Effect of Thermal Bridges in Insulated Walls on Air-Conditioning Loads Using Whole Building Energy Analysis

Abstract

Thermal bridges in building walls are usually caused by mortar joints between insulated building blocks and by the presence of concrete columns and beams within the building envelope. These bridges create an easy path for heat transmission and therefore increase air-conditioning loads. In this study, the effects of mortar joints only on cooling and heating loads in a typical two-story villa in Riyadh are investigated using whole building energy analysis. All loads found in the villa, which broadly include ventilation, transmission, solar and internal loads, are considered with schedules based on local lifestyles. The thermal bridging effect of mortar joints is simulated by reducing wall thermal resistance by a percentage that depends on the bridges to wall area ratio (TB area ratio or A mj /A tot ) and the nominal thermal insulation thickness (L ins ). These percentage reductions are obtained from a correlation developed by using a rigorous 2D dynamic model of heat transmission through walls with mortar joints. The reduction in thermal resistance is achieved through minor reductions in insulation thickness, thereby keeping the thermal mass of the wall essentially unchanged. Results indicate that yearly and monthly cooling loads increase almost linearly with the thermal bridge to wall area ratio. The increase in the villa's yearly loads varies from about 3% for A mj /A tot = 0.02 to about 11% for A mj /A tot = 0.08. The monthly increase is not uniform over the year and reaches a maximum in August, where it ranges from 5% for A mj /A tot = 0.02 to 15% for A mj /A tot = 0.08. In winter, results show that yearly heating loads are generally very small compared to cooling loads and that heating is only needed in December, January and February, starting from late night to late morning. Monthly heating loads increase with the thermal bridge area ratio; however, the variation is not as linear as observed in cooling loads. The present results highlight the importance of reducing or eliminating thermal bridging effects resulting from mortar joints in walls by maintaining the continuity of the insulation layer in order to reduce energy consumption in air-conditioned buildings.

Patents Analysis of Thermal Bridges in Slab Fronts and Their Effect on Energy Demand

“…Results showed an influence between 5 and 13% on the heating energy demand, and of 1% in cooling energy demand. Zedan et al [34] studied the effect of thermal bridges generated by mortar joints, capable of causing even an increase of 15% in the internal loads of the building. Song et al [35] studied thermal bridges in metal panel curtain wall systems, proposing different options that achieved a 68% reduction in the heat loss by 68%.…”

Unveiling the mural painting art of Almada Negreiros at the Maritime Stations of Alcântara (Lisbon): diagnosis research of paint layers as a guide for its future conservation

“…It must be noted that within the main hall, the mural panels span over two stories high, which positions the floor joint in the middle of the paintings as illustrated in Figure 4. The most deteriorated areas of the mural panels are aligned with this junction favoring the occurrence of thermal bridges (Jedidi & Benjeddou 2018;Zedan et al 2016).…”

Thermal resistance of masonry walls: a literature review on influence factors, evaluation, and improvement

“…Another suggestion was to replace the side mortar with mechanical interlocking. Zedan et al (2016) conducted whole building simulations to study the thermal bridges primarily caused by mortar joints between insulated building blocks. Results showed that the effects of thermal bridges resulting from mortar joints is significant and may cause an increase in the annual heating or cooling load by 11%.…”