23ASHRAE Seminar Recording

Seminar 11. Energy Modeling vs. Actual Building Energy Consumption: Why Do They Seem to be So Different?

2013 ASHRAE Annual Conference

Energy modeling has become a vital part of the standard design criteria of most buildings as the owner wants to know what it is going to cost to operate his building. This session looks at some of the issues and reasons why energy modeling programs and actual energy usage in buildings, in many cases, provide different results. Some of the problems are driven by the level of energy efficiency desired, stricter code requirements, efforts to reduce CO2 emissions and commitment to sustainability. The use of BIM as an integration program and tool is discussed as well as several programs that are being used. Conflicts between modeled energy usage and actual results along with suggestions and partial solutions to the problems encountered are reviewed.

  • Prediction and Verification of Energy Performance in Energy Efficient Multi-Family Dwellings (DE-13-C040)
    Hans Bagge, Ph.D., Associate Member, Dennis Johansson, Ph.D., Associate Member
    The building industry is facing a great challenge. Energy efficiency has to be significantly improved in new, as well as in existing buildings in order to reduce CO2emissions. This calls for actions from all involved in the building process, from architects and designers to construction workers and operation managers. Predictions of energy use and indoor climate generally do not agree with results from measurements in buildings during operation. These discrepancies are counter-productive to the implementation of energy-efficiency and sustainability measures. This paper presents results from a research project that addressed these issues and suggests viable partial-solutions to the problems encountered and discusses them in a building process context.
  • From Design to Occupancy: Strategies to Enhance Building Performance and Prediction Accuracy (DE-13-C041)
    Anthony Hardman, P.E., Member, Leslie Beu, Member, Tom Riead
    Under optimal circumstances, energy performance is a key driver throughout the lifecycle of a building.  In reality, the significance of energy performance rises and falls in concert with energy prices over the span of decades. Unlike previous energy cost inflation cycles, the cycle of the last decade has combined with non-monetary factors such as global warming and the adverse effects of poor air quality, to generate a firestorm of public awareness pertaining to how our buildings consume energy, and what should be done to reduce it.  As a result, energy services companies (ESCO’s) and the US Green Building Council (USGBC) have experienced an explosion in growth over that same timeframe.  Energy models of varying complexity are used by both groups, with the goal of enhancing building performance.  ESCO’s deal primarily with existing buildings while the majority of USGBC’s LEED projects fall under the New Construction rating criteria. This report draws on the expertise of professionals operating across the full spectrum of the building lifecycle.  Surprisingly, this investigation has led to the discovery of key variables to building performance that are (too) often overlooked in both the design and occupancy stages, which results in poor performance.  The good news is that many of the significant contributors to poor building performance are correctable without significant capital outlay.
  • Architecture, Cartography and Energy: Mapping the Way We Share Information to Build Better Buildings (DE-13-C039)
    Matt R. Grinberg, P.E., Member, Adam Rendek
    The building industry is seeing an increase in demand for energy analysis on projects, either as part of an energy audit or included in the design process. This demand is driven by an increased focus on energy efficiency, stricter codes, and an increase in commitment to sustainability. Specifically in California, the Public Utilities Commission has a Net Zero Energy Initiative that states that all new commercial buildings will need to be built as Net Zero by 2030 and 50% of all existing buildings need to be converted to Net Zero. The only way these targets can be achieved is if energy analysis tools will be utilized better than they are today. This study maps out the interactions between architects and engineers from the perspective of the present state of BIM and energy modeling tools. The result of the study – a workflow map – identifies pitfalls and technicalities that often derail current workflows. The iconography of the workflow map shows the level of confidence in the exchanged information, and the specific details of each information exchange. This allows practitioners to see where the workflow fails to meet modeling schedules and budgets.