The debate continues as to whether to favour predictive energy modelling during design or whether to rely on actual building performance monitoring during use.

One of the sustainable design debates being heard these days is how to resolve the gap between green building modeling and actual building performance. Organizations like the US Green Building Council (USGBC) have been criticized for rewarding green building designs that don’t perform to desired expectations, causing some to doubt the efficacy of energy modeling altogether.

But the industry is responding to the criticism in more ways than one. Defending its work, the USGBC recently released an Energy Performance in the LEED Rating System report to demonstrate their ongoing commitment to improvement and showcase new tools for measuring actual performance (post-construction). These include:

  • LEED for Existing Buildings: Operations and Maintenance which was re-launched in 2008. It now requires whole-building energy metering and reporting via ENERGY STAR for one year minimum prior to certification. The program has been extremely popular.
  • Data disclosure means that all LEED building owners are now required to share water and energy usage data for at least five years.
  • Building Performance Partnership is a new program that encourages voluntary feedback from all LEED-certified projects for the purpose of measuring success and further fine-tuning USGBC rating systems.

The organization hopes to develop even more techniques for measuring and improving actual building performance through the next phase of LEED system development.

In addition, the Rocky Mountain Institute and USGBC  along with partners ASHRAEIBPSA-USA, and the Institute for Market Transformation, organized a two-day Building Energy Modeling Innovation Summit aimed at identifying immediately actionable opportunities and solutions in methods/processes, software tools, education/certification, market drivers, and support/resources. By all reports, the summit appears to have been a great way for many stakeholders in the industry to work together to find creative ideas that will undoubtedly influence the future of the industry.

Both Design and Operational Measurements Are Needed

When comparing design performance with operational measurements, the truth is that we cannot replace one with the other. Measurement systems like the UK’s EPCs (Energy Performance Certificates that evaluate a building’s design performance) and DECs (Display Energy Certificates that track the actual performance once buildings are built. We recently discussed them here ) are both necessary.  We need to be able to evaluate our designs during the design phase (through the likes of EPCs) to prioritise techniques and methods used to get the best results, and then use DECs to measure the results of the design during operation so that we can a) continue to improve operations where required and b) to adjust our methods of evaluating designs in the future.

The debate certainly is a productive one as it forces the green building industry at large, and the energy modeling industry in particular, to continually improve as it matures. When it comes right down to it, we need to evaluate both predicted and actual performance if we are to continue to make progress with green buildings.