Just like in the aerospace industry, the building industry benefits from testing design ideas with models. With an energy model, building designers have a tool that assists in achieving energy reduction targets. There are multiple reasons for setting energy reduction targets, such as designing a net zero energy building, certifying a green building (LEED, Green Globes, etc.), complying with an energy code, stipulating energy cost savings for an energy performance contract, or calculating the return on investment for an energy audit. Once the energy reduction target has been set, energy modeling is utilized to test multiple design options to determine the ones which meet the target.
Ideally, this energy modeling analysis occurs during the beginning phases of the building design process. Patrick MacLeamy* illustrated this with what is now known as the MacLeamy Curve shown in Figure 1 below. This curve was developed to show that investing additional money in the early phases of the design has the potential to create the biggest impact since the cost of design changes increase over time.
Figure 1
Once you’ve decided to use energy modeling to achieve your energy reduction targets, you’ll need to pick a software tool. There are many tools available, varying from simple to complex and including both paid and free options. A summary of software tools that focus on testing design options are provided below:
- Includes plugins to popular 3D modeling tools (Sketchup and Autodesk REVIT)
- Simple Interface
- Easily test design options
- Quick Results
- Customizable, large scale analysis
- Calibrate models to utility data
- Parametric analysis
- Includes plugin to Sketchup
- Parametric Analysis Tool (PAT) allows easy tests of design options
- Large scale analysis in the cloud
- Free and developed by NREL
- Generic optimization software that works with multiple energy simulation tools (Energyplus, DOE2, etc.)
- Customizable
- Free and developed by LBL
If you are interested in learning more about these software programs, there are many Youtube tutorials available. For example, here’s a video tutorial of how to use GenOpt with Energyplus.
One last thing to be aware of is the current limitation to implementing this process. Some potential roadblocks to early-phase energy modeling are as follows:
- Cutting-edge technology is hard to model (such as phase-change materials, VRF systems, etc.)
- Sometimes software which targets testing design options early in the design phase is overly simplified and doesn’t include all of the design options that you want to test
- Getting 3D geometry information from BIM tools is tricky and often times transferring information between BIM and the energy modeling tools via gbXML or IFC involves pre- and/or post-processing. Unfortunately, sometimes starting from scratch is easier.
- Convincing Building Owner or Design Team to spend a little more time and money upfront to save money later can be a challenge
What are your experiences with achieving energy reduction targets with energy modeling? Please tell us on social media. Additionally, let us know if we can assist you in achieving your targets.
* Source: “Patrick MacLeamy on the Future of the Building Industry – HOK.” http://www.hok.com/thought-leadership/patrick-macleamy-on-the-future-of-the-building-industry/. Accessed 19 Jan. 2017.