The assumed U-values of solid walls represent a significant source of uncertainty when estimating the energy performance of dwellings. The typical U-value for UK solid walls used for stock-level energy demand estimates and energy certification is 2.1 Wm⁻² K⁻¹. A re-analysis (based on 40 brick solid walls and 18 stone walls) using a lumped thermal mass and inverse parameter estimation technique gives a mean value of 1.3 ± 0.4 Wm⁻² K⁻¹ for both solid wall types. Among the many implications for policy, this suggests that standard UK solid-wall U-values may be inappropriate for energy certification or for evaluating the investment economics of solid-wall insulation. For stock-level energy modelling, changing the assumed U-value for solid walls reduces the estimated mean annual space heating demand by 16%, and causes a proportion of the stock to change Energy Performance Certification (EPC) band. The analysis shows that the diversity of energy use in domestic buildings may be as much influenced by heterogeneity in the physical characteristics of individual building components as it is by variation in occupant behaviour. Policy assessment and guidance material needs to acknowledge and account for this variation in physical building characteristics through regular grounding in empirical field data.

There is a policy-driven focus, at present, on improving the energy performance of buildings. However, energy-related issues alone do not capture the full impact of buildings on occupants and the wider environment. The performance of a building also includes occupant wellbeing and indoor environmental quality. Specifically, in schools, indoor environmental quality (thermal comfort, indoor air quality, lighting and acoustics) is an important aspect. Additionally, the issue of the ‘performance gap’, generally focused on energy, also affects indoor environmental quality parameters and needs to be addressed holistically. This paper reports on a holistic building performance evaluation covering aspects of energy, thermal comfort, indoor air quality, lighting and acoustics. It assesses the performance issues and inter-relationships between energy and indoor environmental quality in a recently built school campus in London. Based on the evidence collated from this case study and supplementary literature, the endemic issues and constraints within the construction industry are explored, such as inappropriate design calculations and resistance to new low-carbon technologies. Further, lessons for improved performance in the design, operation and maintenance of schools are highlighted such as factoring in the changing building use trends during design and the significance of optimal operations and maintenance of building systems for better energy and indoor environmental quality performance. This study shows that if the building design focus primarily remains on energy, unintended consequence of indoor environmental quality underperformance may occur where there are conflicts between energy and indoor environmental quality objectives. An integrated approach to building performance can help address this issue. Practical application: There are often conflicts between energy efficiency and indoor environmental quality (IEQ) objectives in building design and operation. Most building performance evaluations are primarily focused on one set of these performance criteria. This building performance evaluation was done with an integrated energy and IEQ perspective. The study identifies the causes of underperformance in energy and IEQ in a recently built school in London. Some of the findings from this study provide lessons that are relevant across the industry for the delivery of low-carbon and healthy buildings. These lessons include methods to further strengthen the policy frameworks and design protocols along with overall improvements in the processes followed during design, construction and operation of schools and other non-domestic buildings. The paper can also inform building designers, contractors and facility managers about the ways to reduce the performance gap and achieve energy targets without unintended consequences for indoor environment.

Hospitals are controlled yet complex ecosystems which provide a therapeutic environment that promotes healing, wellbeing and work efficiency for patients and staff. As these buildings accommodate the sick and vulnerable, occupant wellbeing and good indoor environmental quality (IEQ) that deals with indoor air quality (IAQ), thermal comfort, lighting and acoustics are important objectives. As the specialist nature of hospital function demands highly controlled indoor environments, this makes them energy intensive buildings due to the complex and varying specifications for their functions and operations. This paper reports on a holistic building performance evaluation covering aspects of indoor air quality, thermal comfort, lighting, acoustics, and energy use. It assesses the performance issues and inter-relationships between IEQ and energy in a new building on a hospital campus in the city of Bristol, United Kingdom. The empirical evidence collated from this case study and the feedback received from the hospital staff help identify the endemic issues and constraints related to hospital buildings, such as the need for robust ventilation strategies in hospitals in urban areas that mitigate the effect of indoor and outdoor air pollution and ensuring the use of planned new low-carbon technologies. Whilst the existing guidelines for building design provide useful instructions for the protection of hospital buildings against ingress of particulate matter from outdoors, more advanced filtration strategies may be required to enact chemical reactions required to control the concentration levels of pollutants such as nitrogen dioxide and benzene. Further lessons for improved performance in operation and maintenance of hospitals are highlighted. These include ensuring that the increasingly available metering and monitoring data in new buildings, through building management systems, is used for efficient and optimal building operations for better IEQ and energy management. Overall, the study highlights the need for an integrated and holistic approach to building performance to ensure that healthy environments are provided while energy efficiency targets are met.

The indoor air quality (IAQ) of five low-energy London apartments has been assessed through the measurement of 16 key pollutants, using continuous and diffusive methods across heating and non-heating seasons. This case study approach aimed to assess the presence of pollutants within low-energy apartments and to better understand the role of ventilation and seasonal variations in indoor air quality. The results indicate strong seasonal variations, driven by increased natural ventilation rates over the summer monitoring period. A combined metric for indoor and outdoor pollutants ( I_tot) suggests that the IAQ in the winter ( I_tot = 17.7) is more than twice as bad as that seen in the summer ( I_tot = 8.6). Formaldehyde concentrations were lower in the non-heating season, indicating increased ventilation rates more than offset increased off-gassing, in contrast to findings in other studies. However, increased summertime ventilation rates were observed to increase the proportion of outdoor pollutants entering the internal environment. This resulted in higher indoor concentrations of NO₂ in the summer than the winter, despite significant reductions in outdoor concentrations. These results demonstrate the impact of ventilation practices upon IAQ, the influence of occupant actions and the complex relationship ventilation rates play in balancing indoor and outdoor sources of air pollution.