Design optimization of energy conserving building envelopes

Abstract

The aim o f this dissertation is to present the framework, development, validation, and implementation o f a reliable thermal optimization model for the design o f the physical components o f buildings. The research was motivated by the need found for design information to aid building designers in their decision making purposes, especially in the early stages o f the design process. Available energy simulation models are powerful tools for the evaluation o f the thermal performance o f buildings. They can provide extensive performance information on the selected building. However, such models assume a predetermined solution, and different design alternatives can be evaluated only one at a time. The model developed, termed ENEROPT (ENERgy OPTimization), optimizes the thermal performance o f buildings based on hourly simulation o f the thermal behavior that minimizes reliance upon mechanical heating and air-conditioning systems. The building thermal optimization model couples a direct search optimization technique to the thermal analysis o f buildings. The focus o f the research was on the thermal optimization o f the physical components of the building envelope as the main design variables. The model was applied to the design optimization o f multi-zone air-conditioned office and residential buildings as well as a single zone unconditioned residence in four U.S. and two Saudi Arabian climatic regions. The optimization results revealed significant reductions, not only in the annual energy requirements, but also in the building peak heating and cooling loads, especially for skin-load dominated structures such as residences and small offices. Such improvements in building thermal performance result in less operating costs, as well as less initial system costs due to smaller HVAC system required in air-conditioned buildings. In the case o f the unconditioned building, the optimization procedures indicate a decrease in the number o f thermal discomfort degree-hours In both cases, the results o f optimization show a positive impact on the environment as well. This demonstrates the potentials o f implementing systematic approaches in the building design process.