A normatização brasileira relacionada ao desempenho termoenergético de edificações tem procurado inserir a refletância ou a absortância solar em seus critérios de análise. O objetivo deste artigo é analisar a exatidão e a repetibilidade de medições de refletância com o espectrômetro Alta II, bem como a influência da luminosidade do ambiente e da rugosidade da superfície sobre os valores medidos. Foram realizadas três séries de medições, variando os espectrômetros utilizados, a exposição à luz, e a rugosidade da superfície avaliada. Medições com o espectrofotômetro Lambda 1050 serviram de referência. A análise demonstrou que os resultados podem apresentar imprecisão elevada, com incerteza de ±0,10 nos valores absolutos de refletância solar. Sendo assim, o usuário do espectrômetro Alta II deve utilizá-lo com precaução, considerando tal erro. Também foi possível observar neste estudo que o Alta II pode ser usado especialmente para análise de superfícies planas e lisas. Além disso, deve-se garantir que as medições sejam realizadas com o cuidado de evitar a infiltração de luz através da superfície de contato entre o equipamento e a amostra.

Urbanization and the resulting concentration of people in cities has led to the emergence of Urban Heat Islands (UHI), which is associated with several problems. One strategy for UHI mitigation is the use of cool coatings for pavements and buildings, for instance, on roof tiles. Ceramic roof tiles are widely used in Brazil and in the rest of South America, but they have not been adequately studied regarding their thermal emittance and solar radiation reflectance. These two properties can be used to determine whether or not a roof tile coating can be classed as “cool”, according to the Leadership in Energy and Environmental Design (LEED) certification. In this paper, the solar reflectance, thermal emittance and Solar Reflectance Index (SRI) index were determined for “Portuguese” and “American” colored glazed roof tiles, mostly produced in Brazil. Nineteen glazed roof tiles (from four different producers) with different colors were studied according the LEED certification. The thermal emittance was determined using a portable emissometer and the reflectance spectral curves were measured using a UV–Vis-NIR spectrophotometer. All measurements were performed according to the ASTM standards. The colorimetric coordinates in the visible range (for the D65 illuminant) were determined to evaluate the relationship between the luminous reflectance factor (Y) and the SRI. The optical behavior of the colored glazes for the full range of the solar spectrum was determined using the Kubelka-Munk (K-M) model and the relationship between the absorption (K) and scattering (S) coefficients. The results show that most of the colored glazed tiles did not meet the 2013 LEED requirement, that is, SRI ≥ 39 for roof tiles with a steep slope. A polynomial relationship between the Y factor and the SRI was found (R2 value > 0.95), therefore the tile colors that would probably not qualify for SRI certification could be estimated. The K-M analysis showed that for some glazes there was a high absorption of radiation in the near infrared region, suggesting that the pigments used for these glazes do not exhibit cool properties. Therefore, cool pigments with higher reflectance should be used to improve the performance of the glazes with a low SRI.

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.