By David M. Newman, P.E., C.E.M., Vice President of Engineering, Energia
This article is Part 3 in our ‘Three Pillars of Performance’ series.
If you missed Parts 1 & 2, you can catch up by reading:
In my last article, I discussed Retro-Commissioning (RCx) which is the process of investigating and fixing existing buildings to get them back to their original design intent. It’s a crucial service for correcting performance drift.
But what if we could prevent that drift from the very beginning?
That’s where Energy Modeling comes in. It’s the proactive counterpart to Retro-Commissioning. It serves as a powerful digital tool that allows us, and our AEC partners, to get the design right from the start.
It’s no longer an optional step or a checkbox to be marked off. For any major renovation, it’s a critical part of the design process that can help you make smarter, more efficient, and more confident engineering decisions.
3D Energy Modeling Example of Building Properties
Not Your Old-School Calculation
Not long ago, sizing a new boiler or chiller plant involved a series of hand calculations, manual methods or largely based decisions on the previous equipment size for retrofit projects. The result was almost always the same: oversized, inefficient systems that wasted energy and capital.
Today’s modern energy codes have made that approach obsolete. In New York for example, the Energy Conservation Construction Code of New York State (ECCCNYS), essentially says that for any major HVAC modification or renovation, you can’t rely on old-school calculations or simply match the size of the previous equipment.
Instead, you must validate your design for efficiency, which requires a detailed energy model. It’s the only way to understand the complex interactions in a large building and optimize all its systems to meet actual performance requirements.
An Energy Success Story: Modeling a Path Forward at a Long Island School District
The strategic value of energy modeling becomes clear when you’re facing a complex renovation with multiple stakeholders and competing priorities. We recently experienced this firsthand while working with a partner on a major steam-to-hot-water conversion for a Long Island New York school district. Building a digital twin of their facilities was essential.
Comparing Scenarios and Managing Client Expectations
The district, like many of our public-sector clients, had ambitious goals. They wanted to explore full electrification and geothermal energy. An energy model allowed us to analyze these scenarios with hard data.
We were able to show that full electrification would actually require significant supplemental electric heating to carry the building through deep winter, given poor heat pump performance under extreme conditions and needed perimeter heating, drastically increasing installation and operating costs. For geothermal, the model showed exactly how large the well field would need to be. When the client realized it would mean giving up their only soccer field, the conversation quickly shifted. The digital model provided the data needed to debunk unworkable options early and justify the most practical path forward.
The Central Chiller vs. VRF Decision
The model’s greatest value appeared when we analyzed different technologies for heating and cooling. A key decision was whether to use a traditional central plant chiller or a more modern Variable Refrigerant Flow (VRF) system.
A central chiller is efficient at peak loads, like a 100-degree day in the middle of summer. But that’s a very small window of its total run-time. For the majority of the hot season during the school year, the “shoulder months” of May, June, and September, the system is only running at partial capacity.
Our model allowed us to compare the two systems across an entire year of operation. It showed that while the chiller performs well at its peak, the VRF systems are much more efficient during moderate periods because they can modulate, throttle down, and supply exactly the amount of cooling at specific space needs.
We could even model using the VRF heat pumps as a highly efficient offset to the hydronic heating in milder weather, running detailed comparisons to find the outdoor temperature tipping point where the boilers should take the lead. The model transformed a complex decision into a clear, data-driven choice.
The Art and Science of an Accurate Model
An energy model is a fantastic tool, but there’s a danger that it can also give you very wrong answers if you’re not diligent. The most common mistake I see is using a model to try and justify a decision that has already been made, rather than using it to steer the design process from the outset.
“We had to chase down blueprints from 1926 to understand the original construction”
Building an accurate model is a significant undertaking that requires expertise. For the two buildings on Long Island, we probably invested 80 to 100 hours per building. We had to chase down literal blueprints from 1926 to understand the original construction: brick, then an air gap, then cinder block, then plaster or sheetrock, among other materials.
You also have to model the building as it truly exists, including its orientation, number of windows, and the different construction types of modern extensions versus the original structure. For older buildings, it’s a lot of investigation work, but this diligence is the only way to ensure the model’s outputs are reliable.
Why Partner with an Energy Modeling Specialist?”
With codes getting stricter, many AEC firms are doing energy modeling because they have to. We’ve had friendly chats with partners about what a “headache the models are,” and we get it. It’s a necessary evil for many, and it’s a newer process for some.
This is where Energia provides unique value. Because we have been laser-focused on high-efficiency systems and complex VRF designs for years, this level of detailed modeling isn’t new to us. In fact, it’s core to what we do. We have a unique expertise in comparing these advanced technologies and translating the data into a clear roadmap for our partners.
As the bar for efficiency keeps getting higher, and traditional equipment effectively becomes illegal under new codes, having a partner who has already mastered these advanced systems and the models that prove their worth is no longer a luxury; it’s a necessity.
