A comparison of calculated and subjective thermal comfort sensation in home and office environment

This study was conducted to investigate the accuracy of the PMV model in residential buildings in UK and to find out whether a true “context effect” exists in explaining discrepancies between predicted and observed thermal sensation of occupants. Sixteen participants were subjected to a thermal comfort study at both their homes and office. Each subject voted on their thermal sensation while air and mean radiant temperature, air velocity and relative humidity were recorded. The comparison of reported thermal sensation and those predicted using ISO 7730 showed that in general PMV under predicts the thermal sensation of occupants in both environments. The neutral temperatures found in homes and offices were respectively 3ºC and 2.5ºC lower than those predicted using ISO 7730. Together with 0.2ºC difference found between reported neutral temperatures at homes and offices, this suggests that there is a true context effect affecting occupants’ thermal sensation in different environments

Life-cycle assessment of a 100% solar fraction thermal supply to a European apartment building using water-based sensible heat storage

Providing 100% of a building’s heating and hot water using a solar thermal system in a European climate has been shown to be both practically feasible and functionally successful for a new apartment building in Switzerland. The research conducted a life cycle assessment of the solar thermal system and compared the results with an air-source heat-pump, ground-source heat pump, natural gas furnace, oil furnace and a wood-pellet furnace. Using a range of lifetime scenarios it was found that the solar thermal system displays potentially significant advantages over all other systems in terms of reductions for purchased primary energy (from 84 to 93%) and reductions in GHG emissions (from 59 to 97%). However, due to the heavy industrial processes and the particular metals used in manufacturing, the solar thermal system was shown to have a higher demand for resources which, in relation to the natural gas system, can be by a factor of almost 38. Potential impacts on ecosystem quality were marginally worse than for the heat-pump and fossil fuel systems due to resource use impacts whilst potential human health impacts were similar to the heat pump systems but better than the fossil and biomass fuelled systems

The nature of domestic electricity-loads and effects of time averaging on statistics and on-site generation calculations

This paper describes exploratory analyses of domestic electricity-profiles recorded at a high time resolution of 1 min on eight houses. It includes a detailed analysis of the effects of time averaging. For dwellings with on-site generation, such as micro-CHP, a better understanding of electricity profiles is important for the economic analysis of systems, and to examine the effects of widespread onsite generation on local electricity-networks. Most load data are available at half-hour intervals; averaging data over periods longer than a minute is shown to under-estimate the proportions of both export and import. The frequency distribution of loads is shown to be highly skewed, with varying distributions and an average load factor of 0.1. Further study is needed to develop more general relationships for a large sample of houses, to apply in design and research

Mechanical ventilation & cooling energy versus thermal comfort: A study of mixed mode office building performance in Abu Dhabi

In hot climates, office building ventilation and cooling dual operation can cause high energy consumption in order to maintain thermal comfort limits. Using mixed mode ventilation and cooling operation, incorporation of natural ventilation strategies can offer significant reductions in annual energy consumption. Natural ventilation operation can be used with an external air temperature ranging from 24 to 28oC. Within this paper, a literature on thermal comfort is completed to understand temperature limits for hot climates. This work details theoretical model analysis of a simple mixed mode office building located in a hot climate, Abu Dhabi, United Arab Emirates. This is completed using dynamic thermal simulation. The aim of this work is to evaluate the impacts on mechanical ventilation and cooling energy when raising internal comfort temperatures beyond 24oC; to a maximum of 28oC. Time/temperature analysis is completed for different months of the year to ascertain when thermal comfort temperatures are exceeded and full mechanical operation is required. Results from this analysis show yearly ventilation and cooling energy savings ranging between 21‐39% and demonstrate that higher mechanical cooling set point operations can be achieved when human occupants have access to openable windows

National survey of summertime temperatures and overheating risk in English homes

This paper presents one of the first national scale studies of summertime temperatures in English dwellings. Living room and bedroom temperatures were recorded in 207 homes across the England during the cool summer of 2007. Data was also collected by face-to-face household interviews. Fourteen homes (7%) were observed to be heated for part or all of the analysis period (July to August). Based on the BSEN15251 adaptive thermal comfort model, the 193 free-running dwellings would, in general, to be considered as uncomfortably cool. Over 72% of living rooms and bedrooms had more than 5% of hours below the BSEN15251 Cat II lower threshold, with over 50% having more than 5% of hours below the Cat III threshold. Detached homes and those built before 1919 were significantly cooler (p<0.05) than those of other type and age. Static criteria revealed that, despite the cool summer, 21% of the bedrooms had more than 5% of night time hours over 26ºC; which is a recommended upper limit for bedrooms. The bedrooms of modern homes, i.e. those built after 1990 or with cavity walls, were significantly warmer (p<0.05). The bedrooms in homes built prior to 1919 were significantly cooler (p<0.05). The living rooms of flats were significantly warmer than the living rooms in the other dwelling types (p<0.05).The incidence of warm bedrooms in modern homes, even during a cool summer, is of concern, especially as there is a strong trend towards even better insulation standards in new homes and the energy-efficient retrofitting of existing homes

