Complex geometries in buildings have become more common in contemporary architecture. Concurrently, sustainable design is a rapidly growing segment of the building industry. One of the biggest challenges for the designers of sustainable buildings is achieving energy efficient designs utilizing parametric and/or creative configurations.

It is often difficult to accurately predict the energy performance of buildings that incorporate complex geometry in architectural design. The main reason behind this is that most simulation programs are designed for box-shaped buildings. Even building codes or standards, such as ASHRAE 90.1, do not account for issues regarding complex geometry. (Ko, 2012) Therefore in some cases, there are no feasible ways of considering the code or energy simulation.

This paper addresses the complex geometry issue in two parts: 1) a brief review of the current energy codes and standards in regards to angular dependence of SHGC for glazing property requirements and 2) a comparison of several building energy simulation programs in modelling of complex façades. In the first half, the limitation of energy codes and standards such as ASHRAE 90.1 were discussed. In the second half, several building simulation programs (Ecotect, eQUEST, IES-VE, DesignBuilder and EnergyPro) were investigated to check how the programs reflect the subject discussed in the first half, (i.e. if inclination of glazing had been properly accounted for). In the review, two issues were considered: if the program itself either imports or calculates the SHGC at different angles of incidence for each glazing system, and if the complex façade geometry can be modelled accurately in the software programs. At the end, a case study with glass dome was simulated in different programs and the results were compared.