Robert Fassbender's blog

What is the Best Energy Modeling Software

Posted on: May 14, 2015

What is the best energy modeling software?

If you are asking this question, you are probably either really new to energy modeling or really experienced.

Unfortunately, nobody really has the answer to this flawed question. The problem is that best can mean a number of things. Some might think that it means, "The most powerful, flexible, modern software package". But if it takes 5 years to learn how to use it, would it still be the best?

Many would argue that EnergyPlus is the best energy modeling software package. I will say with certainty that, on it's own, EnergyPlus is not the best software package.

Why isn't EnergyPlus the best software package?

EnergyPlus is not a software package at all. It is an engine. It's like saying, "The Ford Ecoboost V6 is the best car in the world" (wait, EnergyPlus is U.S. government funded, so I suppose a GM engine would be a more appropriate analogy, but I use the Ford Ecoboost analogy because I sincerely don't want to insult EnergyPlus).

See, EnergyPlus is an awesome, powerful, flexible (albeit relatively hard to learn) engine. When combined into a package (Engine+Graphical User interface), it is on the list of top contenders.

So what is the best whole building energy modeling software package?

To discuss the best whole building energy modeling software, we should consider: ASHRAE Std 140 approval, power, flexibility, feature-rich, learning curve, existing audience, reports, customization, and maybe a few more things. You might care about cost too. The only free software on the list is eQUEST.

That narrows the discussion of best software down to a few software packages:

Calibrating Energy Models

Posted on: May 5, 2015

The increasing popularity of building energy modeling (BEM) yields growing awareness of BEM to a variety of professionals. With exposure to larger audiences of various technical nature, energy modeling remains under increasing scrutiny. This scrutiny extends to all energy models, including yours.

Critics, all too often, cite discrepancies between a given BEM's projected energy cost and the reported cost of the existing building.Thus, the perceived validity of the energy-model is tied to its accuracy relative to actual utility bill data. This accuracy is most easily determined in existing building energy retrofits, where one can easily cross-reference existing utility bills with the energy model’s results.

The industry, the client, and the building simulator benefit when a model is properly calibrated with the building’s existing utility data. Given the thousands of inputs available in an energy model, building simulators often struggle with calibration of the energy-model, which illustrates the need for a systematic approach to calibrate the energy model.

User Expressions in eQUEST

Posted on: April 29, 2015

We are going to delve into “User Expressions”. This is a topic that scares many an eQUEST user, so let me be clear, you can very easily complete an eQUEST model without “User Expressions”. They are optional, but they can be very helpful.

What is a User Expression in eQUEST?

A User Expression, also called a User Input Expression, is an input that is dependent on another input. This is very powerful because it allows interdependence of inputs, and allows dynamic modeling. To really explain a user expression, let’s start out with a simple example.

Example 1:

Let’s say we wish to place one window on each wall in our simulation. It’s common that a band of glass will be based on the length of the wall. Let’s say that for most walls, we want a 5 foot band of glass, starting 3 feet off the ground that starts and stops 1 foot from each end of the wall. 

Since a window is a child of a wall, eQUEST can create the window based on known wall data. To do this, set up your window like this:

Then right click the field for width and select Edit/View User Expression:

Then Enter: #p("WIDTH")-2

How to get LEEDonline to work on a 64 bit computer

Posted on: June 11, 2014

So, you want to use LEEDonline?

First thing, you must have Internet Explorer or Safari. It won't work in any other browser. 

There's a list of other things but if you have used LEEDonline in the past, you will need to make some changes.

If you have 64 bit Internet Explorer, you will need to setup a 32 bit option. This is easy enough:

  1. Go to your desktop
  2. Right click and create a shortcut
  3. Set the shortcut path to C:\Program Files (x86)\Internet Explorer\iexplore.exe
  4. Give the shortcut a name (something like "32 bit IE" or whatever helps you remember)

Now, to make sure that this 32-bit version of Internet explorer operates in "compatibility mode":

  1. Open the 32 bit version of IE.
  2. Go to
  3. Go to the tools menu (if you don't see it, click the "alt" button)
  4. Then select "Compatibility View settings"
  5. It should have listed next to the add button, if so click the add button, and you should see this screen.LEEDv4 Compatibility Mode internet explorer

And, assuming you have the correct version of Adobe and the correct plugin, you should at least be able to log in.

Good luck and please post any questions in the comments! 

An Honest Discussion of the Design Process and BIM

Posted on: December 17, 2013

Here’s an interesting conversation we had with someone on our recently. Of course, it does not reflect the views of, but it does reflect the views of many engineers we've talked to about the design process and architects.

Anonymous: Hey - are you going to offer a Revit MEP training?

Support:  We would like to, but need to define the scope - perhaps you could help? Do you have any ideas on what a typical MEP engineer would want to learn to do in Revit MEP?

Anonymous: With regard to Energy Modeling or in BIM modeling?

Support: Considering we are an energy modeling website, let’s say energy-modeling, but I suppose BIM should tie into that as well.

Anonymous:  Well first thing I have to say is It’s an integrated design process in a virtual world….shit in yields shit out. Seriously, each discipline is at the bottom of the pyramid equally, so the basis of reaching the peak (LEED Plaque) is supported at the base of the design process by everyone. I’ve seen architects build crappy models to which there is 2,000+ walls in a corridor.

