The design of a natural ventilation strategy requires the establishment of the location and size ... more The design of a natural ventilation strategy requires the establishment of the location and size of a series of purpose provided ventilation openings (PPOs). The success of the design is dependent on knowledge of the aerodynamic performance of the PPOs often described by their geometry (normally an area) and resistance to airflow. The incorrect interpretation of this information can lead inappropriate ventilation strategies and buildings that overheat and have an excessive energy demand. Many definitions of PPO area are used by standards, guidelines, text books, and software tools. Each can be assigned multiple terms and a single term can be assigned to different definitions. There is evidence that this leads to errors in practice. An effective area of a PPO, defined as the product of its discharge coefficient and its free area, is proposed as a standard description because it is unambiguous and its measurement is governed by recognised standards. It is hoped that PPO manufacturers will provide an effective area as standard and that its use will be recognised as best practice. It is intended that these steps will reduce design errors and lead to successful natural ventilation strategies and better buildings.
In this study a Building Information Model (BIM) tool is developed to simultaneously estimate emb... more In this study a Building Information Model (BIM) tool is developed to simultaneously estimate embodied and operational carbon over a 60 year life span for a typical four bedroom detached house. Using the tool, four different construction scenarios are evaluated, representing a range of current construction methods used in present day UK house building. The results show that cradle-to-gate embodied carbon represents 20–26% of the total 60 year carbon emissions, with operational carbon representing 74–80% of total emissions. Construction scenarios that reduce operational carbon by improving the thermal envelope led to a 1–13% increase in embodied carbon but a 4–5% decrease in operational carbon compared to the basecase construction method. Approaches to reduce embodied carbon in new-build housing are also studied and a 24% reduction is demonstrated through building fabric changes. The study recommends that a universally robust methodology for measuring embodied carbon will enable design decisions to be taken to reduce whole life carbon emissions through improved choice of materials. Due to material changes impacting on the thermal characteristics of a dwelling, and to an extent the structural characteristics, an integrated BIM tool will be essential in quickly establishing whole life carbon impacts during the design stage.
Distributed lag models (DLMs) to predict future internal temperatures have been developed using t... more Distributed lag models (DLMs) to predict future internal temperatures have been developed using the hourly weather data and the internal temperatures recorded in eleven spaces on two UK National Health Service (NHS) hospital sites. The ward spaces were in five buildings of very different type and age. In all the DLMs, the best prediction of internal temperature was obtained using three exogenous drivers, previous internal temperature, external temperature and solar radiation. DLMs were sensitive to the buildings' differences in orientation, thermal mass and shading and were validated by comparing the predictions with the internal temperatures recorded in the summer of 2012. The results were encouraging, with both modelled and recorded data showing good correlation. To understand the resilience of the spaces to heat waves, the DLMs were fed with weather data recorded during the hot summer of 2006. The Nightingale wards and traditional masonry wards showed remarkable resilience to the hot weather. In contrast, lightweight modular buildings were predicted to overheat dangerously. By recording internal temperatures for a short period, DLMs might be created that can forecast future temperatures in many other types of naturally ventilated or mixed-mode buildings as a means of assessing overheating risk.
In some areas of high air condition adoption there is potential for night purge natural ventilati... more In some areas of high air condition adoption there is potential for night purge natural ventilation to reduce the number of hours that the air condition system is operated, leading to a reduction in energy usage and associated carbon dioxide emissions. In this study we examine the potential efficacy of such a strategy implemented in an office building located in Pune, India. Using a dynamic thermal model we have demonstrated that around 10% annual cooling load saving can be achieved. Results from an actual application of this strategy in Pune demonstrate that when conditions are beneficial significant pre-cooling of the office space can be achieved before the occupied period, reducing the cooling load, saving energy, carbon emissions and costs.
SUMMARY For over 150 years the importance of good classroom ventilation has been acknowledged wit... more SUMMARY For over 150 years the importance of good classroom ventilation has been acknowledged with respect to providing a healthy environment that is conducive to learning, ensuring that school pupils are able to work optimally. Yet, despite guidance, many UK classrooms fail to meet adequate indoor air quality (IAQ) requirements. We have measured CO 2 and temperature in 28 classrooms disparately located around England for between 3 and 20 months. Excessively high CO 2 concentrations over 4000ppm are not uncommon in classrooms where the principle ventilation is via manually operated windows. IAQ tends to be better during the summer months when occupants are more likely to open vents for thermal comfort, compared to winter months. During November to December 2013, 85% of monitored manually ventilated classrooms fail to deliver average occupied CO 2 concentrations of less than 1500ppm.
