Dejan Mumovic

A review of the regulatory energy performance gap and its underlying causes in non-domestic buildings

This paper reviews the discrepancy between predicted and measured energy use in non-domestic buildings in a UK context with outlook to global studies. It explains differences between energy performance quantification and classifies this energy performance gap as a difference between compliance or performance modelling with measured energy use. Literary sources are reviewed in order to signify the magnitude between predicted and measured energy use, which is found to deviate by +34% with a standard deviation of 55% based on 62 buildings. It proceeds in describing the underlying causes for the performance gap, existent in all stages of the building life cycle, and identifies the dominant factors to be related to specification uncertainty in modelling, occupant behaviour and poor operational practices having an estimated effect of 20-60%, 10-80% and 15-80% on energy use respectively. Other factors that have a high impact are related to establishing the energy performance target, impact of early design decisions, heuristic uncertainty in modelling and occupant behaviour. Finally action measures and feedback processes in order to reduce the performance gap are discussed, indicating the need for energy in-use legislation, insight into design stage models, accessible energy data and expansion of research efforts towards building performance in-use in relation to predicted performance

A comparative study of benchmarking approaches for non-domestic buildings: Part 2 – Bottom-up approach

The bottom-up methods for energy benchmarking aim to derive a yardstick for energy performance based on a theoretical analysis of a building. While the top-down methods drive performance improvement by ranking a building against its peers, the bottom-up methods are focused on the building’s specific context. Consequently, the bottom-up methods can help identify how performance improvement could be materialised. These two complementary approaches can improve design practice and facilities’ management. Two bottom-up methods that could be used for energy benchmarking have been reviewed using UK schools as case studies: Building physics and aggregated end-use. The aim is to demonstrate how these methods could be used for benchmarking and identify their benefits and limitations. When all energy components are included in a model under expected operating conditions, the building physics method can be used to establish a baseline for energy performance. It is demonstrated that where this method is used under standardised operating conditions and is subject to minimum energy performance requirements, as prescribed by the Energy Performance of Buildings Directive (EPBD), it can be used to establish a benchmark for energy performance. It is also shown how aggregated end-use methods such as CIBSE TM22 can be used to define system level benchmarks, and identify the root causes for discrepancy between measured performance and design intent in a systematic way. 2014 The Gulf Organisation for Research and Development. Production and hosting by Elsevier B.V.

BIM Enabled Optimisation Framework for Environmentally Responsible and Structurally Efficient Design Systems

The present research investigates the potential for reducing the environmental impacts of structural systems through a more efficient use of materials. The main objective of this research is to explore and to develop a holistic and integrated methodology that utilises Building Information Modellings (BIM) capabilities combined with structural analysis and Life Cycle Assessment (LCA) as well as a two-staged structural optimisation solver that achieves efficient and environmentally responsible steel design solutions. The implemented workflow utilises Autodesk Revit-BIM, Tally-LCA and Autodesk Robot-Structural Analysis. RobOpt is the plug-in that has been established using the Application Programming Interface (API) of Robot and the .NET framework of C?, and it inherits several structural functionalities based on Robot Finite Element Method (FEM) engine. The proposed RobOpt application can be accessed via a graphic user interface (GUI) within the Robot software. The developed BIM-enabled optimisation methodology could be utilised as a design tool to inform early stage structural design solutions. A prototypical steel framed structural system under certain loads has been explored. The resulting bespoke I-beam sections from the custom genetic algorithm (GA) optimisation demonstrate that significant savings-up to 21%-can be achieved in all tested environmental indicators when compared to the standard UK catalogue of steel sections. Considering all, the proposed framework constitutes a useful and an intuitive workflow, which aims to quantify the environmental savings of structural systems by utilising, advanced computational analysis and common construction techniques.

