Ambient Energy: Colorado State University

IESVE software proves Energy, Daylight and Mixed-Mode ventilation concept for Colorado State University Atrium

Colorado State University
Established in 1879 in Fort Collins, Colorado State University is home to nearly 30,000 students and more than 1,500 faculty members. The Engineering II building, located on the North edge of the campus, features classrooms and administrative offices as well as a research laboratory, rooftop data center and three-story covered atrium. Its sustainable renovation had to achieve low carbon, highly efficient targets with good occupant comfort.

The Project
The atrium of the Engineering II building represents a unique space, with students passing through 24 hours a day for their studies and research projects. With the goal of creating a “home-away-from-home” environment, University officials sought to renovate the building to be a place where students and faculty could feel comfortable and experience natural daylight, views and ventilation. Officials also wanted the atrium to be highly efficient, keeping carbon emissions and energy costs to a minimum. With students and faculty occupying the building at all times of the day, officials were faced with a particularly difficult challenge: ventilating the atrium while maximizing the use of daylight to naturally light the space. A stringent temperature comfort range meant both daylighting and ventilation had to integrate flawlessly, as the minimum temperature could not drop below 66 degrees Fahrenheit and the maximum could not exceed 77 degrees Fahrenheit.

The Analysis
University officials enlisted Ambient Energy, a consulting and engineering firm specializing in sustainable technologies and building, for the renovation. Using IES VE-Pro software, Ambient Energy engineers were able to test and verify the architectural and passive strategy concepts for the atrium before implementing them. Initially, wind and climate analysis gave a better understanding of how natural factors would impact the building. Analyses showed that because of varied wind direction, natural ventilation would rely predominantly on buoyancy instead of wind driven data.

Daylight, bulk airflow and micro CFD airflow analyses run early in the schematic redesign process determined which window and ventilation solutions would work best to maximize use of natural daylight and natural ventilation. Linda Morrison, Building Performance Engineer at Ambient Energy, noted that “VE-Pro is one of the only tools that can provide integrated daylight, thermal and mixed-mode ventilation analysis in great detail, which allowed us to test the integration of all components across the year.” The performance analyses also helped ensure that the atrium would perform according to the strict temperature guidelines, providing the proof facility staff needed to sign off the final design strategy of operable windows with automatic controls.

Ambient Energy integrated information from Revit into IES flawlessly by ensuring they spent time with the architects to explain the small additional steps required for an optimum gbXML import. “We had a completely successful import into IESVE, which shows it’s very attainable to do this process with the BIM benefits for all,” Morrison said.

The Results
IES’ VE-Pro software provided engineers with highly detailed daylighting, mixed-mode ventilation and energy simulations that played an integral role in the design process. Verifying efficiency solutions allowed engineers to move forward with only those that the simulations proved viable. The MacroFlo bulk airflow tests confirmed that natural ventilation would provide effective cooling driven by buoyancy pressureinduced airflow and would adequately cool occupants on all three floors through March to October, with a natural ventilation rate of between 1200-1400 CFM. MicroFlo tests used micro CFD analysis to prove that fan-assisted air flow was actually detrimental to the way air moved throughout the atrium, and was not required. Similarly, skylights were shown to allow more natural light to filter into the space than tubular lighting.

These results led designers to opt for natural ventilation and install automatically controlled operable windows on the first and top floors on both the East and West sides of the building in order to keep temperatures and airflow comfortable. Any time the indoor temperature was 73 degrees Fahrenheit or greater and the outside air was between 50 and 73 degrees Fahrenheit, natural airflow was used for ventilation and cooling. This significantly decreased energy consumption associated with air conditioning. The decision to install skylights in lieu of tubular lighting also cut energy consumption by diminishing the need for artificial light sources.

Summary
By providing tangible data early in the schematic redesign process, IES’ VE-Pro provided designers and their clients with a way to test and verify their building efficiency theories before putting them into practice. This led to the effective utilization of skylights and natural ventilation to improve daylighting, cooling and energy efficiency in the atrium. Ambient Energy has been using IES’ software for several years and utilized its capabilities on many projects to prove concepts and radically reduce building energy consumption. “IES helped us with the bottom line: a low carbon, highly efficient, well performing atrium,” Morrison said.

In June 2011, Linda Morrison, Building Performance Engineer at Ambient Energy, presented on how to achieve improved energy performance with an integrated design process, citing IES’ software, at a local U.S. Green Building Council chapter meeting in Denver, Colorado. In response to the presentation, one attendee remarked, “Of all the modeling tools out there, IES is number one!”