Susan Roaf

Post-occupancy evaluation and field studies of thermal comfort

The similarities and differences are explored in both the aims and the methods between post-occupancy evaluations and field studies of thermal comfort in buildings. The interpretations of the field study results are explored, especially the ways the results differ from laboratory experiments. Particular attention is drawn to the dynamic nature of the interaction between buildings and their occupants. Answers to questions of the type used in post-occupancy evaluations are compared with results from field studies of thermal comfort, and the implications of these findings for the evaluation of buildings and the conduct of post-occupancy evaluation are explored. Field studies of thermal comfort have shown that the way in which occupants evaluate the indoor thermal environment is context-dependent and varies with time. In using occupants as part of the means of measuring buildings, post-occupancy evaluations should be understood as reflecting the changing nature of the relationship between people, the climate and buildings. Surveys are therefore measuring a moving target, and close comparisons based on such surveys need to take this in to account.

Pioneering new indoor temperature standards: the Pakistan project

Abstract Field surveys of thermal comfort have been conducted summer and winter in the five climatic regions of Pakistan to help the Pakistani Government to replace existing inappropriate indoor temperature standards. Results are presented which show large variations in desired indoor temperature with climate and season. The reasons for the differences are explored and an indication of the way in which responsive indoor temperature standards, which encourage the use of passive architecture and save energy in air-conditioned buildings, might be framed is presented.

Twentieth century standards for thermal comfort: Promoting high energy buildings

The urgent need to reduce anthropogenic greenhouse gas (GHG) emissions in a bid to meet increasingly stringent GHG targets has focused the attention of scientists on the built environment. The reason is that nearly 50% of all the energy in the developed world is consumed in buildings and it is here that the easiest savings can be made. Although the theoretical trend in building regulations is to favour lower carbon buildings, in reality new buildings have typically become more energy profligate year after year. Much of this results from increased mechanization, poorer building fabric and design, and the resource consumption patterns. Modern thermal comfort standards are partly responsible for increased levels of energy consumption in buildings as well as for encouraging unhealthier, less comfortable buildings because they drive the designers towards higher use of air-conditioning. A first step towards the radical overhauling of our approach to the artificial conditioning of buildings is to revise these standards. This article describes the evolution of the current standards and the problems inherent in the buildings they shape and serve and then proceeds to propose new methods of regulating thermal comfort in a warming world in which the cost of energy is rising.

Counting the costs of comfort

The recent Synthesis Report of the Intergovernmental Panel on Climate Change’s (IPCC) Fifth Report on Climate Change states clearly that the warming of the climate system is unequivocal and, since the 1950s, many of the observed changes are unprecedented over periods from decades to millennia (IPCC, 2014). It highlights that the atmosphere and oceans have warmed, the amounts of snow and ice have diminished, and the sea level has risen. It gives clear evidence of the often devastating impacts caused by anthropogenic climate change on the natural and human systems on all continents and across the oceans.

The wind towers of Bastakiya: assessing the role of the towers in the whole house ventilation system using dynamic thermal modelling

A thermal model of the complex wind environments in and around a traditional wind tower house in Bastakiya, Dubai, was constructed using Virtual Environment Software. The original house with its three wind towers was simulated and the potential to increase comfort in it using adaptive comfort criteria was explored with varying iterations of the wind tower design. The height of one tower was increased and reduced by 33%, and the cross-sectional area of a tower increased and reduced by 50%. This article presents the results of these simulations and the three key methodological conclusions reached. Firstly, that only by using the adaptive comfort model was it possible to understand how the buildings actually operated in terms of the comfort they provide for tradition populations in this historic building. Secondly, that the whole house behaves as a self-regulating thermal system in which the internal ventilation system operates around on modal shifts in each of the three towers from updraft to downdraft airflows. Thirdly that these modal shifts occur around thermal thresholds that are a direct result of the cross-sectional area and height of the towers and that by changing the dimensions of the towers these thresholds can be raised or lowered. Thus, the geometry of the towers themselves provides some control over the temperatures experienced in the home and its indoor comfort environment.

Innovative approaches to the natural ventilation of buildings: the imperative for change

The world is changing faster than many of us thought possible. In our introduction to ASR 53.1 on ‘Transforming Markets in the Built Environment: Adapting for Climate Change’ (Roaf et al., 2010), we opened that special issue by outlining the key drivers for change in the global markets, being fossil fuel use and its consequence: climate change. The increasingly extreme weather now experienced around the world is ironically associated with the need to use even more fossil fuel to keep people comfortable in the resulting extremes of heat and cold. Those fuel price rises have in turn dampened global demand and slowed economic development, providing a glimpse of the undulating future plateau of fuel price increases that no one can accurately predict. The USA, the engine of the 20th century economy, has perhaps suffered the worst from soaring and falling oil prices. Arizona was the first domino state in the USA to succumb to the impacts of the ‘overzealous activity in the housing boom’ and the selling of sub-prime mortgages that in effect triggered the advent of the global economic crisis in 2008 (Roaf et al. 2012). The result has been catastrophic. In the city of Phoenix in Maricopa county, Arizona, well above a quarter of a million homes stood empty at the 2010 census (myfoxphoenix.com). Outrage at the management of this ongoing crisis we hear echoing through cities around the world today in movements such as the ‘Occupy Wall Street’ and ‘Occupy the Banks’ movements. Rising energy and food prices were among the triggers for the unrest in the Arab Spring movement, and governments globally are increasingly challenged in attempting to achieve and maintain economic stability in their own countries. Countries with the most mineral resources are doing the best, and where a modicum of social equality exists in those countries, prospects seem good until, of course, the minerals begin to run out. The entrepreneurial genius of the computer industry has provided the technological platform from which have been built the communication and data revolutions that connected this generation, increasing opportunities for decentralized social networking, thus taking some powers