This paper investigates the performance and control of natural ventilation during the heating sea... more This paper investigates the performance and control of natural ventilation during the heating season in order to avoid occupant discomfort. The current study examined different window configurations under a wide range of external temperatures and wind speeds using a CFD simulation tool. The results showed that thermally comfortable indoor conditions could be achieved in a UK classroom when external temperatures are as low as 8°C using high-level openable windows. At lower external temperatures, occupants are predicted to be thermally dissatisfied due to localised discomfort caused by draughts. The results from the CFD model also suggest that acceptable internal thermal conditions can be maintained with wind speeds up to 10m/s, for an external temperature of 10°C. The PMV results indicated that thermal comfort is achieved and is uniformly distributed within the classroom. This work will enable the UK's Education Funding Agency to have a greater understanding of the effective control of windows to eliminate wintertime discomfort and avoid unnecessary heating for naturally ventilated spaces.
CLIMA 2016 - proceedings of the 12th REHVA World Congress: volume 5, 2016
Natural ventilation solutions can provide sufficient outside air to maintain adequate indoor air ... more Natural ventilation solutions can provide sufficient outside air to maintain adequate indoor air quality (IAQ), which can improve occupants’ performance in classrooms and provide reductions in energy consumption for space conditioning. In this study, the effect of cool outside air and the vent opening configurations on IAQ and occupant thermal comfort in naturally ventilated classrooms during the heating season was examined. Dynamic and steady state computer simulations were performed to investigate the internal conditions of a naturally ventilated classroom, designed to meet the requirements of the Priority Schools Building Programme (PSBP) Output Specification. The modelled designs considered natural cross ventilation airflow through high-level top hung-out or bottom hung-in openings, and a stack (atrium). Dynamic thermal modelling results indicate that adequate IAQ and occupant thermal comfort could be achieved using natural ventilation. However, the CFD simulation results predicted occupant discomfort due to draughts in the regions close to the openings. Bottom hung-in vents reduced draught impact and the study also suggests moving occupants away from the draught zones to minimise the effect of discomfort draughts on occupant comfort. The air velocity and airflow patterns in the classrooms were influenced by the shape, size, location of internal openings, and the flowrate through the openings. This could be controlled by introduction of new openings with lower airflow rates through each opening.
The design of a natural ventilation strategy requires the establishment of the location and size ... more The design of a natural ventilation strategy requires the establishment of the location and size of a series of purpose provided ventilation openings (PPOs). The success of the design is dependent on knowledge of the aerodynamic performance of the PPOs often described by their geometry (normally an area) and resistance to airflow. The incorrect interpretation of this information can lead inappropriate ventilation strategies and buildings that overheat and have an excessive energy demand. Many definitions of PPO area are used by standards, guidelines, text books, and software tools. Each can be assigned multiple terms and a single term can be assigned to different definitions. There is evidence that this leads to errors in practice. An effective area of a PPO, defined as the product of its discharge coefficient and its free area, is proposed as a standard description because it is unambiguous and its measurement is governed by recognised standards. It is hoped that PPO manufacturers will provide an effective area as standard and that its use will be recognised as best practice. It is intended that these steps will reduce design errors and lead to successful natural ventilation strategies and better buildings.
In this study a Building Information Model (BIM) tool is developed to simultaneously estimate emb... more In this study a Building Information Model (BIM) tool is developed to simultaneously estimate embodied and operational carbon over a 60 year life span for a typical four bedroom detached house. Using the tool, four different construction scenarios are evaluated, representing a range of current construction methods used in present day UK house building. The results show that cradle-to-gate embodied carbon represents 20–26% of the total 60 year carbon emissions, with operational carbon representing 74–80% of total emissions. Construction scenarios that reduce operational carbon by improving the thermal envelope led to a 1–13% increase in embodied carbon but a 4–5% decrease in operational carbon compared to the basecase construction method. Approaches to reduce embodied carbon in new-build housing are also studied and a 24% reduction is demonstrated through building fabric changes. The study recommends that a universally robust methodology for measuring embodied carbon will enable design decisions to be taken to reduce whole life carbon emissions through improved choice of materials. Due to material changes impacting on the thermal characteristics of a dwelling, and to an extent the structural characteristics, an integrated BIM tool will be essential in quickly establishing whole life carbon impacts during the design stage.