The basic Revit information needed for modeling starts with the Architects and how they build their rooms and components. Exterior wall banding (different color brick or materials used) breaks up walls into several different walls per room. Ideally, they should enter a single wall with an overal U-value for each wall type, but also be educated on how to do this through ASHRAE 90.1 for wall assembly U-values and also include lifetime degradation of insulating U-value (it’s a lot to ask)

The worst offenses I’ve seen is in the window assemblies.

Modeling a sustainable world... Lynn Bellenger remembered

Posted on: October 24, 2011


As you may know already, but if you haven't heard - I am sad to announce that Lynn Bellenger passed away Oct. 19.

Everyone in this business should really be thankful for Lynn's contributions. As ASHRAE president, her motto was "modeling a sustainable world" and pushed the relevance of BIM and energy modeling. As the first female president in 116 years, her contribution to ASHRAE itself was a breath of fresh air. In my opinion, she did more for ASHRAE than anyone in recent years.

I had only met Lynn once, but I spoke with her on the phone many times and she was always very pleasant and kind. Actually, one of my first weeks at Trane CDS, I ended up on a support phone call with Lynn. I had no idea who she was, but I simply remember asking her to "let me get some help" (to which she was very kind).

I then went and asked Clair Jacobson (who has also sadly passed away several months ago) for some help. 

Clair asked "who is it?" 
I told him "Lynn Bellenger.." and he said with a grin, "Yeah, I better take that one" 

How to Avoid Getting Ripped Off on a LEED Energy-Model

Posted on: October 23, 2011

Can you imagine hiring a Swahili translator without knowing the first thing about Swahili? What if a fake translator claimed to be an expert and even spoke a few words of Swahili to convince you of his expertise? How would you know he was lying? Likely, you wouldn't. And by the time you found out he was lying, you're being eaten by cannibals in the Congo (and no, your contract is not going to protect you!). If only you had taken a course on Swahili, you would've easily recognized the fraud and wouldn't be in this mess.

Energy-modeling is the same way. A lot of people claim to be experts, but only speak enough of the lingo to get the contract, and then slap something together and claim that it's valid (I've supported hundreds of people who have done this - I even found out they copied/pasted my emails and sent them straight to their client - just to make themselves look smart!). But how can you spot a fraud if you don't know the lingo? The best way to spot a fraud is to speak the lingo. In energy-modeling terms, that means get acquainted with the software. Maybe you won't become an expert, but you will be able to recognize one!

You might not get eaten by cannibals, but you can avoid a room full of angry Owners, investors, and architects - which might be worse than cannibals.

Recommended Courses:

Counter-Intuitive Wall Insulation Energy Study

Posted on: October 7, 2011

A while ago, published a blog, "Is insulation the best energy saver?" and illustrated the number of hours where high R-values may increase energy. People may argue, "that's what an economizer is for!"  In my opinion, that of course is a good argument, but I have talked to too many people who have asked, "Why does my energy go up with increased wall insulation?"

To test this scenario, we looked to our good friend eQUEST. We built a simple building and tested it over a range of climate zones, and a range of R-values. In order to "normalize" the data, we compared everything to R-9 insulation (which is a pretty low R-value). We also made a number of assumptions:

The Real Effect of Lighting on Energy and LEED points

Posted on: August 16, 2011

EAc1 LEED points can't fall entirely on the back of the MEP!

I've probably seen as many LEED files as most LEED reviewers. What blows my mind is that most of the files I have seen save very little in lighting, even though lighting is often 25% of the building energy costs. In my opinion, this is a result of Architects and firms who, let's face it, are too set in their ways to change their designs. (Either that, or it's just plain laziness).  Perhaps, I am being harsh and they simply don’t understand the huge impact lighting has on LEED points. So, I’m going to spell it out mathematically, but first let’s see how a typical conversation goes:

"We have a design that is going to save 30% on energy costs annually. The HVAC has an improvement of 35% over the 90.1-2007 baseline, and we are using such and such.."

…..But then, I look at the lighting and see that it is designed at 1.2 watts/sq ft compared to a baseline building at 1.3 w/sq ft .

Now if you're asking, "what's wrong with this?"-  I want to ask you, "What's wrong with you and why are you reading my blog?" Okay, maybe I'm being harsh again but it's really simple math and I shouldn't need to explain it in depth. The truth is that lights are one of the best ways to earn LEED points.

Here's a rule of thumb for LEED buildings:

 Whatever your intended net savings on LEED is, your lighting design should save that percentage against the whole building method. (for buildings where lights are the typical 15-25% of savings)

The TRUE Greenest, LEEDest state in the U.S.A?

Posted on: August 15, 2011

So, what is the GREENEST state in the U.S.A.?

This is pretty hard to gauge of course, but let's say we will use LEED buildings as a metric. If you look at the LEED buildings by state map we recently published, it's clear that California takes the cake in all categories, with thousands more LEED certified buildings than any other state. However, looking at the map, it was notable that the top 4 states were identical to the top 4 states in automobile emissions, as well as urban sprawl, among a number of other factors. 

Furthermore, when sorting the data from Certified to Platinum, some interesting trends appear. Most notably, California definitely loses its enormous advantage. So, maybe it's not entirely fair to gauge based on the number of LEED buildings, as big states with many buildings will clearly win, despite the negative environmental impact that inevitably is associated with large populations.

So, I asked myself, "what if each state was adjusted to have 10M people?"

In other words, what does it look like if we determined the data as "LEED buildings per 10M people"?

The Numbers are surprising, with the number 1 ranked building in Certified, Silver, Gold and Platinum being: