O objetivo deste trabalho é verificar a influência do índice de massa corpórea (IMC) e da frequência de atividades físicas na sensação, preferência, conforto e aceitabilidade térmica de pessoas que trabalham em escritórios com ventilação híbrida ou que operam com sistema de ar-condicionado central em Florianópolis, SC. Analisaram-se os resultados de 85 estudos de campo (medições ambientais e aplicação de questionários) em três edificações. Os dados foram separados conforme cada modo de operação e subdivididos em dois subgrupos, um de IMC e outro de frequência de atividades físicas; e submetidos a análises estatísticas com as variáveis de conforto térmico. Observou-se uma tendência de os valores de isolamento da vestimenta diminuírem conforme se aumentam os valores de IMC. Sensação, preferência e conforto térmico mostraram relação significativa com os dois modos de operação, quando levados em consideração os valores de IMC. Em geral, indivíduos com maiores IMCs sentem o ambiente mais aquecido, tendem a preferir ambientes mais resfriados e sentem-se mais confortáveis termicamente do que usuários com menores valores de IMC. Os resultados relacionados à frequência de atividades físicas não se mostraram conclusivos.

Building occupants' perception of thermal comfort can be influenced by a number of contextual factors, such as their demographic and anthropometric characteristics, behavioural patterns and cultural aspects. The objective of this work is to investigate the relationship between various contextual factors and the perception of thermal comfort in workplaces, by examining the gap between the current thermal comfort criteria and the actual requirements observed for different groups of occupants. The classic thermal comfort field research design i.e. simultaneous measurements of physical environmental parameters and questionnaire surveys, was implemented for two years in both centralised HVAC and mixed-mode office buildings located in Southern Brazil. Over 7500 questionnaires were completed by occupants of the buildings. Key variables including the participants' gender, age, body mass index, prior exposure to air-conditioning and building ventilation type were investigated in order to identify their association with thermal discomfort in the office workplace. Our results suggest that males, overweight occupants and those who are more frequently exposed to air-conditioning are more likely to express thermal discomfort due to feeling ‘warm’, compared to females, non-overweight occupants and those who were exposed to air-conditioning less frequently. In comparison, females, non-overweight occupants, air-conditioning light users, and occupants of centralised HVAC buildings were more likely to declare ‘cold’ discomfort. We also investigated how those variables were related to the width of thermal comfort zone. The analysis indicates that different groups of occupants require different comfort zones, suggesting that group differences should be considered when designing/operating spaces for diverse groups of occupants.

Studies about thermal comfort in mixed-mode buildings have been performed in order to better understand this type of building and its influence on occupants’ thermal perception. However, there is still no consensus amongst researchers regarding whether mixed-mode buildings should be evaluated separating each mode of operation (natural ventilation or air-conditioning) and whether adaptive thermal comfort theory applies to both modes of operation. Does the mode of operation of a mixed-mode building, ceteris paribus, influence occupant thermal comfort perception? Trying to answer such questions, field studies on thermal comfort were conducted in three mixed-mode office buildings in the city of Florianópolis (a temperate and humid climate), Southern Brazil. Buildings were equipped with mechanical cooling systems and operable windows, both controlled by occupants. Thermal comfort questionnaires were collected at the same time and location that environmental variables were measured by microclimate instruments. Almost 5500 questionnaires were answered by occupants of the three buildings in both modes of operation over the four seasons. Analysis of the results indicated that occupants’ thermal perception was influenced by the mode of operation. Adaptive thermal comfort models were developed for natural ventilation and air-conditioning mode of mixed-mode buildings. This work found no evidence to support a single adaptive model for mixed-mode buildings. During natural ventilation mode, occupants adapted to indoor temperature fluctuations as predicted by the adaptive thermal comfort theory. On the other hand, during air-conditioning operation a weak adaptive relation (indoor comfort temperature vs. outdoor climate) was observed – a range of about 4 °C of indoor temperature fluctuation may be used for the operation of the air-conditioning system without compromising thermal comfort, which could help saving energy. This work is a first step towards building an adaptive model of thermal comfort for Brazilian subtropical climate.

This article aims to assess the effects of gender on requirements for thermal comfort in office buildings. Data were obtained from 83 field studies conducted over 2014 in three office buildings located in Florianópolis, southern Brazil. One of the buildings is fully air-conditioned and the other two operate under mixed-mode strategy, i.e., alternating from air-conditioning to natural ventilation. Data were measured by means of microclimate stations, and the occupants opinions were obtained through a questionnaire. There was no significant difference of clothing insulation for male and female subjects. Significant differences were found for thermal sensation, thermal preference, thermal acceptability and thermal comfort in the central air-conditioned building. In mixed-mode buildings, significant differences were found for thermal sensation and thermal preference responses of male and female subjects. However, during air-conditioning operation in mixed-mode buildings, significant differences were found for thermal preference and thermal acceptability responses of male and female subjects; and during natural ventilation operation, significant differences were found for thermal sensation and thermal preference. In contrast to what some previous studies have found this work indicates the existence of significant differences in the thermal comfort responses of male and female subjects.

