The indices of thermal comfort that constitute international standards, such as ISO 7730 and norms suggested by technical publications such as ASHRAE Fundamentals, are PMV, PPD, and T{sub oc}. The aim of this paper is to present similar indices developed from field studies. The studies were made at a school in Florianopolis, Brazil, and consist of more than 1,200 data points. The environmental variables were measured, and the metabolic rate and the thermal insulation of the clothing were estimated from existing tables. Thermal sensation votes were collected for all the students by means of specific questionnaires. The main conclusions are: There is good agreement between the sensations related by the subjects and those obtained from predictions determined by regression analysis; the studies provide one with a different understanding of dissatisfaction with a thermal environment; and when determined from the votes of dissatisfied people, the comfort temperature offers the advantage of showing one the percentage of people who are not comfortable.

Este trabalho discute os limites dados para a velocidade do ar pelas normas ASHRAE 55 (2004) e ISO 7730 (2005). Para tal, realizou-se uma análise comparativa entre os valores-limite para a velocidade do ar definidos por essas normas e as respostas dos usuários em relação à preferência e aceitabilidade do movimento do ar obtidas em experimentos de campo realizados em Maceió/AL. Resultados indicam que ambas as normas especificam valores para a velocidade do ar inferiores aos desejados pelos usuários. Os resultados da preferência do movimento do ar indicam que significativa percentagem dos usuários demanda “maior movimento do ar”. Quando associada às respostas da aceitabilidade do movimento do ar, a insatisfação dos usuários ficou mais evidente, assim como a demanda por maior velocidade do ar. O mesmo movimento de ar, considerado como inaceitável em climas frios e temperados, é desejado pelos usuários em climas úmidos. Nesse contexto, a aplicabilidade de limites máximos para a velocidade do ar provenientes de estudos com características climáticas diferentes deve ser evitada. Tais limites devem vir de resultados de experimentos de campo em ambientes naturalmente ventilados, onde os usuários possam utilizar de oportunidades adaptativas para reestabelecer o conforto térmico. Futuras normas brasileiras devem focar em tais questões, visando limites de velocidade que correspondam à expectativa dos usuários em climas quentes e úmidos.

According to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), it is clear that the buildings sector presents the biggest potential for deep and fast CO₂ emission reductions on a cost-effective basis. Interestingly, this assessment was premised exclusively on technical (engineering) measures, but ignored completely the behavioural and lifestyle dimensions of energy consumption in the buildings sector. Behavioural change in buildings, however, can deliver even faster and zero-cost improvements in energy efficiency and greenhouse gas (ghg) emission reductions. With this in mind, designers are beginning to shift their attention to how they can widen the range of opportunities available in a building to provide comfort for the occupants, both in new-build and retrofit contexts. This in turn has re-awakened an interest in the role of natural ventilation in the provision of comfort. This discussion about adaptive comfort raises several questions, including the following: How can we shift occupants' comfort expectations away from the static indoor climates of the past towards the more variable thermal regimes found in naturally ventilated buildings? Are building occupants ‘addicted’ to static environments, i.e. air-conditioning (AC)? If so, how tolerant or compliant will they be when the thermally constant conditions provided by AC are replaced by the thermally variable conditions that characterize naturally ventilated spaces? Does the frequency of prior exposure to AC bias building occupants' thermal expectations and, if so, what are the implications of this bias for their acceptance of naturally ventilated indoor climates? Does prior exposure to AC lead building occupants to actually prefer AC over natural ventilation? This article addresses these questions in the context of a large field study of building occupants in a hot and humid climate zone in Brazil (Maceio). The temperature preferences registered on 975 questionnaires in naturally ventilated buildings are statistically analysed in relation to occupants' prior exposure to AC in their workplaces.

