The Ins & Outs of Energy Modeling

It should come as no surprise that energy efficiency has been a hot topic in the AEC industry for years. With the buildings sector accounting for about 76% of electricity use, as well as 40% of all U.S. primary energy use, reducing energy consumption and creating highly efficient buildings is a top priority. There are many factors that can improve and optimize the energy efficiency of a building—but if you’re not an engineer or an architect, you likely don’t have visibility into those decisions.

One of the ways we calculate the energy usage of a building at SHP is through energy modeling, a process that uses data and software to determine a building’s predicted energy consumption. We sat down with Jacob Faiola, Director of Engineering at SHP, to discuss the process and how energy modeling can help building owners increase energy efficiency.

First things first: How would you define “energy modeling” to someone who isn’t an engineer?

In simple terms, energy modeling is a type of computer modeling that seeks to estimate how much energy a building is going to consume. Using industry-standard inputs and software, we can compare designs to find an option that uses less energy while meeting the needs and budget of our client.

Talk to us about what goes into the process of energy modeling.

It’s easiest to describe it in a step-by-step process because that’s how most energy modeling software is set up.

  1. WEATHER: We pick a location. A building’s energy usage will be largely dependent on its location and how hot or cold it gets there; heating, ventilation, and air-conditioning (HVAC) often comprise the largest category of energy consumption in non-residential buildings. If we were building a school here in Cincinnati, we would enter that location into the software and upload a TMY file containing weather data that represents the “typical meteorological year.”
  2. ENVELOPE: We define the building characteristics. At SHP, we look at the “building envelope,” which refers to the elements of the building that encounter the “outside air”—exterior walls, windows, doors, and the roof, for instance. We will also include the size of the building, the size of the individual rooms, and the performance of the materials we’re using.
  3. INTERNAL LOADS: This is when we enter information about the “internal load” of a building—the features in a building that generate heat. Internal loads include the building occupants, lighting, and equipment like kitchen appliances and computers.
  4. SYSTEMS: We’ll define the HVAC systems. We usually have five to six typical systems that we recommend for our projects, but there are dozens of options out there—and many considerations we have to keep in mind. What are the priorities of the building owner? Who will be conducting maintenance? How efficient do the fans, boilers and chillers need to be? All those distinct factors need to be defined to get an accurate calculation.
  5. SCHEDULES: To get an accurate picture of energy consumption, we need to know the schedule of operation for the building, including when people come in, how long they’re in the building, what rooms they are using, and so on. How a building is used can change the potential energy consumption (a large high school is going to be used differently than a smaller office space, for instance).
  6. FINANCIALS: This is where we’ll define our utility rates. How much will energy providers charge the client for the electricity and gas that power the building?
  7. CALCULATE: The software processes the data and generates reports on this building’s potential energy consumption. From there, we can make tweaks to things like the HVAC system or building materials to get the energy consumption to where it needs to be for our specific client.

How does this process help your clients?

It can help in several ways—from deciding on what equipment you need to estimate when you’ll break even on your investment. The simplest version of this process is what we call “load calc,” where we determine what equipment is needed to cool or heat the space on the hottest or coldest day of the year. If the client isn’t extremely concerned about cost or energy consumption, we can just stop there.

Energy modeling happens when we add in the schedule of operation—when people are using the building. That information, along with the utility data, allows us to calculate the total energy consumption over the entire year. Then, we can go a step beyond that and start calculating the life cycle cost analysis. To do that, we add the initial cost information—how much they spent on the building or installing the HVAC. An accurate lifecycle cost analysis can help the owner determine what the payback period will be on their investment for higher efficiency systems.

Have there been instances of energy modeling changing the design of the building?

Yes—picking a different HVAC system is common, for instance. But other smaller changes can occur based on energy modeling. We convinced one of our clients to use a different glass on the façade of a new college; the initial design looked great, but it was a massive heat load on the HVAC system because of how much sun it let into the building. The SHP team recommended that they use dynamic glass that gets darker when it’s sunny out, almost like transitional sunglasses. Making that change went a long way to lowering the heat load.

What conversations happen with clients after you’ve conducted energy modeling?

Often, we’ll discuss the pros and cons of investing in energy-efficient equipment.  It’s true that some of those systems will cost more on day one, but the lifecycle cost performance is so much better. Our client Northwest Local Schools, for example, decided to invest in a chilled beam HVAC system, which costs a couple of dollars more per square foot to install but can be 10-18% more energy efficient than a traditional HVAC system. Using energy modeling we predicted that eight or nine years into the building’s life they would pay off their initial investment and start making financial returns. Seeing those results is rewarding.