Distributed lag models (DLMs) to predict future internal temperatures have been developed using t... more Distributed lag models (DLMs) to predict future internal temperatures have been developed using the hourly weather data and the internal temperatures recorded in eleven spaces on two UK National Health Service (NHS) hospital sites. The ward spaces were in five buildings of very different type and age. In all the DLMs, the best prediction of internal temperature was obtained using three exogenous drivers, previous internal temperature, external temperature and solar radiation. DLMs were sensitive to the buildings' differences in orientation, thermal mass and shading and were validated by comparing the predictions with the internal temperatures recorded in the summer of 2012. The results were encouraging, with both modelled and recorded data showing good correlation. To understand the resilience of the spaces to heat waves, the DLMs were fed with weather data recorded during the hot summer of 2006. The Nightingale wards and traditional masonry wards showed remarkable resilience to the hot weather. In contrast, lightweight modular buildings were predicted to overheat dangerously. By recording internal temperatures for a short period, DLMs might be created that can forecast future temperatures in many other types of naturally ventilated or mixed-mode buildings as a means of assessing overheating risk.
In some areas of high air condition adoption there is potential for night purge natural ventilati... more In some areas of high air condition adoption there is potential for night purge natural ventilation to reduce the number of hours that the air condition system is operated, leading to a reduction in energy usage and associated carbon dioxide emissions. In this study we examine the potential efficacy of such a strategy implemented in an office building located in Pune, India. Using a dynamic thermal model we have demonstrated that around 10% annual cooling load saving can be achieved. Results from an actual application of this strategy in Pune demonstrate that when conditions are beneficial significant pre-cooling of the office space can be achieved before the occupied period, reducing the cooling load, saving energy, carbon emissions and costs.
SUMMARY For over 150 years the importance of good classroom ventilation has been acknowledged wit... more SUMMARY For over 150 years the importance of good classroom ventilation has been acknowledged with respect to providing a healthy environment that is conducive to learning, ensuring that school pupils are able to work optimally. Yet, despite guidance, many UK classrooms fail to meet adequate indoor air quality (IAQ) requirements. We have measured CO 2 and temperature in 28 classrooms disparately located around England for between 3 and 20 months. Excessively high CO 2 concentrations over 4000ppm are not uncommon in classrooms where the principle ventilation is via manually operated windows. IAQ tends to be better during the summer months when occupants are more likely to open vents for thermal comfort, compared to winter months. During November to December 2013, 85% of monitored manually ventilated classrooms fail to deliver average occupied CO 2 concentrations of less than 1500ppm.
This paper investigates the performance and control of natural ventilation during the heating sea... more This paper investigates the performance and control of natural ventilation during the heating season in order to avoid occupant discomfort. The current study examined different window configurations under a wide range of external temperatures and wind speeds using a CFD simulation tool. The results showed that thermally comfortable indoor conditions could be achieved in a UK classroom when external temperatures are as low as 8°C using high-level openable windows. At lower external temperatures, occupants are predicted to be thermally dissatisfied due to localised discomfort caused by draughts. The results from the CFD model also suggest that acceptable internal thermal conditions can be maintained with wind speeds up to 10m/s, for an external temperature of 10°C. The PMV results indicated that thermal comfort is achieved and is uniformly distributed within the classroom. This work will enable the UK's Education Funding Agency to have a greater understanding of the effective control of windows to eliminate wintertime discomfort and avoid unnecessary heating for naturally ventilated spaces.
CLIMA 2016 - proceedings of the 12th REHVA World Congress: volume 5, 2016
Natural ventilation solutions can provide sufficient outside air to maintain adequate indoor air ... more Natural ventilation solutions can provide sufficient outside air to maintain adequate indoor air quality (IAQ), which can improve occupants’ performance in classrooms and provide reductions in energy consumption for space conditioning. In this study, the effect of cool outside air and the vent opening configurations on IAQ and occupant thermal comfort in naturally ventilated classrooms during the heating season was examined. Dynamic and steady state computer simulations were performed to investigate the internal conditions of a naturally ventilated classroom, designed to meet the requirements of the Priority Schools Building Programme (PSBP) Output Specification. The modelled designs considered natural cross ventilation airflow through high-level top hung-out or bottom hung-in openings, and a stack (atrium). Dynamic thermal modelling results indicate that adequate IAQ and occupant thermal comfort could be achieved using natural ventilation. However, the CFD simulation results predicted occupant discomfort due to draughts in the regions close to the openings. Bottom hung-in vents reduced draught impact and the study also suggests moving occupants away from the draught zones to minimise the effect of discomfort draughts on occupant comfort. The air velocity and airflow patterns in the classrooms were influenced by the shape, size, location of internal openings, and the flowrate through the openings. This could be controlled by introduction of new openings with lower airflow rates through each opening.
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Papers by Chris Iddon