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.

Em climas quentes e úmidos, é sabido que a velocidade do ar exerce um papel importante no conforto, promovendo as trocas térmicas entre nossa pele e o ambiente. Com isso em mente, o objetivo principal deste trabalho é avaliar o efeito de valores elevados de velocidade do ar (0,20-1,35 m/s) no conforto térmico de ocupantes em salas de aula com sistema de condicionamento híbrido (ar condicionado + ventiladores de teto), localizadas em uma região de clima quente e úmido. Para esse fim, questionários foram aplicados em alunos de graduação, simultaneamente às medições instrumentais ambientais (temperatura do ar, umidade relativa, temperatura de globo e velocidade do ar). Os resultados sugerem que, para as condições do experimento e em ambientes condicionados artificialmente, os usuários podem aceitar, e até preferir, a velocidade do ar acima de 0,90 m/s, se associada a valores de temperatura mais elevados (25 a 28 ºC) em climas quentes e úmidos.

The aim of this paper is to identify which method to assess thermal comfort is the most appropriate to be used in hybrid commercial buildings located in hot and humid summer climate. Three methods to assess thermal comfort were analysed: (1) ASHRAE 55 for determining acceptable thermal conditions in occupied spaces, (2) ASHRAE 55 for determining acceptable thermal conditions in naturally ventilated spaces and (3) Givoni's chart for hot and humid climates. Models with two geometries, two room sizes per geometry, two solar orientations and three window areas per model were analysed. Simulations were performed using the EnergyPlus programme, with the TRY climate file of Florianópolis. Thermal comfort was evaluated applying the simulations output data into the three methods. Thus, the amount of time (number of hours per year) in which the use of air-conditioning is necessary to bring thermal comfort for the users throughout the year was determined using each method. Such number of hours of use of air-conditioning was also compared with the pattern of use of air-conditioning observed in Florianópolis. The main conclusion is that the most suitable method for use in hot and humid summer climates is the method proposed by Givoni.

ASHRAE Standard 55 is widely used to assess thermal comfort in buildings worldwide. The main purpose of this paper is to evaluate the adaptive method application proposed by ASHRAE 55 in two different climates in Brazil. This method relates the conditions for comfort to the “prevailing mean outdoor air temperature”. The currently available version of the Standard allows for linear and exponential methods to calculate the “prevailing mean”, and both are tested to establish the acceptability zones. The results indicate that choosing any of the methods to calculate the prevailing mean outdoor air temperature gives similar results when the temperature amplitudes are small; but it can lead to different limits of acceptability, and consequently sum of discomfort hours, when significant day-to-day temperature variations are present. In addition, the results indicate that it is possible to find significant percentages of thermal acceptability from previous studies below the lower limit of acceptability proposed by the Standard. As a result, a “clo adjustment zone” is suggested.

The aim of this paper is to review the literature on human thermal comfort in the built environment. First an overview about the subject area is presented. This is followed by a review of papers published in the last 10 years that examine the various sub-areas of research related to human thermal comfort. Some remarkable works about both the Fanger's and adaptive thermal comfort models are also discussed. This review does not contain simulation works and/or experimental studies without subjective results of people. As a result of the literature review, 466 articles were classified and grouped to form the body of this article. The article examines standards, indoor experiments in controlled environments (climate chamber) and semi-controlled environments, indoor field studies in educational, office, residential and other building types, productivity, human physiological models, outdoor and semi-outdoor field studies. Several research topics are also addressed involving naturally ventilated, air-conditioned and mixed-mode buildings, personalized conditioning systems and the influence of personal (age, weight, gender, thermal history) and environmental (controls, layout, air movement, humidity, among others) variables on thermal comfort.

Currently, there is a rising trend for commercial buildings to use air conditioning to provide indoor thermal comfort. This paper focuses on the impact of prolonged exposure to indoor air-conditioned environments on occupants’ thermal acceptability and preferences in a mixed-mode building in Brazil. Questionnaires were administered while indoor microclimatic measurements were carried out (i.e., air temperature, radiant air temperature, air speed and humidity). Results suggest significant differences in occupants’ thermal acceptability and cooling preferences based on thermal history; differences were found between groups based on different physical characteristics (i.e., different gender and body condition). The findings also indicated a significant potential to implement temperature fluctuations indoors when occupants are exposed to air conditioning environments in warm and humid climates.