Guidelines to Avoid Mould Growth in Buildings

Abstract There is now widespread acceptance that mould growth in buildings should be avoided as it may lead to adverse health effects. Consequently, it is critically important to have appropriate guidelines that address this issue. As well as reviewing the existing literature with regard to the state of the art of relevant mould-related research, this chapter reports on work aimed at developing mould-related Building Regulation guidance for dwellings in England and Wales. The major findings are, first, that although the factors that influence mould growth are well known, in buildings the variation and interrelationships of and between those are complex and, second, to deal with this complexity there is a fundamental choice between setting specific moisture performance criteria or using a ‘mould model’ to demonstrate compliance with regulations. At present, for England and Wales, the setting of moisture criteria is preferable and this chapter makes relevant suggestions for such criteria.

Energy Use Predictions with Machine Learning During Architectural Concept Design

Studies have shown that the actual energy consumption of buildings once built and in operation is often far greater than the energy consumption predictions made during design—leading to the term “performance gap.” An alternative to traditional, building physics based, prediction methods is an approach based on real-world data, where behavior is learned through observations. Display energy certificates are a source of observed building “behavior” in the United Kingdom, and machine learning, a subset of artificial intelligence, can predict global behavior in complex systems, such as buildings. In view of this, artificial neural networks, a machine learning technique, were trained to predict annual thermal (gas) and electrical energy use of building designs, based on a range of collected design and briefing parameters. As a demonstrative case, the research focused on school design in England. Mean absolute percentage errors of 22.9% and 22.5% for annual thermal and electrical energy use predictions, respectively, were achieved. This is an improvement of 9.1% for the prediction of annual thermal energy use and 24.5% for the prediction of annual electrical energy use when compared to sources evidencing the current performance gap.

Multilevel Computational Model for Cost and Carbon Optimisation of Reinforced Concrete Floor Systems

The cost and carbon efficiency of building structures could be enhanced by the current developments in design automation and optimisation techniques. New ways to systematically assess design alternatives based on cost and carbon parameters are necessary. The study proposes a multilevel optimisation approach that combines Building Information Modelling (BIM) data and Finite Element Modelling (FEM) with a constrained genetic algorithm. The optimisation methodology is tested in a prototypical building floor system. Structural grid configurations, floor thicknesses and columns sizes and reinforcement details are identified. The results showed that the cost optimum design is 3% cheaper than the carbon optimum design but it has 7% more carbon. In addition, the concrete in the floor is the biggest contributor in both total cost and carbon. Relationships between cost- and carbon-optimum designs for the tested structural configuration are also discussed.

Environmental and Behavioral Factors Affecting Residential Air Conditioning Use in Athens and London

The recent extremely hot summers in Europe have seen a rapidly expanding market in mechanical cooling in dwellings, especially in big cities. Along with urban climate factors, a number of behavioral factors are further contributing to a significant rise in cooling demand across the EU including countries with a more moderate climate, such as the UK. This chapter investigates environmental and behavioral factors affecting residential air conditioning use in two large EU cities with different climates – Athens and London. This scoping study analyses carbon and health implications of increasing cooling demand, and identifies important physical attributes and occupants’ behavioral patterns that affect air conditioning use, as well as, typical operational temperatures and schedules. The high satisfaction with domestic air conditioning units highlighted in both studies suggests that in the foreseeable future with changing climate the UK may experience a similar increase in market penetration of domestic air conditioning as has occurred in Greece over the last 20 years. This might have a major impact on the summer electricity load and domestic sector carbon emissions in the UK, which already accounts for almost 30% of the UK building stock emission.

Automatic ventilation control of trickle ventilators

Abstract The possible benefits of automatic ventilation control of trickle ventilators in dwellings are investigated. Such ventilators could offer an improvement in performance over fixed ventilators, due to their ability to adjust to environmental conditions without occupant interaction, thus improving energy efficiency and providing adequate indoor air quality. The theoretical performance of both pressure and humidity controlled ventilators are examined and simple equations are presented, calculating the opening area of a ventilator required to maintain a given air change rate as a function of pressure or moisture generation rate. Field tests in a highly instrumented test house were carried out on 3 types of trickle ventilator: fixed, pressure controlled and relative humidity controlled. A computer model of the performance of these types of trickle ventilators was developed, tested and then used to assess the performance of theoretical automatic ventilators, in terms of energy efficiency, moisture control and thermal comfort. The results of the simulations set out the potential for pressure ventilators to reduce the occurrence of over ventilation in dwellings, and for humidity controlled ventilators to reduce the incidence of excess humidity without significantly increasing ventilation heat loss.

