Credit: Henry Obasi

In 2010, Martha Johnson, administrator of the General Services Administration (GSA), announced the GSA’s bold commitment to achieving a zero environmental footprint. This commitment, plus carbon neutrality initiatives set by Architecture 2030, the AIA, and other institutions, will require innovative design approaches, supported by forward-looking building simulation and energy codes in the United States.

Energy codes have become progressively stricter over the past decade, spurred by the green-building movement, the government, and climate-change research. One major concern is the lack of uniform code adoption across the United States. While 20 states currently reference the latest version of the International Energy Conservation Code (IECC 2009) and ASHRAE Standard 90.1-2007 for commercial buildings, seven states have no statewide energy code, and the rest reference the 2006 or 2003 IECC, or a state-created code. Energy codes prescribe minimum requirements for a building’s envelope, lighting, hot water used for non-heating purposes, HVAC, and power systems, using mandatory, prescriptive, and performance-based compliance paths. By 2013, 32 states are expected to meet or exceed the 2009 IECC or 90.1-2007, which is a move in the right direction. (See a state-by-state listing of current energy codes at

Performance-based compliance has been brought into the national spotlight, spurred in large part by Energy and Atmosphere Credit 1 (Optimize Energy Performance) in the USGBC’s LEED rating system. Because of this credit, the notion of exceeding energy code by a certain percentage has become commonplace in the industry. Similar to how we rate a car’s fuel economy, there is a desire to quantify a building’s performance with one number.

Homing in on percentage savings requires whole-building energy modeling, most often using the performance-rating method (Appendix G) of ASHRAE Standard 90.1. Modeling to this method is fraught with challenges, and significant variability in results often occurs because of differences in the software tools used, an energy modeler’s background, hundreds of input assumptions, and interpretation of standards language.

One major challenge is that ASHRAE Standard 90.1 is managed as a continuous maintenance standard, which allows addenda to be proposed and adopted continuously. The 2007 standard has more than 100 addenda—some of them significant—and it raises the question: How do owners, designers, builders, and code officials keep up? Due to a significant focus on LEED and the intricacies of Appendix G modeling, mandatory and prescriptive approaches are missed or potentially misapplied. In 2010, the Institute for Market Transformation completed a study that showed that $810 million in funding would be needed to achieve 90-percent energy-code compliance, resulting in a six-to-one benefit-cost ratio in energy cost savings. Has energy-code compliance and modeling become too complicated, heading in the direction of the nation’s tax codes?

In engineering schools across the country, students are taught the concept of KISS: Keep It Simple, Stupid. Energy modeling has become an important part of a building’s design process, but can result in a disproportionate amount of time spent on baseline model creation, rather than parametric design optimization. With carbon neutrality as an aspiration, the baseline becomes less important than what a project team within a budget can do to achieve best value, a balance between energy efficiency and indoor environmental quality. The recently opened research-support facility at the National Renewable Energy Lab in Golden, Colo., is a good example of a net-zero-energy LEED Platinum project that achieved aggressive goals within a tight budget, using simulation appropriately. By using the daylight simulation tool Radiance in the conceptual design phase, the team was able to easily make changes to glazing selections and the building form to optimize daylighting. The team was able to determine the optimal angle for the top floor’s sloped ceiling and shape custom-designed window louvers to better direct daylight inside.

Owners and design teams must be careful to have an open dialogue about the impact of input assumptions on simulation results. No energy model can pinpoint actual performance because of the difficulty in accounting for climate variations, building maintenance, occupant behavior, and operations. For example, in a given year, solar radiation on a project site may vary by up to 10 percent from the median.

In 2009, ASHRAE announced the Building Energy Quotient labeling system with the goal of providing publicly visible labels showing the energy performance of a building as designed and in operation via a grade-based system. Adoption of this labeling system will increase transparency, but it must also be deployed with standardized software tools to ensure consistency.

As the building industry continues to struggle in this difficult economy, energy efficiency must be achieved through clear standards that can be consistently and easily enforced so that time and money is not wasted. Energy codes can help stimulate demand for robust and efficient building products. Can the industry rally together to adopt a national energy code? By standardizing codes, the playing field will be leveled and will allow for greater synergy across the United States with improved education and enforcement capability. Let’s unify energy code and simulation efforts so we can all do more with less.

Roger Chang, Assoc. AIA, is principal and director of sustainability at Westlake Reed Leskosky.