Journal of Building Physics

The latest architectural trends demand an extensive use of glazed curtain walls running from building floor to ceiling. While glazing poorly controls the heat flow, it is important for viewing, daylighting, and solar design features. In order to evaluate building energy consumption accurately, knowledge of convective heat transfer coefficient (CHTC) distribution over the façade of the building is important. In this article, high-resolution numerical simulations that use three-dimensional steady Reynolds-averaged Navier–Stokes and energy equations are performed. Convective heat transfer coefficient values at the windward facade of five buildings, with rectangular floor plans, and heights of 3, 10, 15, 20–30 stories, have been produced. The influence of building height on CHTC distribution is investigated at Reynolds numbers ranging from 0.7 × 10⁶ to 33 × 10⁶, and a correlation equation as a function of building height and a reference wind velocity is developed. For example, as the height increases from 10.1 to 101 m in the study cases, the surface-averaged convective heat transfer coefficient on the windward façade increases by 55%. The high-resolution spatial distribution of convective heat transfer coefficient over façade of the tallest building indicates that the top-corner zone convective heat transfer coefficient values are higher by 24% and the base-center zone values are lower by 27% compared to the average CHTC value, implying the necessity for zonal treatment.

This work presents the design, construction, and instrumentation of a calorimeter with solar tracking to determine the thermal and optical properties of monolithic glass samples of 15 cm × 15 cm with a maximum thickness of 6 mm. The calorimeter was designed considering an abstract methodology, where the materials, for each of its components, were selected from an evaluation considering its properties and its criteria of functionality. The prototype was constructed and instrumented to quantify the heat losses through each of its walls. The prototype was calibrated to obtain the uncertainty of the heat flows, considering the heat gains and heat losses of the system. The results of the calibration allowed to obtain the uncertainty in the measurement of the heat flow that was estimated as ±0.446 W. On the other hand, to verify the operation of the solar calorimeter, we determined the U-value and solar heat gain coefficient for a 3-mm clear glass sample. The average values obtained for U and solar heat gain coefficient were 6.95 ± 0.9 W m⁻² K⁻¹ and 0.803 ± 0.03, respectively. These values were compared with values reported in the literature, and they have a maximum difference of 7.7%. The uncertainty obtained in the calibration and the values of the characteristic parameters indicate that the solar calorimeter is adequate to obtain the characteristic parameters of monolithic glass samples with optical characteristics similar to the samples of this study.

Two sewage sludge ashes were used as substitutes for cement and their effect on the hygrothermal properties of mortar was examined. Different cement to ash ratios and two ash pre-treatment methods (water washing and grinding) were in focus. The impact of cement replacement by sewage sludge ashes on thermal conductivity, sorption isotherms, water vapour permeability and carbonation was described with standard cement-based mortar as the reference material. Measurement results showed that thermal conductivity decreased by 15% when 30% of the cement was replaced by sewage sludge ash. Water vapour permeability increased as the cement to ash ratio was reduced. Sorption was tested by two methods; although differences in the sorption isotherms of mortars were reported when a climatic chamber method was applied, no differences, or only minor differences, were observed with the desiccator method. Measurements revealed that cement-based mortar possessed a higher content of carbonate than cement-ash-based mortar, and it thus appears that the carbonation rate was higher when the cement content was high.