The reduction in air infiltration due to window replacement in UK dwellings: Results of a field study and telephone survey

Abstract This paper reports the findings of a field study and telephone survey into the impact of window replacement on air infiltration and moisture problems in UK dwellings. The results of a telephone survey of 250 UK houses suggested that the installation of tight, well sealed replacement windows does not appear to be causing a significant increase in IAQ problems as perceived by the occupants. After having windows replaced only 2% of respondents (5 households) reported worse problems with condensation and only 1% (3 households) reported worse problems with mould. However, the results of “before and after” fan pressurisation tests on ten dwellings suggested that the installation of modern replacement windows reduced the predicted heating season mean background air change rate by an average 0.23 ac/h (standard deviation 0.08 ac/h). Analysis of the results suggests that installation of replacement windows in UK dwellings significantly reduces background infiltration rates, and that 65% of dwellings in the UK would have a predicted heating season mean air change rate below 0.5 ac/h after the installation of new windows. Houses with high moisture production, and low ventilation rates are potentially at risk from increased moisture problems after window replacement and may benefit from the installation of additional controllable ventilation during window replacement. However, the telephone survey which indicates that window replacement has not caused worsening IAQ suggests that occupants are ventilating adequately for their moisture production rates. If increased occupant venting occurs, then this may have the detrimental effect of increasing the space heating energy consumption.

Designing intelligent teaching and learning spaces: what do we know?

From an engineering design perspective, classrooms and lecture theatres are more complex than most structures environmentally. They usually have high heat loads, which are of a transient nature as pupils come and go, and from lighting which changes from class to class depending on the teaching methods used, and they generally have full or nearly full occupancy. Classrooms and lecture theatres also need to perform well acoustically, both for the spoken word and for music, and as sound amplification is generally not used, background noise control is critically important. All these factors, in addition to energy use, place constraints on building designers. Achieving the balance point between indoor environmental quality and energy use is unfortunately just one of many socio-technical engineering challenges in school buildings. Past attempts to reduce carbon emissions from existing school buildings and current ongoing efforts to deliver energy-efficient school buildings conducive to learning have had little success. Reasons for this include a poor understanding of (a) how to design, engineer, and facilitate learning spaces for changing pedagogical practices to support a mass education system, and greater student diversity, (b) how pupils and teachers use energy in school buildings, (c) how pupils and teachers interact with new technology, (d) how they respond to socio-technical energy conservation initiatives, and (e) how the overall indoor environment quality affects the learning performance of pupils and productivity of teachers. The absence of readily available energy use data matched with descriptors of physical form, indoor environment quality parameters, occupant use of space, and behaviour affects the accuracy of predicted energy consumption at the design stage and prevents the development of a transparent and validated strategy for modelling energy use in school buildings while providing indoor environment parameters required to provide a conducive learning environment. Another important perspective which is poorly understood is the process of developing an educational vision and translating this into material spaces focusing on the personnel involved, and the decisions made, carried forward, and abandoned at each stage. This special issue definitely indicates that our understanding of the design of learning environments is remarkably underdeveloped and that a step change in the approach to the design of school buildings is urgently needed. What is the way forward? School buildings are complex, dynamic, socio-technical systems seeking to provide solutions to a multitude of ill-defined and conflicting issues including the basic truth that the built environment is fundamental to the occupants’ sense of well-being and it is the totality of this idea that we need to understand and appreciate. To address the issue of total performance of school buildings at both ‘design’ and ‘in use’ stages, the problem, I believe, has to be viewed from a system perspective. Figure 1 shows the relationship among the building system (building structure and equipment installed), the environmental system (spatial boundaries, relationship between spaces, and indoor environmental parameters sensed by students and teachers), the activity system (use of controls, formal and informal learning activities, and flow of students within the school building), and finally the objective system (e.g. education of a certain number of children to a certain standard each academic year). This system perspective enables us to analyse how great the effect of