Summertime overheating in UK dwellings is seen as a risk to occupants' health and well-being. Dynamic thermal simulation programs are widely used to assess the overheating risk in new homes, but how accurate are the predictions? Results from two different dynamic thermal simulation programs used by four different experienced modellers are compared with measurements from a pair of traditional, semi-detached test houses. The synthetic occupancy in the test houses replicated curtain operation and the CIBSE TM59 internal heat gain profiles and internal door opening profiles. In one house, the windows were always closed and in the other they operated following the TM59 protocol. Sensors monitored the internal temperatures in five rooms and the local weather during a 21-day period in the summer of 2017. Model evaluation took place in two phases: blind and open. In the blind phase, modellers received information about the houses, the occupancy profiles and the weather conditions. In the open phase, modellers received the test house temperature measurements and, with the other modellers, adjusted their models to try and improve predictions. The data provided to modellers is openly available as supplementary information to this paper. In both phases, during warm weather, the models consistently predicted higher peak temperatures and larger diurnal swings than were measured. The models' predicted hours of overheating were compared with the measured hours using the CIBSE static threshold of 26℃ for bedrooms and the BSEN15251 Category II threshold for living rooms. The models developed in each phase were also used to predict the annual hours of overheating using the CIBSE TM59 procedure. The inter-model variation was quantified as the Simulation Resolution. For these houses, the blind phase models produced Simulation Resolution values of approximately 3% ± 3 percentage points for TM59 Criterion A and 1% ± 1 percentage point for TM59 Criterion B. The Simulation Resolution concept offers a valuable aid to modellers when assessing the compliance of dwellings with the TM59 overheating criteria. Further work to produce Simulation Resolution values for different dwelling archetypes and weather conditions is recommended. Practical application: Overheating in UK homes is a serious and growing risk to health and well-being. Dynamic thermal models are used to predict overheating risk in existing and proposed dwellings. Comparisons between predicted temperatures and temperatures measured in two test houses shed light on the accuracy of predictions for existing homes. CIBSE Technical Memorandum TM59 provides a strategy for predicting overheating risk in proposed dwellings. There are, however, differences between models' predictions. The concept of Simulation Resolution is introduced to quantify this inter-model variability. It provides modellers with a firm basis on which to determine whether TM59 overheating predictions are robust.

Purpose: Accurate values for infiltration rate are important to reliably estimate heat losses from buildings. Infiltration rate is rarely measured directly, and instead is usually estimated using algorithms or data from fan pressurisation tests. However, there is growing evidence that the commonly used methods for estimating infiltration rate are inaccurate in UK dwellings. Furthermore, most prior research was conducted during the winter season or relies on single measurements in each dwelling. Infiltration rates also affect the likelihood and severity of summertime overheating. The purpose of this work is to measure infiltration rates in summer, to compare this to different infiltration estimation methods, and to quantify the differences.Design/methodology/approach: Fifteen whole house tracer gas tests were undertaken in the same test house during spring and summer to measure the whole building infiltration rate. Eleven infiltration estimation methods were used to predict infiltration rate, and these were compared to the measured values. Most, but not all, infiltration estimation methods relied on data from fan pressurisation (blower door) tests. A further four tracer gas tests were also done with trickle vents open to allow for comment on indoor air quality, but not compared to infiltration estimation methods.Findings: The eleven estimation methods predicted infiltration rates between 64 and 208% higher than measured. The ASHRAE Enhanced derived infiltration rate (0.41 ach) was closest to the measured value of 0.25 ach, but still significantly different. The infiltration rate predicted by the “divide-by-20” rule of thumb, which is commonly used in the UK, was second furthest from the measured value at 0.73 ach. Indoor air quality is likely to be unsatisfactory in summer when windows are closed, even if trickle vents are open.Practical implications: The findings have implications for those using dynamic thermal modelling to predict summertime overheating who, in the absence of a directly measured value for infiltration rate (i.e. by tracer gas), currently commonly use infiltration estimation methods such as the “divide-by-20” rule. Therefore, infiltration may be overestimated resulting in overheating risk and indoor air quality being incorrectly predicted.Originality/value: Direct measurement of air infiltration rate is rare, especially multiple tests in a single home. Past measurements have invariably focused on the winter heating season. This work is original in that the tracer gas technique used to measure infiltration rate many times in a single dwelling during the summer. This work is also original in that it quantifies both the infiltration rate and its variability, and compares these to values produced by eleven infiltration estimation methods.

