The Process of Energy Modeling – Part II

By Paul Greenwalt

Wood Harbinger’s engineers have been blogging since 2013! This Throwback Thursday series features posts from back in the day that are just too good to stay at the back of the blog. Enjoy this one by Paul Greenwalt, originally published on January 9, 2014:

In Part I of this series, we focused on the general process of energy modeling and a few of the benefits it can provide a design team.  As promised, in part II of The Process of Energy Modeling we will cover the times when an energy model is an essential tool for a project and what you will need before undertaking this process.

A brief recap of the first installment:

  1. Energy modeling is a way to compare a proposed building design to a prescriptive, reference building.
  2. Modeling the proposed building determines the required baseline for an appropriate, acceptable, and useful comparison.
  3. The main uses for an energy model are:
  •  Energy Life Cycle Cost Analysis (ELCCA)
  •  Pre-construction recommendations, value engineering, energy cost savings, increased building efficiency, etc.
  •  LEED, Green Globes, Living Building Challenge, or any green building, energy savings program.

An energy model is a very powerful tool that can reveal holes in a design, or provide insightful ways to improve the design without stressing a budget.  To determine if an energy model would be beneficial, there are a few major factors that should be taken into consideration.

The flow chart below is a very basic way to check with your owner and design team to determine whether an energy model should be applied.  Of course, if a model can be created, I would always recommend doing so.  Not only is it a way to thoroughly analyze the project design, but it can provide benefits down the road long after the building has been built and commissioned.

But there is one essential question that needs to be addressed first, “Will this project be attempting LEED or any other green building protocol?”  This will immediately indicate whether an energy model is necessary.  If the answer is, “No,” then the flow chart, along with many other project specific questions, will determine the need for an energy model.

Other determining factors may include:

  • Owner requested the energy model
  • Your firm wants to prove its sustainable promises – high efficiency HVAC, improved envelope, and/or reduced lighting power densities.
  • Already building a load calculation model? An energy model is right around the corner and with a little added cost, the owner could see that cost return in energy savings!

So, you have decided to create an energy model

Now that you and the design team have established the need for an energy model, make sure to collect the details. There is a great deal of basic information that goes into your model that you need to accurately represent. Whether it is the owner, architect, or contractor who holds this information, the proposed building as well as the existing or baseline building needs to be taken into account.  Here is my quick reference checklist for the critical information necessary to build a complete energy model:

What tools are necessary for an energy model?

There are many great tools out there to help develop and produce an energy model.  Your client may have a preference, but ultimately the choice is up to you because learning a new program can be time consuming and can add to the time it takes to develop the actual model.

Two programs have been created by large HVAC equipment manufacturers.  Trane’s program is called TRACE700 and Carrier’s is HAP, which stands for Hourly Analysis Program.  Both programs are fairly user friendly once the engineer is familiar with the layout and organization of the interface, however training is recommended.  Carrier’s HAP is just slightly limited by comparison due to a reduced number of systems allowed and a few other minor restraints, but most modelers would agree that you would be hard pressed to max out the ability of this particular program.  Where Trace wins it is in the tech support.  Trace has an extensive support system, starting with the Help menus and User Manual and finishing with the team of experts that can help guide you to your project solutions.

There are several energy modeling programs available from independent developers, sometimes free of cost.  Some of the most widely used programs include eQuest, EnergyPro, and EnergyPlus.  These programs offer fast computations, user friendly interfaces, and accurate calculations.  The drawbacks of using free software can be lack of support, infrequent updates, or inherent software limitations.

One program that has recently entered into the energy modeling realm is Revit from AutoDesk.  This Building Information Modeling (BIM) tool has quickly evolved to become one of the most widely used in the industry.  Its offering has increased from 3D building modeling to include collision detection (ability to analyze and detect conflicts between mechanical, electrical, and plumbing objects with architectural and structural elements), embedded equipment information and material types, load calculations, and energy modeling.

I have used Trane’s Trace700 for the majority of my Energy Models and ELCCAs.  The program recently added many key features like a LEED Guide and ASHRAE 90.1 Baseline alternative builder.  The main downside to this program is the notoriously slow calculation time.  Depending on the size and extent of your model it can take several hours to run a simulation.  The major benefit to this program as a whole is the level of customer support.  This is no outsourced, “have you tried pressing the power button” type of one trick pony.  Each one of the techs has been in your shoes.  They will do everything to help resolve whatever issue you have.

No matter what program you use, the important thing to keep in mind is that energy modeling is a time consuming and intricate process that has many implications from energy and cost savings to LEED or Green Globes certification.  The next part in this 3-part series will focus on a few tips and hidden benefits of Energy Modeling that will make you look like a genius and help save your clients’ money!

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