Displacement ventilation environments with chilled ceilings: thermal comfort design within the context of the BS EN ISO7730 versus adaptive debate D.L. Loveday a,* , K.C. Parsons b , A.H. Taki c , S.G. Hodder b a Department of Civil and Building Engineering, Loughborough University, Loughborough, UK b Department of Human Sciences, Loughborough University, Loughborough, UK c School of Architecture, De Montfort University, Leicester, UK Abstract The current design standard BS EN ISO7730 [Moderate thermal environments—determination of the PMV and PPD indices and specification of the conditions for thermal comfort, International Standards Organisation (1995)] is based upon the work of Fanger, and essentially comprises a steady-state human heat balance model that leads to a prediction of the sensation of human thermal comfort for a given set of thermal conditions. The model was derived from laboratory-based measurements conducted in the mid-1960s in relatively ‘conventional’ environments. However, a chilled ceiling operated in combination with displacement ventilation represents a more sophisticated environment as compared with the original conditions in which the Fanger model was derived. This raised a question about the applicability of the current standard when designing for thermal comfort in offices equipped with chilled ceiling/displacement ventilation systems. This paper presents findings from an EPSRC-funded study that sought to answer the above question. Human test subjects (184 in total) carried out sedentary office-type work in a well-controlled environmental test room that simulated an office fitted with the above system. Measurements of environmental variables were taken at a number of locations near the subjects, each of whom wore a typical office clothing ensemble. The reported thermal comfort sensations were compared with values predicted from BS EN ISO7730 over a range of system operating conditions. It was shown that the current standard BS EN ISO7730 may be used, without modification, when designing for the thermal comfort of sedentary workers in offices equipped with chilled ceiling/displacement ventilation systems. These findings are interpreted within the context of a proposed modification to thermal comfort design standards that includes adaptive effects, and the influence of BS EN ISO7730 on the development of other radiant surface/displacement ventilation configurations is discussed. # 2002 Published by Elsevier Science B.V. Keywords: Chilled ceiling; Displacement ventilation; BS EN ISO7730; Adaptive thermal comfort. 1. Introduction In industrialised countries, energy usage in buildings is responsible for approximately 50% of carbon dioxide emis- sions. A significant fraction of this energy is consumed to provide comfortable, habitable, conditions indoors. In many countries, the prevailing climate frequently leads to the use of air-conditioning for providing such indoor comfort. How- ever, air-conditioning is recognised as an energy-intensive solution. For example, in the United Kingdom alone, air- conditioning systems consumed about 3% of annual national electricity production in 1995 [2], yet the UK cannot be regarded as possessing a climate that necessitates significant use of air-conditioning. Fears about global warming have added urgency to the search for lower energy techniques for the conditioning of building spaces. Among these techni- ques are displacement ventilation and radiant surface heat- ing or cooling. Displacement ventilation of a room takes place by intro- ducing the supply air at low level and at low velocity. The air enters at a temperature slightly less than that of the average room air, and density differences cause the supply air to form a layer over the floor. Warm sources in the room (occupants, appliances) cause the lower level air to rise and form convective plumes that remove heat and contaminants from the sources. The warm, contaminated air is then extracted at, or near, ceiling level. The system is able to provide an environment of improved air quality as compared with the mixing of air, which occurs in conventional HVAC systems (for the same air flow rate conditions). Also, the same heat loads can be removed for a supply air temperature of Energy and Buildings 34 (2002) 573–579 * Corresponding author. Tel.: þ44-1509-222635. E-mail address: d.l.loveday@lboro.ac.uk (D.L. Loveday). 0378-7788/02/$ – see front matter # 2002 Published by Elsevier Science B.V. PII:S0378-7788(02)00007-5