To assess risk factors for COVID-19 transmission and address the closure of mass gathering events since March 2020, the UK Government ran the Events Research Programme (ERP), following which it reopened live events in sports, music, and culture in July 2021. We report the rapid post-occupancy evaluation of Indoor Air Quality (IAQ) and associated long-range airborne transmission risk conducted in the Environmental Study of the ERP. Ten large venues around the UK were monitored with CO ₂ sensors at a high spatial and temporal resolution during 90 events. An IAQ Index based on CO ₂ concentration was developed, and all monitored spaces were classified in bands from A to G based on their average and maximum CO ₂ concentrations from all events. High resolution monitoring and the IAQ Index depicted the overall state of ventilation at live events, and allowed identification of issues with ventilation effectiveness and distribution, and of spaces with poor ventilation and the settings in which long-range airborne transmission risk may be increased. In numerous settings, CO ₂ concentrations were found to follow patterns relating to event management and specific occupancy of spaces around the venues. Good ventilation was observed in 90% of spaces monitored for given occupancies. Practical applications: High-resolution monitoring of indoor CO ₂ concentrations is necessary to detect the spatial variation of indoor air quality (IAQ) in large mass gathering event venues. The paper summarises COVID-19 ventilation guidance for buildings and defines a methodology for measurement and rapid assessment of IAQ during occupancy at live events that can be implemented by venue managers. Comparisons of the CO ₂ concentrations measured during the events identified the spaces at high risk of long-range transmission of airborne pathogens. Building operators should be mindful of the ventilation strategies used relative to the total occupancy in different spaces and the occupant’s activities.

Domestic energy use accounts for more than a quarter of total energy use in the United Kingdom (UK), with space and water heating accounting for almost 80% of this consumption. Energy efficiency is often the simplest and most cost-effective way of reducing energy use, and improving domestic energy efficiency can contribute significantly to reducing the UK’s greenhouse gas (GHG) emissions. A significant proportion of the UK’s energy stock remains inefficient, and over 80% of current housing stock will still be standing in 2050. Therefore, retrofitting existing buildings is fundamental to achieving energy efficiency improvements in the domestic sector. In order to reduce carbon emissions and improve domestic energy efficiency, the UK government launched the Green Deal in 2013 to improve the energy efficiency in buildings in the UK, reduce emissions from homes by 29%, and help meet carbon reduction targets. It aimed to overcome existing perceived barriers to the adoption of energy efficiency measures in the home and enable households and businesses to make energy-saving improvements to their properties, delivering a range of important benefits to the owner/occupier as a result. This paper critically assesses the impact of the Green Deal in shaping pro-environmental behaviours by drawing on two case studies. Lessons learnt from the UK’s Green Deal energy policy are presented, and implications for the UK government’s role in shaping energy policy and pro-environmental behaviours are considered.

Increasing extreme heat events in the tropics are creating dangerous environments in schools. There are limited data, however, on the extent of extreme heat in such classrooms and effective heat-mitigation strategies. This study presents the first long-term analysis of classroom temperatures in Ghanaian schools, measuring conditions in 16 classrooms in Accra over 389 days. It highlights the conditions experienced by schoolchildren and examines how roof type influences classroom temperatures. Children in metal-roofed classrooms were exposed to extremely high temperatures of up to 39.8°C, exceeding outdoor temperatures by up to 5.9°C, and being overheated for 72.5% of occupied hours, posing risks to children’s health and learning. Concrete-roofed classrooms were significantly cooler than those with metal roofs (by up to 5.8°C) and were on average 1.2°C cooler than the outdoor temperature, thus exposing children to fewer hours of uncomfortably hot temperatures. Adding a plywood ceiling under a metal roof halved overheating-hours, compared with a bare metal roof. These findings highlight the need for heat-resistant design principles when constructing or retrofitting schools to create safer, healthier classroom environments that are more conducive to supporting learning and the health of children in tropical climates. Policy relevance The findings of the first long-term monitoring of temperatures in 16 school classrooms in tropical Africa allow for evidence-based policymaking. This research highlights the urgent need to build and retrofit schools so they are heat-resistant to improve children’s learning ability and health. Using this new evidence of extreme heat in classrooms in Ghana, policymakers should revise the School Establishment and Inspection Policy and the Ghana Building Code to include climate-resilient design principles, prioritising heat-resistant roofing materials. This model can be replicated across tropical Africa to create heat-resistant schools and help address United Nations’ Sustainable Development Goal (SDG) 4 to ensure quality education in a changing climate.