J. Fergus Nicol

The validity of ISO-PMV for predicting comfort votes in every-day thermal environments

Abstract One of the uses of ISO 7730 (predicted mean vote, PMV) is to predict the thermal sensations of people in buildings. This application is examined, using the ASHRAE database of field-studies. Taking these world-wide data as a single distribution, PMV is free from serious bias. There exist, however, underlying biases in relation to all contributing variables, and a further bias related to the outdoor temperature. These biases often combine to produce a substantial bias in PMV. In surveys of individual buildings, PMV often differs markedly and systematically from the actual mean vote, both for naturally ventilated (NV) and for air-conditioned (AC) spaces. Possible origins of the biases are discussed, and it is shown that it would be possible to modify PMV substantially to reduce them. Environmental consequences of the use of PMV are discussed. It is concluded that ISO 7730 in its present form can be seriously misleading when used to estimate thermal comfort conditions in buildings.

DEVELOPING AN ADAPTIVE CONTROL ALGORITHM FOR EUROPE

Abstract An adaptive control algorithm (ACA) has been developed as an alternative to fixed temperature setpoint controls within buildings. This paper describes both the theory behind the ACA and the findings from an EU-funded research project, smart controls and thermal comfort (SCATs), from which the form of the ACA was developed. The ACA was also tested in two air-conditioned buildings as part of the SCATs project and the results are presented. The results show that use of the ACA has potential for energy savings in the climate-control services of a building with no reduction in the perceived thermal comfort levels of that building’s occupants. Further refinement and testing of the ACA is required before it can be marketed.

Thermal comfort: use of controls in naturally ventilated buildings

Abstract A field study of the thermal comfort of workers in natural ventilated office buildings in Oxford and Aberdeen, UK, was carried out which included information about use of building controls. The data were analysed to explore that what effect the outdoor temperature has on the indoor temperature and how this is affected by occupants’ use of environmental controls during the peak summer (June–August). The proportion of subjects using a control was related to indoor and outdoor temperatures to demonstrate the size of the effect. The results suggest that the use of controls is also related to thermal sensation and their appropriate use is a significant part of adaptive behaviour to modify the indoor thermal conditions. The results make it possible to predict the effect of temperature on the ventilation rate in naturally ventilated buildings.

Climatic variations in comfortable temperatures: the Pakistan projects

Two thermal comfort surveys in Pakistan are described. One was longitudinal conducted in summer and winter, the other was transverse with monthly surveys over a whole year. The surveys were conducted in five cities each representing a particular climatic region. The use of building controls and clothing is analysed. There is close agreement between the findings of the two surveys despite differences in methodology. The surveys show that there is a definite relationship between indoor comfort and outdoor conditions in line with an adaptive approach to thermal comfort. The current International Standard does not accurately reflect these. Because of the large variations in indoor temperature in many Pakistani buildings, the surveys also indicate the limits of peoples ability to adapt to indoor temperatures.

Development of an adaptive window-opening algorithm to predict the thermal comfort, energy use and overheating in buildings

This investigation of the window-opening data from extensive field surveys in UK office buildings demonstrates: (1) how people control the indoor environment by opening windows; (2) the cooling potential of opening windows; and (3) the use of an ‘adaptive algorithm’ for predicting window-opening behaviour for thermal simulation in ESP-r. It was found that when the window was open the mean indoor and outdoor temperatures were higher than when closed, but it was shown that nonetheless there was a useful cooling effect from opening a window. The adaptive algorithm for window-opening behaviour was then used in thermal simulation studies for some typical office designs. The thermal simulation results were in general agreement with the findings of the field surveys. The adaptive algorithm is shown to provide insights not available using non adaptive simulation methods and can assist in achieving more comfortable, lower energy buildings while avoiding overheating.

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.

Towards an adaptive model for thermal comfort in Japanese offices

ABSTRACT This study investigates the seasonal adaptation to temperature that occurs in Japanese offices, with a view to suggesting an adaptive model for them. Temperatures were measured in 11 office buildings and thermal comfort transverse surveys of occupants were conducted for over a year in the Tokyo and Yokohama areas of Japan. A total of 4660 samples were collected from about 1350 people. The occupants were found to be highly satisfied with the thermal environment in their offices. Even though the Japanese government recommends the indoor temperature setting of 28°C for cooling and 20°C for heating, the comfort globe temperature was found to be 2.6°C lower in cooling mode and 4.3°C higher in heating mode, in line with actual indoor temperatures. The monthly and seasonal variation in the comfort temperature was found to be significantly lower than those in dwellings. The comfort temperature is related primarily to the indoor temperature, but an adaptive relationship can be derived to estimate the indoor comfort temperature from the prevailing outdoor temperature for similar office buildings.

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

Development of a window opening algorithm based on adaptive thermal comfort to predict occupant behavior in Japanese dwellings

Window opening behavior and thermal comfort were monitored in relation to the thermal environment over a 4 year period in the living rooms and the bedrooms of dwellings in the Kanto region of Japan. 36 144 sets of physical and subjective data were collected from 243 residents of 120 dwellings. This paper explores relationships between the different variables in the data. The likelihood of windows being open depended on the three modes of operation of the dwelling, free running (FR), heating (HT) or cooling (CL). In the FR mode, the likelihood was much higher than in either the CL or the HT modes. The likelihood that a window is open correlated well with both indoor temperature and outdoor air temperature in the FR Mode. The indoor comfort temperature correlated well with the running mean of the outdoor temperature. Window opening behavior as predicted by logistic regression analysis is in agreement with the measured data. The deadband of window opening was narrower, and the constraint on window opening was smaller than had previously been found in studies in office buildings. Equations are given to quantify these relations and to enable window opening and comfort temperature to be predicted from outdoor temperature.