Rethinking thermal comfort

‘Thermal comfort’ is the term used to describe a satisfactory, stress-free thermal environment in buildings and, therefore, is a socially determined notion defined by norms and expectations. The idea of what is comfortable has certainly changed from one time, place and season to another (Chappells & Shove, 2005). For instance, it is estimated that the Houses of Parliament in London were found comfortable at 15°C by the original inhabitants (Schoenefeldt, 2016), who wore heavier clothing than is common today. Schoenefeldt (2016, p. 165) remarks that attendants reported difficulty getting MPs, who all sat in different areas, to agree on a set temperature. ‘There was scarcely a meeting of the house at which there are not some members who would like the temperature to be at 55°F (13°C), and others at 70°F or 72°F’ (21–22°C). Large variation exists in indoor thermal comfort according to different climates, times of year and culture. These responses and the actions and the lifestyles and beliefs they engendered ensured that the human race could survive in almost all the wide variety of conditions to be found across the planet. In ‘Temperature and adaptive comfort in heated, cooled and free-running dwellings’ (in this issue), Nicol finds that in their everyday life 90% of Japanese subjects are comfortable in their own homes with a temperature range between 18 and 28°C. A similar analysis among Pakistani office workers gives a range of 21–30°C (Nicol, Raja, Allaudin, & Jamy, 1999). At the extremes people can be comfortable in indoor temperatures as low as 10°C and as high as 35°C or more. Nonetheless, in any one given situation the comfort range will tend to be much narrower. The ability to find different temperatures acceptable depends on the access to opportunities to modify conditions such as the ability to change clothing or activity level which will enable individuals to be more comfortable (Cole, Robinson, Brown, & O’Shea, 2008). The most powerful of these intervention opportunities is the provision of controllable mechanical heating or cooling. This is a perk of living in the modern world that is dependent on there being a local supply of reliable and appropriate energy. However, the phenomenon of global warming has made mechanical solutions doubly problematic: not only does it make the weather conditions increasingly difficult to predict and therefore to deal with, but the very use of fossil fuels to generate the necessary energy is increasingly part of its cause in the first place. This seeming contradiction makes the understanding of the nature of the human interaction with the thermal environment increasingly important. This special issue addresses some of the ways in which scientific research is addressing the issue. The science of comfort developed in the 20th century around the needs of the heating, ventilation and air-conditioning (HVAC) industry. Engineers needed to feed target conditions into their HVAC sizing calculations to ensure a comfortable or neutral environment for a group of building occupants. Comfort was repositioned and redefined as a product sold by the HVAC industry (Fanger, 1970, preface). The HVAC industry therefore needed to define ‘comfort’ in terms of the physical variables that could be controlled using the HVAC system. In such calculations, it is assumed that a thermal balance is needed between the environment and an ‘average person’, and this thermal environment is assumed to be constant. The terminology used by comfort researchers is that of engineering and physics – temperature, humidity and air speed, clothing insulation and watts of metabolic heat/m. It therefore answers the needs of the engineering community in a way that allows them to size their plant. In doing so, it also dissuades them from addressing the shortcomings of the approach. The most common definition of a ‘comfort zone’ or range of environments which are experienced as comfortable is based on the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) seven-point scale of comfort (Table 1). The