Mechanical cooling energy reduction for commercial buildings in hot climates: effective use of external solar shading incorporating effects on daylight contribution

This paper investigates the effectiveness of multiple external shading devices and identifies the most effective fixed external shading configurations for commercial building types in hot climates. Daylight contribution is also analysed in detail in order to monitor the daylighting factor reduction including uniformity for each shading configuration. Existing dynamic thermal modeling software is used to completing analysis on a theoretical open office plan building. Simulation results indicate that multiple angled external shading is the most effective solution for commercial buildings in hot climates. The calculated diurnal cooling load reduction for East, South and West elevations are 46.20%, 41.16% and 46.53% respectively. Furthermore, daytime cooling load (kW) reduction is reduced by 17.80% using the optimum solution. All dynamic thermal simulations are compared against a base case to clearly show possible cooling energy reduction (MWh) and carbon dioxide emissions (CO2) associated with cooling system for single storey open office building

A simple model of domestic PV systems and their integration with building loads

Photovoltaic systems can reduce the CO2 emissions associated with the consumption of electricity in dwellings. One key issue that affects both the economic case for home installation and the integration with the mains electricity grid is the match between the instantaneous production and demand for power. This initial study considers a sample of 10 dwellings which were monitored under the UK Government’s Photovoltaic Domestic Field Trial. A simple PV system model is introduced and used to examine the variations in the balance between the imported and exported electricity of the monitored households. There are cases where a large proportion of the electricity generated by a PV system is be used directly by the household and instead is exported to the mains electricity grid. The possibility of using the model explore the effects of PV system size on the import and export balance, and the benefits of sharing production and consumption between nearby dwellings, is discussed

Occupant behaviour modelling in domestic buildings: the case of household electrical appliances

This paper presents a new approach to bottom-up stochastic occupant behaviour modelling for predicting the use of household electrical appliances in domestic buildings. Three metrics relating to appliance occupant behaviours are defined: the number of switch-on events per day, the switch-on times, and the duration of each appliance usage. The metrics were calculated for 1,076 appliances in 225 households from the UK Government’s Household Electricity Survey carried out in 2010-2011. The analysis shows that occupant behaviour varies substantially between households, across appliance types and over time. The new modelling approach improves on previous approaches by using a three step process where the three appliance occupant behaviour metrics are simulated respectively using stochastic processes to capture daily variations in appliance occupant behaviour. It uses probability and cumulative density functions based on individual households and appliances which are shown to have advantages for modelling the variations in appliance occupant behaviours

Measured internal temperatures in UK homes: a time series analysis and modelling approach

This paper presents an analysis of internal air temperatures measured hourly in the living rooms of 10 domestic buildings in the city of Leicester, UK. Time series analysis is used to develop empirical models of room temperatures in rooms that are neither mechanically heated nor cooled, during the summertime period of July and August 2009. The models are used in predicting future temperatures based on past measured values. Such models can enable overheating risk alerts for homeowners and public authorities to be more accurately estimated and targeted

Identifying trends in the use of domestic appliances from household electricity consumption measurements

Results are presented from a monitoring study of the electricity consumption of a sample of UK domestic buildings. Five-minutely average whole house power consumption was recorded for 72 dwellings at five sites over a 2-year monitoring period. The mean annual electricity consumption for the households increased significantly by 4.5% (t = 1.9; p < 0.05, one-tailed) from the first to the second year of monitoring. New techniques are developed which estimate the electricity consumption of different appliance groups, based on analysis of the five-minutely monitored data. The overall increase in electricity consumption is attributed to a 10.2% increase in the consumption of ‘standby’ appliances (such as televisions and consumer electronics) and a 4.7% increase in the consumption of ‘active’ appliance (such as lighting, kettles and electric showers). The consumption of different energy user groups (low, medium and high) is also investigated and low and high users are identified as contributing to the overall increase in consumption. The need for further investigation, such as quantitative and qualitative studies, to improve understanding in domestic electricity consumption is discussed