More on the Continuing Education article [Energy Modelling – Designing Buildings for Real Performance] for LEED professionals published in the Winter 2014/15 issue of SABMag.
Andrew Corney comments:
David Mead from WSP recently wrote a great article [Energy Modelling – Designing Buildings for Real Performance] in the Winter 2014/15 issue of SABMag. There is a lot to get excited about at the pointy end of performance-based design. Projects are committing to and hitting performance targets. It’s wonderful to see how far the field of performance-based design has come.
Unfortunately, predicting energy performance still takes a lot of work. This work is still too time-consuming and costly to incorporate into most projects, so there are still very few that invest in predictive analysis and post-occupancy verification. Most projects do well to run late-stage ASHRAE 90.1 calculations.
The use of simulation to help improve design needs to be broadened, and quickly. This is possible if the barriers to doing high level, informative simulation of early design concepts are broken down. Designers need access to software that guides them through the choices they need to make without asking them to make decisions relating to variables that are not well known or easy to know.
This is happening. Performance software is being made more accessible to users through more intuitive interfaces that speed up calculations through cloud processing power. Pre-populated assumptions for values that otherwise need to be guessed are also speeding up analysis for both novices and experienced users. In many cases, these assumptions make it easier to compare performance across projects in early design.
Progress in building performance is happening. Designers are increasingly empowered to make better decisions. Specialists are predicting real-world performance. What a great time to be designing buildings!
Andrew Corney is the product manager for Sefaira Systems, a cloud-based analysis tool using Energy Plus designed to help HVAC designers conduct rapid HVAC sizing and load calculations. Previously, Andrew is a PE with over 13 years of experience in high-performance design consulting and previously founded WSP’s successful Built Ecology group in San Francisco, CA.
David Mead, author of the article, replies:
In my recent article looking at delivered in-use building energy performance I noted the risks implicit in the use of concept level energy modeling tools. I’d like to take this opportunity to clarify some of the points that were made in the article relating to the undoubted benefits of such tools but also highlighting the risks of directly applying modeling output in the absence of experienced technical oversight.
The more nimble energy analysis tools, such as Sefaira, aid the design process by providing near real-time analytical feedback. This allows energy analysis to keep pace with an often rapidly evolving building design during the Concept and Schematic Design phases. However, it is important not to lose sight of the fact that the benefits of speed are gained through simplifications in input data through the use of modeling assumptions.
Building physics is extremely complex, involving multiple interdependencies between climate, building envelope, systems and occupant usage patterns. The impacts of design choices are not always intuitive and a single incorrectly applied modelling input or assumption can result in fundamentally flawed design guidance.
This last point is true of any energy analysis tool. Given that the decisions made early in the design process are often the most impactful, it is crucial that individuals understand when guidance from the software can be safely applied and when more detailed analysis techniques should be used. Precisely for this reason, it is during the early design stages that input from an experienced building physicist is most needed.
David Mead AIA, IES, LEED BD+C is an associate with WSP Built Ecology in Seattle, WA. David has been working for over 10 years on high profile sustainable building designs first as an architect and for the past five years as a high performance design consultant to architects and engineers looking to enhance their designs.