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The ASHRAE 209 Standard is an essential framework for integrating energy modelling throughout the design, construction, and operation of new buildings or major renovation projects. To help you make sense of it, we spoke with Mohamad Wathaifi, member of the ASHRAE Standing Standards Project Committee 209, to share key insights and advice for those looking to implement the standard in their projects.
ASHRAE 209 provides a framework for utilising building energy modelling throughout the different phases of a building's design, construction, and operation. The standard outlines 11 modelling cycles that guide the integration of energy simulations to support energy-efficient design decisions and performance assessment.
Each cycle is designed for specific project stages, from early conceptual design to post occupancy analysis, aiming to optimise energy efficiency by addressing different aspects of building performance.
Before engaging in the modelling cycles outlined in the ASHRAE 209 standard, there are important requirements to establish a strong foundation for energy modelling:
These requirements ensure that the design team is aligned on energy goals and informed by contextual factors, setting the stage for successful implementation of the modelling cycles.
ASHRAE 209 involves 11 modelling cycles, which align with the early, detailed design, construction and post-occupancy stages of any project:
Cycle 1: Simple Box Modelling
Establishes a baseline for energy use and evaluates how energy is distributed by end use across the building. At this stage, basic simulations are conducted to assess the impacts of building geometry, orientation, and envelope characteristics. The outputs include early estimates of energy consumption, peak loads, and a breakdown of energy use by end-use.
Cycle 2: Conceptual Design Modelling
Energy performance improvements relating to the building form and architecture are assessed. By comparing alternative designs, teams can understand the implications on building energy use and provide recommendations for enhancing building form to achieve the project’s energy goals.
Cycle 3: Lighting and Mechanical System
This cycle focuses on identifying strategies to reduce energy use and peak loads before selecting HVAC systems. The analysis targets load-reduction measures related to the building envelope, lighting and internal equipment, enabling teams to quantify potential load reductions and recommend further energy-saving strategies.
Cycle 4: HVAC System Selection Modelling
Assesses the energy and demand impacts of different HVAC system options. Through comparative analysis, multiple system configurations are assessed to inform optimum selections based on energy performance and costs.
Cycle 5: Design Refinement
This cycle refines the design through more detailed simulation of one or more building systems including HVAC, lighting, and the building envelope, generating detailed performance metrics to further develop and validate design choices.
Cycle 6: Design Integration and Optimisation
Building systems are optimised to meet performance and energy reduction goals by applying multi variant optimization techniques to analyse the interaction between design variables including HVAC, envelope and control systems.
Cycle 7: Responsive Design Alternative Modelling
Supports the holistic evaluation of value engineering proposals on the building’s energy performance. Trade-offs between cost and performance are analysed to help the design team make informed decisions about incorporating cost-saving measures without compromising overall energy efficiency.
Cycle 8: As-Designed Energy Performance Modelling
The final design is simulated using as-designed inputs to verify that it meets the project’s intended energy performance goals. The outputs from this cycle also include supporting documentation for compliance.
Cycle 9: Change Order Modelling
The impact of any design changes during construction are evaluated to determine their impact on energy performance. Each change order is assessed to determine how it might affect energy targets, and recommended actions are documented to mitigate any adverse effects.
Cycle 10: As-Built Energy Performance Modelling
After construction, an energy model is developed based on as-built conditions. This cycle compares actual construction outcomes with as-designed performance expectations and benchmarks. The goal is to confirm energy performance compliance and identify any discrepancies introduced during construction.
Cycle 11: Post-Occupancy Energy Performance Comparison
The final cycle compares actual energy use with modelled performance after one year of operation. Using measured data and weather-adjusted simulations, this analysis helps to identify and address operational inefficiencies during the post-occupancy stage, while also providing insights to improve future modelling efforts.
Following ASHRAE 209 provides a systematic approach to integrating energy modelling throughout the design, construction, and operation phases of a building. By adhering to this standard, building professionals can:
One of the key objectives of ASHRAE Standard 209 is utilising energy modelling as a design assistance tool. This broadens the benefits of energy modelling beyond the conventional use in documenting how requirements of codes or green building rating systems are met. This profoundly increases the value of energy modelling in projects and elevates the role of the energy modellers to active participants with project teams.
The early energy modelling cycles described in the standard bring energy modelling to projects sooner than the usual practice does. Early insights from conceptual models inform design teams when it is relatively easy to make changes to architectural design and select the best performing HVAC design concepts.
Energy simulation tools that serve the standard objectives best are ones that can address the challenges of decision making in real life projects. The ability to handle detailed HVAC system simulation, for example, brings the credibility needed to the results for them to be considered in serious technology selection and design concept decisions.
Post-occupancy modelling doesn’t only help identify energy saving measures, but also informs energy modelling of future projects. Operators and occupants constantly make changes that effect systems operation. Successful post-occupancy models are ones that make effective use of energy metering and building automation systems for calibrating models with actual operational data.
The industry is expanding beyond energy modelling to capture the broader aspects of building performance modelling. This is how indoor environmental quality metrics can be addressed, and operational carbon emissions can be modelled. The impact of future changes to the climate can also be assessed.
My advice to professionals new to ASHRAE Standard 209 is to assume an active role on project teams. Ensuring at all times that their models analyse practical design options and provide the timely assistance the project needs in making design decisions at the times these decisions are being made, not after.
Interested to learn more about how you can integrate ASHRAE Standard 209 into your projects? Get in touch with our expert consulting team to see how IES can support.
