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.