Question-and-Answer Resource for the Building Energy Modeling Community
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About Unmet Hours

Unmet Hours is a question-and-answer (Q+A) website for building energy modelers.

It’s simple. You ask a question. Other modelers answer it. The best answer gets voted to the top.

Or search on your topic and you might just find that your question has already been asked and answered.

And give back to the community (while showing off your expertise and earning good Karma) by helping other modelers with their questions.

Need more details? Check out the Help page.

What Does “Unmet Hours” Mean?

“Unmet hours” is common terminology in building energy modeling for the time periods (“hours”) when the HVAC systems in a building or room are unable to meet and maintain the thermostat setpoint for heating or cooling. The result is that the room gets too cold or too hot. A large number of unmet hours during a simulation is usually an indication of errors in the model.

Most modelers are all-too-familiar with the problem of unmet hours. No matter what simulation software you are using, it can be a tough problem to debug and solve. Unmet hours are a great reason to go looking for some help.

“Unmet hours” also has a double meaning that hints at the wasted hours a modeler spends trying to debug errors and look for answers–in other words, unsatisfied efforts to solve a problem.

Credit for coming up with the name Unmet Hours goes to Damien Tavan.


Area 51

The idea for a Q+A site for building energy modeling began with a proposal initiated by Neal Kruis on the Stack Exchange Network–home of the immensely popular Q+A site for programmers, Stack Overflow. Proposals are sprouted and nurtured on a special Stack Exchange website called Area 51. Eventually, if the process is successful, the proposed Q+A site wins a position under the Stack Exchange umbrella.

In December 2012 Neal Kruis initiated the proposal site on Area 51 with the working name “Building Performance Simulation & Analysis”. The site gained early support from vocal champions, Clayton Miller and Jamie Bull, who wrote about it on their respective blogs. Within the first six months, the proposal site garnered significant interest and enthusiasm from the modeling community. The site was actively promoted by Big Ladder Software and other advocates, including the US Department of Energy and IBPSA World which covered the proposal in detail in its April 2013 newsletter. At its peak the site had 245 followers.

Unfortunately, despite broad support, the proposal site lost momentum after about a year and was unable to meet the rather burdensome requirements of Area 51. The site itself has now been deleted by Area 51…which was a shame because it had many excellent sample questions.

An Independent Q+A Site

With the Area 51 proposal beginning to run out of steam in January 2014, we considered other ways to accomplish our goal of creating a Q+A site for building energy modeling. Happily, we found several open-source alternatives to the Stack Exchange platform. Developing our own independent Q+A site would allow us to skip the tedious proposal process and have complete freedom to build the best site to suit the needs of the community.

With a plan in mind, we found a willing sponsor and collaborator in IBPSA-USA to help us make it happen. Now with Unmet Hours we finally have a Q+A site for the building energy modeling community, built by the community.


Unmet Hours was originally developed with the generous support and collaboration of the founding sponsor, the USA affiliate of the International Building Performance Simulation Association (IBPSA-USA). This project was developed based upon funding from the Alliance for Sustainable Energy, LLC, the manager and operator of the National Renewable Energy Laboratory for the US Department of Energy.

We also acknowledge the support and contributions of the users of Unmet Hours and the entire building energy modeling community. Users like you are the reason that this project is successful.