In equatorial, hot-humid tropical climates, users of naturally ventilated environments are commonly susceptible to heat discomfort caused by high air temperatures and thus require more air movement to improve thermal comfort. To evaluate the influence of relative humidity and air speed on the occupant's thermal perception, field studies were conducted in naturally ventilated and fan-assisted classrooms in São Luis City, North-Eastern Brazil. Indoor environmental variables were measured alongside questionnaires, focusing on thermal environment and air movement evaluation. The results indicated that relative humidity had a significant negative impact on thermal perception when the operative temperature was above 30 °C, while airspeed played a key role in reducing thermal discomfort. Despite the contribution of internal air movement, it was concluded that, when the indoor operative temperature exceeded 31 °C, mechanical cooling is required to achieve thermal comfort. The results also indicated the great acceptability of indoor conditions, as well as the influence of environmental variables on student's thermal perception in naturally ventilated spaces.

Recognizing the value of open-source research databases in advancing the art and science of HVAC, in 2014 the ASHRAE Global Thermal Comfort Database II project was launched under the leadership of University of California at Berkeley's Center for the Built Environment and The University of Sydney's Indoor Environmental Quality (IEQ) Laboratory. The exercise began with a systematic collection and harmonization of raw data from the last two decades of thermal comfort field studies around the world. The ASHRAE Global Thermal Comfort Database II (Comfort Database), now an online, open-source database, includes approximately 81,846 complete sets of objective indoor climatic observations with accompanying “right-here-right-now” subjective evaluations by the building occupants who were exposed to them. The database is intended to support diverse inquiries about thermal comfort in field settings. A simple web-based interface to the database enables filtering on multiple criteria, including building typology, occupancy type, subjects' demographic variables, subjective thermal comfort states, indoor thermal environmental criteria, calculated comfort indices, environmental control criteria and outdoor meteorological information. Furthermore, a web-based interactive thermal comfort visualization tool has been developed that allows end-users to quickly and interactively explore the data.

The Griffiths method is widely used in thermal comfort studies to derive building users’ comfort temperature, or thermal neutrality as it is sometimes known. A single value (so called the Griffiths Constant, typically 0.5/°C) is prescribed as a representation of thermal sensitivity of building occupants to indoor temperature variations, which in turn is used to estimate indoor thermal neutrality from a subject's actual thermal sensation vote at a measured room temperature. Despite the Griffiths Constant of 0.5/°C having been used widely across the thermal comfort research literature and in some generic standards, the constant was derived exclusively from office building data and its applicability across different typologies is yet to be rigorously validated. The objective of this study is to quantify how sensitive people are to temperature variations inside a building, and to investigate if thermal sensitivity differs between different contexts (including building typologies, modes of ventilation, outdoor climatic types, and genders). A collection of thermal comfort field studies in different building typologies containing around 11,500 datasets was used to statistically derive building users’ thermal sensitivity, i.e. the rate of change in thermal sensation per unit change in indoor temperature within a day. Our results suggest that occupant thermal sensitivity does vary depending on building typologies and building ventilation mode. In naturally ventilated spaces users are about half as sensitive to temperature variations as in air-conditioned spaces. Age, gender and climate are found to be factors that can also influence thermal sensitivity of building occupants. Our findings imply that reliance on a universal thermal sensitivity value, the Griffiths Constant, in comfort temperature (neutrality) calculations should be avoided because it is in fact a variable.

O objetivo deste trabalho é comparar as respostas subjetivas de usuários de escritórios localizados no clima subtropical brasileiro, ao longo das quatro estações climáticas, com os modelos de conforto térmico (analítico e adaptativo) da ASHRAE 55 (2017). Estudos de campo sobre conforto térmico foram realizados em quatro edificações de escritórios em Florianópolis/SC durante dois anos. Uma das edificações operou com sistema de ar-condicionado central, enquanto as demais edificações operaram com ventilação híbrida (usuários controlaram o sistema de ar-condicionado e a operação de aberturas). Questionários de conforto térmico foram aplicados, ao mesmo tempo e no mesmo espaço, em que medições das variáveis ambientais (temperatura do ar, umidade relativa, temperatura radiante média e velocidade do ar) foram realizadas. Mais de 7.500 respostas dos usuários foram coletadas durante os estudos de campo, as quais foram comparadas com os modelos da ASHRAE 55. O modelo analítico superestimou as sensações de frio e de calor dos usuários e também não estimou adequadamente a porcentagem de insatisfeitos em todas as estações climáticas e edificações. Durante a operação da ventilação natural, os usuários das edificações com ventilação híbrida se adaptaram às variações térmicas internas de acordo com o modelo de conforto térmico adaptativo.

Air conditioning (AC) systems have been increasingly adopted as the main cooling strategy in Brazilian buildings, and this may affect people's response to hot indoor spaces. A field study was conducted in naturally-ventilated classrooms located in the northeast region of Brazil with the purpose of evaluating the subjective responses of the students as a function of different thermal backgrounds in relation to the use of AC. Indoor microclimatic variables were measured and a questionnaire was applied to the students, in which the thermal perception, air movement perception and cooling strategy preference were recorded. The thermal background of the participants in relation to AC was classified as follows: recent prior exposure (exposure to AC 1 h before the field survey), long-term exposure (routine experience of AC), and hours of AC exposure daily (in cases where long-term exposure was declared). Long-term exposure to AC influenced the thermal perception of the students and significant differences between exposed and unexposed students were observed for a temperature of 28–30 °C (standard effective temperature - SET). The influence of recent prior exposure to AC was negligible compared to that of long-term exposure. Among the students with experience of long-term exposure to indoor AC, those who declared exposure to 12 or more hours daily responded with the warmest thermal sensation (TS) values and the highest percentage of preference for AC as a cooling strategy. Hot discomfort was a key factor in the influence of long-term exposure on human thermal perception.