Trial / Demo
To meet the demands of energy efficiency compliance, net-zero targets and superior operational efficiency, AEC professionals have long required building performance modelling that is accurate and flexible. For over three decades, APACHE has been the gold standard and is the core of IES’s software commitment to precise, dynamic simulation.
In a market where other simulation engines are often open source or owned by governments, APACHE's value proposition is clear: it is a commercially maintained, continually developed physics engine offering unrivalled flexibility and the detailed accuracy necessary to deliver buildings that perform for critical, real-world projects.
IESVE 2025 delivered several powerful upgrades to the APACHE simulation engine. It now supports a fresh wave of robust new modelling capabilities for emerging low-carbon systems, and passive strategies. These engine advancements were seamlessly integrated into IESVE with the fast, automated workflows and clear, intuitive visuals that users will be familiar with, enabling quicker analysis and more confident decision making.
What is the APACHE Simulation Engine?
APACHE is IES’ core simulation engine, renowned globally for its technical robustness and compliance. It drives every critical dynamic thermal simulation within IESVE, utilising the fundamental laws of physics to predict energy consumption, indoor environmental quality (IEQ) and carbon emissions.
Why is APACHE Unique?
Unlike other simulation engines, APACHE is wholly developed and maintained by IES. This ownership grants us complete control over its developmental roadmap, guaranteeing rapid alignment with evolving global standards and zero-carbon design needs. Our internal team of physics experts continuously refines, audits and optimises APACHE, guaranteeing rapid responses to market needs and unmatched speed, precision and scalability.
IESVE 2025 Enhancements
The latest IESVE 2025 releases, including Feature Pack 1 and other updates, made APACHE faster, smarter and more accurate, while maintaining the scientific credibility that defines the IES brand. It reaffirms APACHE's role as the definitive platform for achieving a sustainable, smart built environment. And delivers critical new capabilities that help engineers, architects and sustainability consultants to accurately model and optimise high-performance designs:
- Advanced Thermal Bridging Analysis
This enhancement to IES’s APACHE engine uses advanced solar air temperature (sol-t) calculations, combining outside dry-bulb temperature, solar absorption, and long-wave radiation losses. The result is a true physics-based representation that is much more accurate than the simplified external air temperature method used elsewhere, giving us the technical superiority you’d expect.
These improvements make it easier than ever to account for thermal bridging using either Psi/Chi or Y-values, alongside the existing composite layer method, giving consultants the flexibility to test which approach works best. This helps bridge the performance gap between design and reality, and future proofs the VE’s ability to comply with key global codes like ASHRAE 90.1, NECB, and UK Part L.
- Modeling of Phase Change Materials (PCM)
IES’s APACHE engine was significantly enhanced as part of this work to dynamically simulate Armstrong® PCM Templok® ceilings, accurately capturing their heat absorption and release cycles at each timestep. This integration enables true physics-based modelling of passive thermal storage, improving prediction of indoor comfort, HVAC performance, and overall building energy efficiency.
- Complex Heat Acquisition & Rejection Coil (HARC) Systems
The IESVE HARC solution was backed by significant investment and expertise, including major upgrades to our APACHE engine, ensuring robust, flexible, and future-ready modelling for users. Development was informed by best practice from top engineering firms and direct user feedback, ensuring it fits seamlessly into real-world workflows and delivers practical value.
To meet the demands of complex facilities like hospitals and laboratories, the APACHE engine was enhanced to support modelling of both the acquisition (recovery) of heat from exhaust air or other sources and rejection (removal) of heat, automatically understanding when it will switch between these modes based on building needs. This allows simulation of sophisticated thermal plant systems using a straightforward interface, without requiring coding or other complex processes.
Future role of AI within the Built Environment
As AI becomes more prevalent in our daily lives, the built environment is no exception. More and more professionals are adopting it as a collaborative tool throughout the building lifecycle - from concept and design to long-term operation and maintenance.
IES recognises the exciting opportunity that comes with integrating AI into building performance simulation, and is actively exploring how it can augment our dynamic thermal capabilities, ensuring that we continue to innovate and integrate new technical enhancements, such as the following, into IESVE:
Parallel Simulation – Significantly reduces runtime for complex analyses and can be used to counter the increased simulation speeds offered by cloud-based simulations.
Python Scripting API – Empowers users to customise, automate, and tailor IESVE functionality to their workflows e.g. harvest data and create bespoke reports. Users can use the built-in VE Script Python Editor or pre prepared scripts to automate workflows.
IES is fully committed to applying our deep expertise in building physics to the exciting opportunities presented by Artificial Intelligence (AI). We are actively exploring how AI can augment the proven reliability of the APACHE engine by improving usability and accessibility, simplifying model setup, and facilitating reporting and the automation of manual tasks. So, watch this space.
The Path Towards Smarter, More Sustainable Building Outcomes
The new features in IESVE 2025 Feature Pack 1 represent exciting technological advancements in thermal modeling, HVAC simulation and energy analysis. Ongoing development, led by IES’ product innovation team, ensures we will continue to develop our APACHE simulation engine, maintaining the proven reliability of IES’s physics-based platform well into the future.
By continually investing in and strengthening the APACHE engine, IES ensures all users with a valid license have the future-ready workflows needed to deliver truly sustainable, high-performing and cost-effective buildings.
Upgrade to IESVE 2025 and discover the power of APACHE's enhanced features.
