Analytical Comparison of the Performance of Simulation Software Programs for Iranian Building Code 19

Efforts of architects and engineers to reduce energy consumption in Iranian buildings have led to develop Building Code 19. It is obvious that complicated calculations especially in large scale buildings are needed for new and high quality numerical analysis software. This kind of numerical calculations can be done using some analytic software programs. The result of this strategy has led to producing some software such as «Mabna» and «BCS19» on the basis of this code. The accuracy and sensitivity of these software programs are very important in choosing the appropriate energy-saving methodology. The main aim of this paper is to analyze the level of accuracy and validity of commercially available software programs which have been developed to help building code 19 such as Mabna and BCS19. High simulation error rates endanger any optimization planning. The validation and verification (V&V) of the accuracy of the Mabna and BCS 19 simulation results is the subject of this paper. In order to achieve this goal، the black box methodology، and ALAC (Act-like-a-customer) technique were chosen to study the software validation، and abstract static analysis method has been chosen in order to study the verification of these software programs. In this technique، the researchers assume themselves as the clients and do as software users do، trying to find discrepancies in the software. A small residential building located in cold and semi-dry climate of Borujerd is chosen as case study and software simulations with Mabna and BCS 19 were carried out as well as numerical calculations based on Building Code 19. Then all the results were compared and the differences between them were analyzed. Software bugs have been studied from different aspects. In verification process، the following results were obtained: (1) both Mabna and BCS 19 had weak graphical user interface (GUI); (2) the impact of thermal bridges are not taken into account in Mabna and BCS 19; (3) Mabna software has an inappropriate way of calculating the thermal performance of the ground floor; (4) software''s thermal data was not updated; (5) both software programs had some errors in the calculation of the correction factors; (6) BCS 19 can not consider the reference values of the elements in the calculation of the total thermal power of the building; and (7) none of the software programs proposed horizontal and vertical shade sizes for the windows. The results show that total heat power of the building was 225. 3 w/K in the numerical calculations; however، it was 216 w/K in BCS19 and 366. 3 w/K in Mabna software. Regarding the fact that the sample building has only 38 m2 area، this difference will be considerable while using such software for larger scale buildings. The results also indicate that the difference between building heat power simulated by Mabna software and the reference value is 2. 5 times more than numerical calculations. These errors can lead the designer to inappropriate solutions with upper costs for building optimization; so finally، some solutions have been proposed for correcting these software programs and optimized use of them.