Understanding Post-Occupancy Goals to Establish Baseline Energy Modeling
What is the connection between building occupant satisfaction and sustainability? What are some examples of sustainable design strategies that lead to higher occupant satisfaction and also contribute to resource savings?
Building occupant satisfaction can be quantified. An analysis of monthly or yearly energy usage in previous buildings illustrates how the occupants of that particular program preferred to use their space. Understanding what building occupant satisfaction means by analyzing existing buildings is a step towards sustainability in designing new Projects. This is why this Publication emphasizes designing accurate energy models by studying existing buildings and understanding the Owner’s vision for intended use and operating schedules. An example of this is using occupancy sensors for artificial lighting and HVAC. Let these systems cater to the needs of the occupants, but not surpass the needs of the occupants. Oftentimes, buildings are being artificially lit and conditioned in unnecessary quantities or unneeded times. The more sustainable method is to respond to occupant needs.
Another method is to first understand what building occupant satisfaction means for that particular program/climate and then analyze all the available systems that can cater to the occupant’s needs. Required/desired lighting and temperature can be regulated passively, more sustainably, before mechanical systems are used as supplemental methods. This results in the space functioning to occupants satisfaction in the most sustainable means possible.
Why are benchmarks/targets critical for analyzing actual building performance data?
Early in the design process, the established energy consumption benchmarks/targets drive the overall building design. How the benchmarks/targets are calculated, however, can lead to a highly efficient building or a building that is over designed for its intended use. According to the publication, titled Hitting the Whole Target: Setting and Achieving Goals for Deep Efficiency Buildings, there are two basic enhancements to the prediction methods in modeling building performance that will result in a more accurate representation of actual building performance:
- “The analysis must give full consideration to all energy-using systems, not just those currently regulated by codes and standards. Increased attention to plug loads is the key step for an all system or ‘all-in’ analysis.
- “Modeling should attempt to accurately predict actual measured performance. This requires universally establishing this expectation, and an assessment of anticipated operating conditions by the design team working in conjunction with the Owner. Use of actual anticipated operating schedules is the key difference from many applications of modeling for code or rating system compliance.” Oftentimes, using information from existing similar buildings is a useful component in establishing a believable benchmark.
Once an accurate benchmark/target is established, the design can be tailored to achieve this target. This benchmark/target is also critical for post-occupancy analysis. If the building is operating at a rate that is drastically different than the original benchmark/target, then closer inspection is required on all systems to understand what needs to be further calibrated.
- “The analysis must give full consideration to all energy-using systems, not just those currently regulated by codes and standards. Increased attention to plug loads is the key step for an all system or ‘all-in’ analysis.
- “Modeling should attempt to accurately predict actual measured performance. This requires universally establishing this expectation, and an assessment of anticipated operating conditions by the design team working in conjunction with the Owner. Use of actual anticipated operating schedules is the key difference from many applications of modeling for code or rating system compliance.” Oftentimes, using information from existing similar buildings is a useful component in establishing a believable benchmark.
Once an accurate benchmark/target is established, the design can be tailored to achieve this target. This benchmark/target is also critical for post-occupancy analysis. If the building is operating at a rate that is drastically different than the original benchmark/target, then closer inspection is required on all systems to understand what needs to be further calibrated.
What are some of the limitations of traditional energy models when it comes to predicting actual building performance?
The referenced Publication identifies two fundamental limitations to the traditional approach of energy modeling:- “Codes and standards only address a fraction of the energy-using systems in the building.” This means that relying on codes and standards to establish a reliable energy usage benchmark will leave major gaps in the design.
- “The models are only as good as the assumptions about operating conditions and building management practices.” Many traditional energy models are created without conducting interviews with the Owner in regards to occupancy schedules, intended plug load capacities per program, weather, occupancy comfort levels or future growth. Traditional energy models rely on “operating assumptions and equipment not customized to the building.”
Oftentimes, the conventional planning method for the Project’s energy infrastructure is to design an energy plant capable of serving the building based on its peak loads. “Typical practice is to use rules of thumb or repeat past practice, without feedback from measured performance of the past projects. This can result in excessive margins of safety and misallocation of project resources toward larger plant systems.” The project ends up consuming much more energy than it really needs to function successfully.
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