Sebesta Inc.: University of Minnesota Itasca Biological Station and Laboratories
New construction of an educational facility.
Engineering firm: Sebesta Inc.
2014 MEP Giants rank: 32
Project: University of Minnesota Itasca Biological Station and Laboratories
Address: Lake Itasca, Minn., U.S.
Building type: Educational facility
Project type: New construction
Engineering services: Automation/controls, electrical/power, HVAC/mechanical, lighting, energy/sustainability, and plumbing/piping
Project timeline: 7/26/2012 to 7/18/2014
MEP/FP budget: $4 million
Sebesta joined the project in progress for the development of a new campus center on the rustic-style 70-building University of Minnesota Itasca Biological Station and Laboratories. The project is intended to be a net-zero energy building, setting the model for future projects and renovations of existing facilities. The design team realized early that the key to the development of a high-performance building would be the implementation and management of a committed, integrated design approach. With a limited budget, some of the key design challenges and strategies were heating and cooling, ventilation, and lighting that would meet the energy goals of the project. Many difficult decisions and trade-offs were made while determining optimal building systems. MEP design specific goals included:
- All occupied spaces need to be provided with natural daylight.
- All occupied spaces should have capability of natural ventilation, given the climate conditions of the site.
- The common lobby area and the lab corridor, known as the "sun corridor," was to be minimally conditioned in winter and not be actively conditioned in summer.
- Ground source heat pumps were to be the source of winter heat/summer cooling.
- The system was to be designed to accommodate future expansion into the campus at large, and include an exterior vault sized to handle a future expanded geothermal well field for this purpose.
- Sensible heating and cooling need to be served by a radiant floor slab and zoned per major group occupancies.
- Ventilation needs to be served by a dedicated outdoor air system (DOAS), which would deliver conditioned outdoor air to each occupied zone via displacement ventilation floor diffusers. The outdoor airflow rate is based on zone level CO2 sensors. The DOAS unit is provided with total (sensible and latent) energy recovery.
In developing a net zero energy project it is important to engage in early, active, and continuous collaboration, including the contributions of the construction team during the design phase. A two-day predesign retreat on the site was held to bring the team together to help progress the project team through the design phase and create an atmosphere of creative solutions and understanding. MEP design solutions included the following:
- Geothermal was selected since natural gas was not available on-site. When compared with the alternative of propane for heating and condensing units for cooling—the current method of conditioning campus buildings—geothermal stood out as the best alternative. Geothermal also allowed for expansion to other campus buildings, consistent with the overall campus master plan.
- Radiant heating and cooling was selected as a perfect strategy for this project. The low energy temperatures of a radiant system provided optimal energy efficiency as well as optimal comfort. Radiant cooling would be a suitable means to serve the sensible cooling loads, while the DOAS handled the latent loads and supplemented the sensible cooling on peak cooling days.
- A photovoltaic (PV) system was determined to be the best option for an on-site renewable energy source sized to produce energy and meet the building’s demand goals. The strategy of PV offsetting building energy consumption posed the challenge to address the natural trade-off between building energy performance and the size of the PV array required to achieve net zero. This was addressed by trade-offs between combinations and optimization of building elements. The capacity of on-site generation was determined to be optimal at 40 kW. This size of the PV field would produce an offset for the building, and the envelope, lighting, and mechanical systems were then focused in to provide the necessary energy performance. A shading analysis was conducted in final checks to insure the PV array performance would not be impeded throughout the day.
- Optimal use of natural ventilation would require complete automation with no manual control. This was not acceptable to the university, nor was it in the project budget. The university chose to take on the risk of sub-optimal manual control of the natural ventilation systems.
- Using SketchUp and Revit as common BIM tools, the design team could easily share modeling information, allowing all groups to independently create energy, daylight, natural ventilation, and thermal mass studies sharing the same base. The project is nearing substantial completion with targeted occupancy in July 2014.