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Dt School of Architecture
This paper brings together objective and subjective data on indoor temperature and thermal comfort to examine the magnitude and perception of summertime overheating in two London-based care homes occupying modern and older buildings. Continuous monitoring of indoor and outdoor temperature, relative humidity and CO2 levels was conducted in summer 2019 along with thermal comfort surveys and semi-structured interviews with older residents and staff of the care settings. Indoor temperatures were found to be high (>30 °C) with bedroom temperatures often higher at night than daytime across both care settings. Limited opening due to window restrictors constrained night-time ventilation. Overheating was prevalent with four out of the five monitored bedrooms failing all four overheating metrics investigated. While 35-42% of staff responses perceived indoor temperatures to be uncomfortably hot, only 13-19% of resident responses were found to do so, indicating that elderly residents tend to be relatively insensitive to heat, leaving them open to overheating without realising it. Residents and staff in the modern care setting were less satisfied with their thermal conditions. As hybrid buildings, care settings need to keep both residents and staff comfortable and healthy during hot weather through night-time ventilation, management of heating and supportive institutional practices.
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.
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 empirically evaluates the extent of energy resilience achieved in a socially-deprived community in Oxford, through deployment of solar photovoltaic (PV) systems and smart batteries (internet enabled and controllable) across a cluster of 82 dwellings (households). The methodological approach comprised dwelling and household surveys, along with high frequency monitoring of household electricity consumption, solar PV generation, battery charge and discharge data. In the monitored households, average daily electricity consumption was found to be positively related with dwelling size, number of occupants and number of appliances used. Although 117MWh of PV electricity was generated within a year across 74 dwellings, peak generation did not match peak consumption, demonstrating the need for battery storage. Home batteries were found to increase self-consumption of PV electricity and offset grid demand through discharge of stored PV electricity marginally at an average of 6%, depending on the size of the PV system, surplus PV electricity available and size of the battery. Aggregating solar generation and storage at a community level showed that peak grid electricity demand between 17:00 and 19:00 was reduced by 8% through the use of smart batteries across 74 dwellings. In future, a local energy sharing scheme could be developed, wherein not all dwellings would need to have solar PV systems, but rather have internet enabled batteries that could be monitored and controlled virtually.
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 <1400 ppm, compared to those conducted above 1400 ppm, whereas in the MV office this threshold was only 1000 ppm.
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 (NV) and one mechanically ventilated (MV) located in southeast England. Environmental parameters (indoor and outdoor relative humidity (RH), CO2 and indoor and outdoor temperature) were continuously monitored at 5 minute intervals over a period of 19 months (March 2017 to September 2018). During the monitoring period, occupant satisfaction surveys (snapshot and longitudinal) were conducted to record occupant perceptions of their working environment, including thermal comfort, resulting in approximately 2600 survey responses from each case study.
In the NV office, CO2 levels were high (>2000ppm) and indoor temperature was both high (>27°C) and variable (up to 8°C change). The MV office environment was found to operate within much narrower indoor temperature, RH and CO₂ bands. This was evident in the little seasonal variation observed in the indoor CO2 levels in the MV office; whereas in the NV office, CO2 concentrations were over 1400 ppm for 20% of the working hours during the heating seasons and decreasing to 3% in the non-heating seasons, when windows were frequently opened. Occupants were found to have different levels of tolerance to measured indoor temperatures - neutral thermal sensation votes corresponded to a higher indoor temperature in the NV building, indicating the role of adaptation. Insights from the study can help in improving indoor environments of NV and MV offices.
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.
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.
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.