In my work as a building engineer, there is an allure to use more and more simulation, analysis, and energy modeling to optimize a building design. Some are visually enticing, with people dabbling in mass simulation and optimization like the folks at Cove Tool, others are for efficiency mandated by code with charts and tables. All use a simulated model to get a building permit.

Years ago I made a sketch of how to analytically solve the problem of rapid modeling vs detailed modeling.

It is a worthwhile teaching tool for new energy modelers and helps convey a logical workflow. However, it lacks a key piece of asking ‘why am I making this energy model in the first place?’.

I have found it is best to know why a simulated model is being built to be effective as a building consultant. Most great buildings are designed based on a series of questions when you think about it. And understanding where a team is in their decision making process is a key way to be strategic in how to pull together analytical models and presentations which are coherent and advance the conversation.

I have found four major categories design questions fall into. Each category represents the types of questions and motivations a team may have at a stage of design or for the whole project. I have found it to be very helpful to ask myself which category is my client asking for assistance? And how best can I support this effort?

1. Models built to show INSIGHT

A model can be built to just demonstrate deep insight to a topic (comfort, zero energy, micro climates) and be able to influence a captive audience with ideas, solutions, and direction. This builds confidence with analysis.

These simulated models tend to help quantify information people may know exists yet have not spent the time to pin point or condense themselves. These might be used to help to elevate everyone’s knowledge and be answers used to form the basis for larger inquiry. They can also be used to demonstrate knowledge or experience to a client about building design and performance. Types of questions may include:

  • How could a building use natural ventilation?
  • What is the energy cost savings of a Zero Energy Building?
  • What are the local weather patterns?
  • What is the energy if half the people have laptops? If they all have laptops?
  • What is the difference in energy use and costs between a design built to code, to LEED, and measured once built?
  • At what scale does a micro-grid system make sense?
  • How does radiant comfort work?
  • What are the soil conditions?
  • What is the annual rain fall?

2. Models built to TEACH

Teaching models are built to explore building energy and design relationships and opportunities. A client who may already be engaged to take the next step or goal needs analytical answers to help combine their thoughts. Analysis when teaching is typically done to start a conversation without knowing what the combined result or outcome may be. The analysis results turn into a tool for facilitated design discussion, with the purpose being to make a shared answer.

These simulated models tend to be driven by a need to teach building physics, relationships of the physical building and often how it will be used. Much of the goal in teaching simulations is to raise the bar of decision makers to be informed to make more complex decisions. Often this can be motivated by ‘current trends’ in building design, such as Net Zero Energy, or Health and Wellness. Analysis may need to be used in establishing a relationship to a location, building use, and how much energy, or the outside air quality  vs efficiency for instance. This is similar to insight modeling, though often is developed to engage a specific client or opportunity.
Types of questions may include:

  • How can the building bring fresh air into classrooms?
  • What range of comfort is possible with ceiling fans?
  • What window size opening provides how much air movement?
  • How big of a solar system will offset a building’s energy use?
  • What the energy rates and utility choices?
  • When does a façade design change the HVAC system?
  • What are the Diurnal Swings in Temperature and Humidity?
  • What are the benefits of a specific HVAC system in comfort, costs, constructibility?
  • What thickness of insulation will simplify a perimeter heating system?

3. Models built for PERFORMANCE

These models are built for optimization and are generally used to model fixes to known problems. Often the design direction is set, with the solutions understood, and the analysis helps tune each to find a specific answer.

These simulated models tend to be the most interesting technically, though are used mostly to tune an idea already agreed upon, or to find an exact answer to a problem. Often this can be seen in dealing with building diagnostics, or through determining what a buildings true energy uses are. Most energy models used in other avenues serve to demonstrate an understanding from one party to another for accuracy and specificity.

Types of questions may include:

  • How big is an HVAC system for peak conditions? Seasonal conditions?
  • What are the thermal comfort results of these glass types?
  • Will this configuration of solar panels produce enough energy?
  • What equipment change will result in saving peak power demands to avoid a utility demand charge?
  • What is the right window placement and openings for natural ventilation to be effective?
  • How many geo-thermal bore holes are needed to balance the heating and cooling loads in a year?

4. Models built to CERTIFY

This type of energy modeling is the most common and really used to obtain a title of compliance, be it code compliance for a building permit, green rating, or an incentive criteria.


These simulated models are the most popular and proliferate. This is neither good nor bad, it is just so. These models tend to be based half in reality of how a building is designed and half in a reality of typical use and standardization. The answers derived from models for certification are often niche creations and provide an estimate of a building’s relative performance against a standard or baseline. In compliance, much of the importance is verifying if a building’s performance is fair and comparable to others in the same structure. In this way, some compliance systems have not figured out how to allow for all types of architectural design and HVAC systems for ensuring fairness, though it can often feel like the opposite.

Types of questions may include:

  • What HVAC systems can I use to obtain a building permit?
  • How many LEED points is this high efficiency lighting system worth?
  • Will the interior blinds contribute to my LEED platinum target for efficiency?
  • What is the code minimum insulation thickness we can use for this building?
  • How many solar panels do we need to achieve the renewable energy credits for certification?
  • What is the most amount of glass we can use with this HVAC system choice?
  • If we install low-flow hot water fixtures, can we get more LEED points?

Knowing Why

While each of these lessons and categories serves a purpose, knowing the basis of the design and which category a question is coming from can greatly improve how a simulated model is built. Knowing is at least half the battle in this case. Being able to anticipate the right category can help to make a plan for how to answer the initial question and to thinking about what the next set of questions could be. Often times, it is best to fully understand the source of a question or discussion before starting to develop the analysis. There are many ways to build energy models and some can take 10x longer than others and still give the same level of confidence and results a team may need.

If this approach is helpful to designers working with energy modelers or energy modelers themselves, I would love to hear from you!