The objective of this paper was to perform an analysis on thermal acceptability in naturally ventilated (NVB) and air-conditioned buildings (ACB) located in hot and humid climates in Brazil. Experiments were carried out in April and November 2005 with 1.301 questionnaires based on ISO 10551:1995(E). Indoor and outdoor climatic variables were monitored simultaneously. The results revealed that 53% of the occupants of NVB and 78% of ACB were thermally satisfied. However, some restrictions were observed with the applications of the following methodologies: ISO/FDIS 7730:2005(E); ANSI/ASHRAE Standard 55:2004; Adaptive Temperature Limits (ATG) and prEN15251: 2005(E). Differences were observed between thermal sensation (TSV) and predicted mean vote (PMV) and between the subject's percentages expressing thermal unacceptability of the environment and the PPD calculated according to ISO/FDIS 7730:2005(E).

In hot humid climates, natural ventilation is an essential passive strategy in order to maintain thermal comfort inside buildings and it can be also used as an energy-conserving design strategy to reduce building cooling loads by removing heat stored in the buildings thermal mass. In this context, many previous studies have focused on thermal comfort and air velocity ranges. However, whether this air movement is desirable or not remains an open area. This paper aims to identify air movement acceptability levels inside naturally ventilated buildings in Brazil. Minimal air velocity values corresponding to 80% and 90% (V80 and V90) air movement acceptability inside these buildings. Field experiments were performed during hot and cool seasons when 2075 questionnaires were filled for the subjects while simultaneous microclimatic observations were made with laboratory precision. Main results indicated that the minimal air velocity required were at least 0.4 m/s for 26 °C reaching 0.9 m/s for operative temperatures up to 30 °C. Subjects are not only preferring more air speed but also demanding air velocities closer or higher than 0.8 m/s ASHRAE limit. This dispels the notion of draft in hot humid climates and reinforce the broader theory of alliesthesia and the physiological role of pleasure due to air movement increment.

The Brazilian Federal Government has been recently promoting energy-conservation initiatives, most notably the ‘Thermal Performance in Buildings – Brazilian Bioclimatic Zones and Building Guidelines for Low-Cost Housing’ and the ‘Federal Regulation for Voluntary Labelling of Energy Efficiency Levels in Commercial, Public and Service Buildings’. These new regulations provide information for designers based on Brazil's climate requirements, with specific advice related to lighting systems, HVAC and the thermal envelope of buildings. Nevertheless, requirements for naturally ventilated indoor environments appear as an open category without clear criteria. To address this, the paper proposes guidelines for naturally ventilated environments in which specific thermal and air movement acceptability goals must be achieved. The guidelines are based on results from field experiments in non-residential naturally ventilated buildings in different climatic zones as well as drawing on other studies. The proposed guidelines consider occupants' adaptive potential as well as thermal and air movement acceptability. Combining thermal acceptability with air movement acceptability is a key design challenge. Permissible operative temperature ranges are based on the ASHRAE 55 adaptive comfort standard, and minimum air velocity requirements within the occupied zone are specified. Considerations also included ‘active’ occupants and specific control over openings and fans.

In the ASHRAE comfort database [1], underpinning the North American naturally ventilated adaptive comfort standard [2], the mean indoor air velocity associated with 90% thermal acceptability was relatively low, rarely exceeding 0.3 m/s. Post hoc studies of this database showed that the main complaint related to air movement was a preference for ‘more air movement’ [3], [4]. These observations suggest the potential to shift thermal acceptability to even higher operative temperature values, if higher air speeds are available. If that were the case, would it be reasonable to expect temperature and air movement acceptability levels at 90%? This paper focuses on this question and combines thermal and air movement acceptability percentages in order to assess occupants. Two field experiments took place in naturally ventilated buildings located on Brazil’s North-East. The fundamental feature of this research design is the proximity of the indoor climate observations with corresponding comfort questionnaire responses from the occupants. Almost 90% thermal acceptability was found within the predictions of the ASHRAE adaptive comfort standard and yet occupants required ‘more air velocity’. Minimum air velocity values were found in order to achieve 90% of thermal and air movement acceptability. From 24 to 27 °C the minimum air velocity for thermal and air movement acceptability is 0.4 m/s; from 27 to 29 °C is 0.41–0.8 m/s, and from 29 to 31 °C is >0.81 m/s. These results highlight the necessity of combining thermal and air movement acceptability in order to assess occupants’ perception of their indoor thermal environment in hot humid climates.