Building Efficiency Modeling Shows Targets May Be too High
NAIOP, the Commercial Real Estate Development Association, released on Feb. 24 a report that demonstrates the levels of energy efficiency that standard office buildings can reach while remaining economically feasible.
The study was initiated to determine if commercial development could achieve reduction targets of 30-50 percent above the ASHRAE 90.1-2004 standard – the benchmark often cited in legislation and other calls for mandatory reductions.
Using a recently completed four-story, 95,000 square-foot, Class A office building as the prototype, the research modeled the prototype in three climate zones represented by Chicago, Ill.; Baltimore, Md.; and Newport Beach, Calif.
Findings show that although significant energy efficiencies can be achieved (varying by climate zone), reaching a 30 percent reduction above the ASHRAE standard is not feasible using common design approaches and would exceed a 10-year payback. The study concluded that achieving a 50 percent reduction above the standard is not currently reachable.
"The study provides an unbiased insight into the energy targets practical to commercial development today," said Thomas J. Bisacquino, NAIOP president. "Identifying an energy reduction level that is both environmentally responsible and equitable to the developer is essential in protecting the prosperity of commercial real estate."
The study was conducted by ConSol, a California-based independent energy-modeling firm, using the Department of Energy's EnergyPlus v2.2, a building energy simulation program for modeling building energy uses.
Modeling included enhanced wall and roof insulations; varying levels of exterior glazing; higher-efficiency window assemblies; reduced air infiltration via the installation of an air barrier; reduced lighting power densities; higher-efficiency HVAC equipment; and photovoltaic electricity energy generation.
Using technologies and methods to increase effectiveness, the maximum efficiency reached was 23 percent in the Chicago model. Results across the climate zones vary by more than 7 percent, given baseline energy uses in domestic water heating; lighting; heat generation; air conditioning; and fans, dampers and HVAC equipment.
Overall, energy savings, cost increases and payback periods are:
- Chicago: 23 percent in energy savings; $188,523.45 cost increase; 8.8 year payback;
- Baltimore: 21.5 percent in energy savings; $165,148.13 cost increase; 11 year payback;
- Newport Beach: 15.8 percent in energy savings; $169.898.13 cost increase; 12.2 year payback.
"With the results of achieving higher efficiency targets differing so greatly across the climate zones, the study reveals that a 'one-size-fits-all' approach to mandatory energy reductions does not work in legislation or other mandates," said Bisacquino. "It is important that policymakers and others realize the economic consequences that imposing mandated targets will have on the development industry."
Study results show that employing solar generation technologies could close the gap between the efficiencies achieved in the study and the 30 percent above the ASHRAE 90.1 -2004 standard. However, at an installed cost of more than $1 million and a payback of up to 100 years, it far exceeds practical and economical limits.
Additionally, elements of a holistic, integrated design approach that could yield higher energy efficiencies were identified as impractical in the study's building prototype, which represents more than 50 percent of total new Class A commercial construction. For example, in the Newport Beach model, a geothermal system (a component of a holistic approach) required more than two additional acres of space – an impossibility for the project site.
"We recognize that some buildings are able to achieve higher energy efficiencies by employing various holistic design approaches," said Bisacquino. "These approaches could become more economically feasible with new technologies and federal, state and local incentives."
NAIOP commissioned the study as a proactive approach to engage the commercial development industry in advancing an economically prosperous and sustainable built environment. "We are encouraged that study results show that increased energy efficiency and building profitability are not opposing concepts," said Bisacquino.