This paper describes the development of a web-based HVAC&R design and decision-making model and system. The aim of this model and system is to provide a free and easy way for HVAC&R professionals in their design and decision-making process in engineering projects. This model is validated on a practical project in Changsha city, China. Finally, this paper examines the advanced feature of this system that makes it a useful tool and points out its further development.