The wicked problem of designing for comfort in a rapidly changing world

In December 1931, the front cover of ‘The Aerologist’, the journal of the US air-conditioning industry, showed clearly the Comfort Crossroads reached in America in the heady days before the Great Depression of the 1930s. The naturally ventilated Empire State Building, started in 1929, had just opened and construction there was on the threshold of new technology – air-conditioning – that would revolutionize American buildings over the coming century (Cooper 1998). The crossroad sign shows the old way, with building occupants poisoned by the foul air of the cities around them and debilitated by carbon dioxide generated by soaring populations in the megalopolis. The air quality in New York was obviously unacceptable then, and it was to be decades before the noxious factories abandoned the worker-rich city centres in the wake of the automobile driven suburban revolution. Air-conditioning, with its filters and fans did play a winning hand, with those who could afford it, against the New York Health Board who were then urging its citizens to open windows and use cleaner air from high levels in the city. Many New Yorkers were chronically poor later in the 1930s, as they were around the world in the decade of the worst global economic crash of the 20th century. It is not surprising that 80 years later, in the thrall of the worst economic crash for decades, the world is at a new crossroads facing a similar dilemma on how best to provide comfort in buildings in a significantly more complex world. The Seventh Windsor Conference 2012 on Thermal Comfort and Energy use in Buildings (www.nceub.org) was called The Changing Context of Comfort in an Unpredictable World and was held from 12 to 15 April at Cumberland Lodge in the grounds of Windsor Castle. There were six themed sessions on: The complexity of comfort; Schools and non-domestic buildings; Domestic buildings; Over-heating and climate change; Comfort in hot climates and Comfort models and outdoor comfort. There were six fascinating workshops too on: Ways forwards for comfort standards; How to design comfortable buildings; New ways of looking at comfort and productivity; Comfort and behaviours; the challenges of Modelling real building performance and occupant comfort and how to use Mixed Mode ventilation successfully in hot climates. All subjects which generated not a little heat and light themselves. The palpable sense of the importance of this whole event was set by the first after-dinner speaker, Professor Shin-Ichi Tanabe of Waseda University in Tokyo. He held the audience spell bound when describing the problems of energy availability and the provision of comfort in Japan following the impacts of the earthquake on the Fukushima nuclear generation plant in 2011. His paper has been developed and is included in this issue. It should be required reading for all building designers. It gives a flavour of what we all may experience in our own working lives in a more chaotic future. Two other key-note talks helped to put the deliberations of the conference in context. Andy Ford, then President of CIBSE outlined some of the problems for building professionals in the reality of today’s construction industry in trying to design for comfort while delivering value to building clients as money becomes tighter in the economically challenged global market place. It is all very easy saying that we need mixed-mode buildings that also have air-conditioning – but who is going to pay for them? The need for reality checking the theories has never been stronger. Professor Wouter van Marken Lichtenbelt of the Maastricht University Medical Centre in the Netherlands gave a fascinating keynote address on developments in Thermal Physiology and his paper in ASR 56.1 outlines some of the key issues that physiologists can help us with. We need to know the fundamental physiological thresholds around our behaviours, dictating when we shiver, sweat, suffer heat stroke or hypothermia and when we die of heat or cold. In between these physical limits, of course, lies the challenge of how to design comfortable buildings and keep occupants healthy and comfortable too. We have tried over the past years to steer readers of our Special ASR Issues on a journey that will help them join in our fairly complex discussions on ways forward for building design. ASR 54.1 in 2010 was called Transforming Markets in the Built Environment: Adapting to Climate Change and did include a paper outlining the background history to the development of the discipline of thermal comfort research. Other papers in the issue showed how vital the subject is to our ability to adapt to future climates. It also showed how challenging the issues of human perception, preference and behaviour are to design for and to influence. ASR 55.1 in 2011 on Innovative approaches to the natural ventilation of buildings: the imperative for change was also an important step on the road to ‘Open Windowton’ and ‘Health Way.’ The significance of the issues in that volume are shown by the fact that its introductory paper outlining the imperatives for natural ventilation is regularly in the top one or two cited papers in this journal.

Solar Power: Using Energy from the Sun in Buildings

Solar Energy is the easiest form of renewable energy to integrate into the fabric of a building, and in turn a city, and is capable of providing a significant amount of the necessary electricity, heat and hot water for the comfortable operation of a building over a year. Over the last decade there has been a huge growth in large-scale solar generation plants using a range of technologies including Solar Thermal Power Plants, Parabolic Dishes, Solar Dishes, Solar Trough Farms, Solar parks and Solar Power Towers (Schlaich, 1995; Markvart, 2000) in large arrays. Solar energy must inevitably become the most widely used form of renewable energy for buildings and cities over the next decades, even if it is not the most energy productive of the renewables. This is for many very good reasons: 1. Building integration: Renewable energy as a design feature Solar energy is the easiest form of renewable energy technology (RE) to integrated physically into a building. It can be a driver for building form, as with passive solar sun spaces and collectors, and as building material, forming a rain screen cladding to the external envelope of a building (Gadsden, 2001, p. 23; Yannas, 1994, pp. 12–13). Photovoltaic (PV) systems and passive solar elements in particular can be an attractive architectural feature for designers. In addition solar technologies do not have the same problems of reverberation when coupled with a building structure as do wind generators and neither do they produce smoke as a system by-product as do fossil fuel burners, making their wider use in cities unacceptable. Solar heat collectors may need a small amount of power for the pump, but they do not require large amounts of electricity to run as do ground coupled heat pumps, and PV solar needs no power input. Solar technologies are clean, quiet, and robust to operate and can result in avoided costs of construction if used as rain screen cladding. They may require occasional cleaning over time depending on the climate in which they are located.

The Oxford Solar House

This paper presents preliminary results from the first nine months of monitoring the Oxford Solar House (OSH) which was built, in particular, to evaluate the potential for photovoltaics to contribute cost effectively to domestic energy supply in the UK. The house was built in a south facing site with good solar access. It has a 4kW PV system integrated into the roof structure and a 5m2 solar thermal domestic hot water pre-heat. The house was designed to require a minimum of energy for heating, cooling and lighting, therefore optimizing the significance of the contribution of the solar electric supply. The performance of the PV system is presented, as well as an analysis of the whole design strategy to minimize energy loads.