RACA Journal I April 2026 www. refrigerationandaircon. co. za 5
LOCAL INNOVATION
INSIDE BSIMAC: ENGINEERING RIGOUR, PERFORMANCE AND A PRACTITIONER-LED PHILOSOPHY
By Eamonn Ryan
In the first part of this article published in March, BSIMAC’ s origins and dualfunction design / simulation capability highlighted how a locally developed tool earned credibility in South Africa’ s HVAC and building-energy market. But its staying power lies deeper than market adoption alone. business
At the core of BSIMAC is a development philosophy shaped by day-to-day engineering practice rather than academic abstraction – one that prioritises modelling flexibility, computational efficiency and transparent, defensible results. These technical differentiators have enabled the software to handle complex real-world buildings, support rapid design iteration and maintain robustness in compliance-critical applications.
What follows is a closer look at the engineering choices, performance strategies and data architecture that distinguish BSIMAC from both simplified load calculators and heavyweight simulation engines.
TECHNICAL DIFFERENTIATORS AND DEVELOPMENT PHILOSOPHY
• Advanced component modelling: BSIMAC is developed to handle a wide spectrum of building types( houses, multi-storey office buildings, shopping centres, churches, cinemas, hospitals, prisons) and HVAC systems( split-units, packaged units, chilled-water systems, and bespoke systems). The software’ s modelling engine allows for detailed definition of building envelope elements – walls, roofs, glazing, internal heat gains, ventilation – and equipment performance.“ This level of flexibility allows users to capture real-world design variation instead of being forced into simplified templates. HVAC design and building architecture can differ enormously from one project to the next, so the software has to be flexible enough to model unconventional layouts and systems. That’ s always been a core principle in how I develop BSIMAC.”
• Performance and‘ what‐if’ capability – Johannsen highlights the importance of software performance – by using iterative methods and advanced programming, BSIMAC can execute annual simulations in minutes rather than hours. This is a major productivity gain when doing built-environment modelling where multiple scenarios must be compared, for example: what happens if I increase insulation, change glazing type or vary HVAC efficiency.“ Another important feature is that BSIMAC stores all the intermediate calculation results. So, if a user wants a different report after the initial run, there’ s no need to rerun the entire simulation. That’ s a major advantage over many large simulation engines, where even a small change forces a full re-run.”
• Robust error-trapping and data-banks: Recognising that complex models can easily be mis-specified, BSIMAC features two levels of error-checking:
○ Immediate validation at the data-entry level( ensuring inputs stay within valid ranges, though still permitting‘ extreme’ values when required)
○ A deeper‘ job-level’ compatibility check when a simulation is about to run – ensuring that interdependent inputs do not conflict. When conflicts are detected, the system reports both the nature of the error and guidance on how to fix it.
Alec Johannsen.
This approach has helped BSIMAC achieve high stability and robustness in day-to-day practice, reducing‘ software crash’ risk and improving user confidence.
In addition, BSIMAC boasts comprehensive built-in data banks including:
• Design weather datasets( peak cooling / heating days)
• Full hourly weather files for locations worldwide
• Materials library( building and insulation materials, including air spaces)
• Construction library( walls, roofs, floors)
• A tool to generate new climatic datasets for any global site, by entering minimal parameters and pressing a button
• Direct links within the software to international weather‐file repositories
These databases dramatically reduce the setup burden, especially for users working in new geographic regions or unfamiliar climates.
MARKET POSITION AND PRACTITIONER ADOPTION With approximately 150 users currently licenced, BSIMAC may not have the scale of global simulation behemoths – but its niche is well defined: South Africa and southern Africa, HVAC consulting firms, architects requiring certified compliance simulation, and engineers needing fast‘ what-if’ design / simulation tools.
Supplied by Alec Johannsen
RACA Journal I April 2026 www. refrigerationandaircon. co. za 5