Climate change and current building energy models

Building energy modeling has been around for almost 50 years now. One of the early applications of building energy modeling was for US Department of energy by the name DOE-2 and BLAST. The energy simulation software allow to determinate with accuracy some variables that can support designers to take decisions about the best measures to apply for any building to built or already existent.

Climate change has affected different aspects of weather like temperature rise and global sea levels. All of the energy modeling software we use today use weather files or weather data to run the simulation. This weather data is very crucial to the model as it locates the model as well sets a climate and sky model for the simulation. While we argue about the accuracy of these energy models to the real building energy consumption, its accuracy today should not be the only concern.
Weather files available today are TMY weather files which represent a “Typical Year” of weather at a particular location. This is done by looking at a multiple-year history and selecting the most typical data for each month.

How are TMY files generated?

Weather stations collect hourly weather data over multiple years (up to 30 years).  To counter this effect, TMY files select the most representative year for each month, based on sunlight and temperature. The weather file is then constructed of the most representative months throughout those years. For example, you may have January from 1998 and February from 2003 because those specific data were most representative of the “typical” January and February for that location.

Fig. TMY data selection on the basis of 10 years of weather data

These TMY files are available in TMY2 and TMY3 data which represents data from 1990s and 2000s respectively.
Since all these files are used in our energy models, non of the future predictions are taken into account i.e climate change. Since we are designing building right now for next 100 years, they should be resistant to future climate, or else our current energy models are only catering to the current weather scenario. The robustness of the building should sustain in 50 years from now.

While doing an energy model, we always design systems for the worst hours of the year. Systems are designed to provide thermal comfort even in the warmest and coldest hours of the year. But we are surely not taking climate change into account, which might effect the most uncomfortable hours, rainfall, natural disasters, etc.

By doing building energy simulations in advance, it is expected that buildings can be made more climate resilient but are we really designing for the worst?