uses a case-study-based, real-world approach to empirically investigate the link between indoor environment and workplace productivity in a mechanically-ventilated office environment in southern England. Evidence gathered during the baseline period was used to implement two interventions limiting peak temperature and CO2 concentrations. Environmental parameters (temperature, relative humidity, CO2) were monitored continuously. Transverse and longitudinal surveys recorded occupant perceptions of their working environment and self-reported productivity, while performance tasks provided proxy measures of worker performance in terms of cognitive ability, speed and accuracy. 

Workplace productivity was perceived to decrease when occupants perceived thermal discomfort and stuffy air. Correlations with perceived changes in productivity were stronger for perceived rather than measured environmental conditions and for perceived air quality rather than either measured RH or CO₂ concentration. This implies that occupants’ subjective feelings can impact their perceived productivity more than objective environmental conditions. Furthermore median task scores were 15% lower when conducted at CO₂ levels above 800ppm compared to below 800ppm. Insights from the study can help to optimise indoor office environments and improve workplace productivity.

This paper uses a case study-based approach to empirically investigate the relationship between indoor environment and workplace productivity in two contrasting office environments: one naturally-ventilated (NV), the other mechanically-ventilated (MV). Environmental parameters were continuously monitored over 19 months. Transverse and longitudinal surveys recorded occupants’ perception of their working environment and self-reported productivity, while performance tasks (numerical and proofreading) measured cognitive capability as proxy for measured productivity. Indoor temperatures and CO2 concentrations were found to be higher and more variable in the naturally-ventilated office. However, the correlation between occupant perception of their indoor environment and perceived productivity was stronger in the MV office. Occupants of the NV office were found to be more tolerant of their environment than their counterparts in the MV office. Task performance was affected by indoor environmental conditions such as indoor temperature and CO2 concentration. Interestingly in the NV office, the median scores were up to 12% higher for tests conducted at CO₂ concentrations

This study investigates an energy-inefficient council housing tower block in London, due for retrofit, by exploring the correlations between occupancy and energy consumption patterns, thermal comfort and building energy performance in the winter. The aim of this study is to evaluate the building performance and develop a reliable building simulation model to be employed in the second phase of the study for developing an energy-efficient and cost-effective retrofit strategy to support the council's plans. The research seeks to demonstrate the significance of using dominant occupancy and energy use profiles as opposed to relying on standardised profiles when calculating building energy consumption using building simulation software. The paper reports on the results from the first phase of the study where a quantitative methodology; including a questionnaire, structured interviews, indoor monitoring, and building simulation modelling was adopted. The results provide evidence that occupants’ socio-demographic characteristics have a considerable impact on household energy consumption and fuel bills. The results also show that indoor environmental issues experienced in many flats are partly attributed to the thermally inefficient building envelope and partly due to occupants’ patterns of operating their homes with evidence of excessive heating energy use in attempts to alleviate the indoor issues experienced.