Increasing the thermal resistance of masonry wall systems is one of the effective ways to reduce energy consumption in the operation of masonry buildings. This increase is also demanded by newer, more stringent energy codes. However, the effective thermal resistance ( R-value) of masonry walls is affected by many factors, such as thermal bridging, which occurs in places where highly conductive structural components penetrate insulating materials. Thermal bridging is common when connecting masonry veneers to structural backup walls. Furthermore, quick and precise methods for estimating the R-value are needed for thermal design improvements and code-compliance calculations. This study presents a comprehensive literature review on key factors that influence the overall thermal performance of masonry walls, methods to effectively estimate and measure R-values, and improvements in thermal design. In addition to identifying the main technical and practical challenges and the corresponding progress made on each front, key design considerations, such as code compliance, material properties, insulation types, and location, as well as special ties and shelf angles types, are also discussed. This study summarizes critical information and recommendations that will help improve the thermal design of masonry walls, hence reducing the energy consumption of buildings.
Air leakage is one of the main influencing factors in buildings’ thermal performance. The adverse effects of poor air leakage include higher energy costs, consumption in space heating and cooling, poor thermal comfort, corrosion, and the growth of molds due to air leakage induced condensation. The main objective of this study is to investigate the characteristics of air leakages of Canadian homes related to construction methods, age, size and climatic zones. The air leakage test results of 226,000 dwellings in three provinces of Canada were analyzed. Statistical analysis was utilized to compare the mean of air leakage with respect to different factors. Generally, the air leakage decreased by 40% in the period from 1960 until 2018, which has shown a remarkable effect of new construction techniques on air leakage. Investigations also indicated that the average air leakage rate of homes constructed by using the onsite technique is approximately 25% to 60% higher than those prefabricated in modular or panels, varying with respect to the workmanship and construction quality control. This study concluded that the prefabricated construction techniques could decrease the air leakage rate significantly, which will have a remarkable effect on buildings’ thermal performance as well as home’s heating and cooling costs. The findings contribute to estimating the effects of influencing factors on air leakage, also it is useful in performance simulations, HAVC sizing and energy management. And recommend the use of the prefabricated in modular or panel’s construction method to achieve better and acceptable air leakage performance.
The airtightness of buildings has a significant impact on buildings’ energy efficiency, maintenance and occupant comfort. The main goal of this study is to provide an evaluation of the air leakage characteristics of dwellings in different regions in Canada. This study evaluated the key influencing factors on airtightness performance based on a large set of measured data (73,450 dwellings located in Canada with 11 measurement parameters for each). Machine learning models based on multivariate regression (MVR) and Random Forest Ensemble (RFE) were developed to predict the air leakage value. The RFE model, which shows better results than MVR, was used to evaluate the effect of the ageing of buildings. Results showed that the maximum increase in air leakage occurs during the first year after construction – approximately 25%, and then 3.7% in the second year, after which the increase rate becomes insignificant and relatively constant – approximately 0.3% per year. The findings from this study can provide significant information for building designs, building performance simulations and strengthening standards and guidelines policies on indoor environmental quality.
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