Evaluating the influence of building fabric, services and occupant related factors on the actual performance of low energy social housing dwellings in UK

This paper empirically investigates the influence of building fabric, services and occupant related factors on actual energy use of six case study dwellings, located in three new low energy social housing developments in UK, covering a variety of built forms and construction systems (timber frame, hempcrete, steel-frame). Physical monitoring of indoor environment and window-opening is cross-related with building fabric and systems’ performance, and qualitative data gathered through occupant surveys, review of control interfaces and handover guidance, to understand the causes of the gap between modelled and measured energy use. Actual energy use is found to exceed design expectations by a factor of three, questioning the need for whole-house mechanical ventilation heat recovery (MVHR) systems at measured air permeability rates of 6m³/(h.m²) against the design target of 3m³/(h.m²). Lack of proper commissioning of MVHR and heating systems, combined with inadequate user comprehension about their operation and control leads to occupant ‘misuse’ wherein systems are de-activated, thereby negatively affecting indoor air quality. This is confounded by occupant factors related to higher demand temperatures, unexpected opening of windows during winters due to under-performance of MVHR combined with habitual behaviours, and over-use of heating systems to compensate for higher than expected air permeability

An empirical investigation of the link between indoor environment and workplace productivity in a UK office building

Most studies on indoor environments and productivity have been conducted in controlled, static conditions often not representative of the real world. This paper uses a case study-based, real-world approach to empirically investigate the relationship between the indoor environment and workplace productivity in a mechanically-ventilated office environment in southern England. Evidence gathered during a baseline period is used to implement an intervention (limiting peak temperature) with the aim of improving productivity. Environmental parameters (temperature, relative humidity and CO₂) were monitored continuously. Transverse and longitudinal surveys recorded occupant perceptions of their working environments, thermal comfort and self-reported productivity, while performance tasks objectively measured productivity. Although the building was operating within narrow temperature, RH and CO₂ bands, workplace productivity was perceived to decrease when occupants were thermally uncomfortable and when they perceived the air as stuffy. Correlations with perceived changes in productivity were stronger for the perceived environment than for the measured environmental conditions. In addition, median scores were 16% lower for tests conducted when CO₂ levels were in the 1000-1200ppm range compared to those conducted below 800ppm. Insights from the study can be used to optimise indoor office environments to improve staff productivity

Defining the link between indoor environment and workplace productivity in naturally and mechanically ventilated office environments

This paper uses a case study-based approach to empirically explore the relationship between indoor environment and workplace productivity in two naturally and mechanically ventilated office environments. Environmental parameters were continuously monitored over 19 months. Longitudinal surveys (online) recorded occupants’ perception of their working environment and self-reported productivity, while performance tasks (numerical tests, proof reading) measured cognitive capability. Indoor temperature and CO2 concentrations were found to be higher and more variable in the naturally ventilated (NV) office. Occupant perception of their indoor environment strongly correlated with their perceived productivity in both case studies. 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% lower for tests conducted at CO₂ levels >1400 ppm compared to those conducted below 1400 ppm, whereas in the MV office this threshold was 1000 ppm

Comparative evaluation of measured and perceived indoor environmental conditions in naturally and mechanically ventilated office environments

This paper uses a case study-based approach to comparatively evaluate the relationship between measured and perceived indoor environmental conditions in two office buildings, one naturally ventilated and one mechanically ventilated, located in south England. Environmental parameters (indoor and outdoor temperature and relative humidity, and indoor CO2 concentration) were continuously monitored at 5-minute intervals over a 19-month period (March 2017 to September 2018). During this time, occupant satisfaction surveys (both transverse and longitudinal) recorded occupant perceptions of their working environment, including thermal comfort, resulting in approximately 5700 survey responses from the two case studies combined. In the NV office, CO2 levels were high (often >2000ppm) and indoor temperature was both high (>27°C) and variable (up to 8°C change in a working day). In contrast, the MV office environment was found to operate within much narrower temperature, RH and CO2 bands. This was particularly evident in the little seasonal variation observed in the CO2 levels in the MV office (rarely above 1200 ppm); whereas in the NV office, CO2 concentrations exceeded 2000 ppm on 12% of working days during the heating seasons and less than 1% in the non-heating season. Despite these differences in measured indoor environmental conditions, occupants’ overall satisfaction with their environment was similar in both buildings. Occupants of the NV building were found to be more tolerant of higher indoor temperatures while neutral thermal sensation corresponded to a higher indoor temperature, indicating the role of adaptation. This has important implications for energy use in managing the indoor environment

Investigating the link between indoor environment and workplace productivity in an office environment

Most studies on indoor environment and productivity have been conducted in controlled, static conditions. This paper uses a real world case study to empirically explore the relationship between indoor environment and workplace productivity in a naturally-ventilated office environment. Environmental parameters (relative humidity (RH), CO2 concentration and air temperature) are continuously monitored during February 2017.Occupant perceptions of their working environment in winter (and summer) are recorded using the Building Use Studies (BUS) questionnaire. Analysis of the monitoring data shows that indoor RH is very low (2500 ppm). Air temperature is both high (>27 °C) and variable (up to 8 K change) indicating lack of window opening. Occupant feedback aligns with the measurements indicating low satisfaction with the indoor environment. Perceived productivity is found to strongly correlate with the perceived health and overall comfort. Insights from the study can be used to optimize indoor office environments to improve workplace productivity

Meta-study of the energy performance gap in UK low energy housing

This paper presents new evidence from a nationwide meta-study investigating the magnitude and extent of the difference between predicted and measured energy performance (energy performance gap) of over 50 low energy dwellings in the UK. Statistical testing of predicted and measured energy use is undertaken to assess the impact of occupancy related factors (number of occupants, occupancy type, pattern) on energy performance, and to predict the likelihood of the space heating energy performance gap in UK new build housing. The dataset was drawn from the UK Government’s National Building Performance Evaluation programme – which included the final reports, Standard Assessment Procedure (SAP) calculations and Domestic Energy Assessment and Reporting Methodology (DomEARM) results – and comprises 30 Passivhaus (PH) and 62 non-Passivhaus (NPH) dwellings, covering different built forms and construction systems. The majority of the sample comprised social housing dwellings built with masonry and timber frames and equipped with mechanical ventilation heat recovery systems. Although the average annual energy use (gas and electricity) in the PH and NPH dwellings was found to be 73kWh/m2 and 117 kWh/m2 respectively, electricity use was not significantly different between the two groups. All dwellings in the sample performed better than UK Building Regulations, however average energy use was higher than predicted by an average of 60%, but as much as 147% in PH and 241% in NPH dwellings. The overwhelming majority - 13 out of 14 PH and 35 out of 43 NPH dwellings - did not meet the predicted energy use, demonstrating a performance gap of 22 kWh/m2/year and 45 kWh/m2/year respectively. Occupancy was found to influence 45% of total energy use, with occupancy pattern being more critical than occupancy type and number of occupants. Despite the high levels of fabric thermal standards, space heating was found to be the largest energy end use (28% in PH and 42% in NPH dwellings) followed by domestic hot water (28%) and small appliances (21%), while the ratio of regulated to unregulated energy was found to be 70:30. The probability of an energy performance gap in space heating occurring in the population of new build housing was found to be over 80%. The study findings are important for bridging the gap between intent and actual performance of new low energy housing