Search

In this paper, a newly developed heat and moisture transfer model for green envelopes is integrated in a transient building simulation program (TRNSYS) in order to investigate its dynamic performances coupled with a multizone building code. On the one hand we focus on the understanding of the coupled heat and mass transfers between green envelopes and the building; and on the other hand we study the model accuracy to assess the vegetation impacts together with building design. At first, the model reliability is verified through experimental comparisons during a summer period. Then, the developed simulation tool is used to assess the impacts of green walls on building energy performance. Since this model involves different hygrothermal transfer phenomena, the detailed numerical model results are analyzed to determine the weight of each phenomenon: evapotranspiration, shading effect and additional thermal resistance of green roof or wall. The results highlight the thermal benefits in summer and winter, especially for the west walls. The analysis of the different transfer mechanisms show that the foliage shading reduces the surface temperature variation whereas the evapotranspiration ensures the passive cooling when the water availability is sufficient. [ABSTRACT FROM AUTHOR]

Abstract: Energy performance of air conditioned buildings and summer comfort can be improved with high solar reflectance and high emittance of building envelopes. Widely used for roofs, this technique known as cool roof, has a direct impact on the external surface temperatures peaks which reduces both heat transfer to the building and to the environment. In this paper, this technique used with façades is experimented in a confined environment similar to a typical urban scene. This reduced-scale of 4 street canyon rows is designed in order to give realistic measurements of thermal confinement. Then, the temperatures of a street canyon with brown cool selective paint façades are compared with a standard brown coating on another street façades, and with an asymmetrical configuration. The analysis of thermal effects on both buildings and outdoor environments gives interesting prospects for urban heat island mitigation. [Copyright &y& Elsevier]

The single family home market is facing increasing challenges in managing environmental issues. The required objective of building energy performance can be achieved by limiting extra cost, integrating building design, and using the most appropriate and readily available materials. However, standard computations, such as the French building energy code used here, require vocational expertise that involves managing separate processes and numerous design variables. The design is therefore restricted to well-known techniques, especially for small constructions. In this paper, the usual stakeholder constraints and possible developments in design practice are considered through the use of real product databases and vocational tools to calculate construction costs. In the first stage, which takes into account cost and energy demand, an integrated approach to building envelope design is detailed, including a semantic system to automate the process. Then an optimization method (a genetic algorithm) is proposed to assess energy performance and the cost of the building envelope. This process is illustrated as a case study for a single family house. The results highlight various optimal solution domains specific to the case study, which can be further managed through a decision support system. [ABSTRACT FROM AUTHOR]