GLUMAC - Engineers for a sustainable future

Lauren Kuntz, LEED^®AP, San Francisco Commissioning Agent

Computational Fluid Dynamics (CFD) modeling is a computational technology which evaluates numerical methods and algorithms to simulate fluid flow. In the building industry, this technology is used to generate a visual representation of a building's airflow, flow rates, and space temperatures. Recently, Glumac generated two CFD models to evaluate the airflow through, and assist in the design of, two new naturally ventilated buildings on Branson High School's campus in Ross, California in Marin County.

Hui Jin, a CFD analyst with a PhD from UC Berkeley, and formerly from UC Berkeley Center for the Built Environment (CBE), recently joined Glumac to assist in designing buildings with underfloor air distribution and natural ventilation. His first project with Glumac was to analyze the natural airflow through two proposed new buildings in the Branson High School Tenant Improvement project.

The Branson High School project consists of a new student commons building and fine arts center, and is pursuing LEED Platinum certification under the LEED for Schools program. Once certified, it will be the first LEED for Schools Platinum Certified project in California. In addition to providing CFD modeling services and assisting with LEED documentation and certification, Glumac is the fundamental and enhanced commissioning agent for the project.

The building designs proposed by Turnbull Griffin Haesloop (TGH) Architects along with regional wind and weather data from Ross, CA were combined to generate the CFD models. The goal of the models was to demonstrate compliance with American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) Standard 55 for Thermal Comfort and Standard 62.1 for Ventilation. Compliance with these two standards will satisfy Prerequisite 1, Minimum Indoor Air Quality (IAQ) Performance as well as earn Credit 2, Increased Ventilation and Credit 7.1, Thermal Comfort Design in the Indoor Environmental Quality category of LEED for Schools.

The CFD analysis determined that the fine arts center, as designed, met both the ventilation and thermal comfort requirements set forth by ASHRAE. However, although the student commons building design met ASHRAE's ventilation requirements, it fell short of meeting the thermal comfort criteria. The design did not allow the necessary amount of outside air to flow into the building during the hot summer months to provide adequate indoor thermal comfort. Due to the high occupancy in the dining hall, and the heat introduced to the area from the kitchen, higher volumes of outside air were required to remove heat from the building than were being introduced in the original design.

Through the findings of the CFD analysis, Glumac was able to determine the problem areas of the building and relay this information to TGH. Together, they analyzed the windows in these problem areas and identified which windows could be changed from fixed to operable, in order to allow the proper amount of outside air to enter the building and maintain proper thermal comfort.

The Branson High School project demonstrates the importance of CFD analysis for naturally ventilated buildings early in the design phase. Because of CFD modeling, the design team was able to identify possible thermal comfort problems early on, before the building was constructed. The analysis was also able to demonstrate compliance with ASHRAE 55 and 62.1 standards, which will facilitate the Branson High School project in earning LEED for Schools Platinum Certification.