A Nearly Carbon Neutral Campus Building: How Far Can We Go?
October 1, 2007
At this university in Maine, a geothermal system, VSDs, and controls that monitor CO2 and daylight lead the charge against conventional energy consumption. See how the equipment complements other measures like a green roof and renewable power purchasing in the project’s effort to move to the head of the class.
Colleges and universities are increasingly embracing green design as a way to position themselves as eco-friendly institutions. Many are learning that what initially may have been another way to meet potential student expectations actually provides benefits well beyond marketing. Measures taken to create a sustainable campus are becoming necessary and provide economic benefits. In 2004, the University of Southern Maine (USM) in Gorham celebrated the opening of the John Mitchell Center, the first state-owned building to achieve LEED® certification. Not only did the project show what can be done, it whetted the university’s appetite to go further in sustainable design.
Currently, our firm is working on the design for the Osher Lifelong Learning Institute (OLLI)/USM Muskie School of Public Service (The Wishcamper Center) project. USM’s goal for this building was to achieve a LEED Gold certification and to leave a very low carbon footprint.
The Osher Institute will be a 56,000-sq-ft, three-story building that incorporates a number of innovative green and sustainable systems and creative ideas into the design to reduce carbon use and maximize energy efficiency. Some of these include:
- Geothermal heating/cooling
- 50% renewable power purchase agreement
- Daylight harvesting
- Demand controlled ventilation through occupancy control
- Instantaneous domestic hot water
- Harvested rainwater and geothermal well bleed water
- Partial green roof
- CO2 monitoring for ventilation air quantity/quality
- VSDs on motors above 3 hp
- Multiple means for public transportation to campus – campus shuttle and city bus line
- No on-site utilization of fossil fuels
Geothermal Heating and CoolingThe team analyzed various heating and cooling system options. A central oil/gas-fired steam plant currently serves the campus. The site selected for this new facility is currently not on the campus steam loop, and extending the steam to its location would’ve meant a significant additional expense. Also, the campus plant heating redundancy would be compromised if the additional heating load were added. The idea of geothermal cooling and heating was developed to accomplish four goals:
- Avoid the use of carbon-based fuels on site for building heating.
- Avoid extending expensive central plant line to the site.
- Avoid reducing central plant redundancy.
- Provide cost-effective cooling and heating to the building.
The geothermal system comprised the following:
- Eight 35-ton water-to-water heat pumps stacked in a basement mechanical room
- Heat pumps piped (in a four-pipe arrangement) to building air-handling equipment and stacked finned tube radiation
- Five 1,500-ft-deep standing column wells, with each well designed to provide 500,000 Btuh
From the heat pumps, the water temperatures supplied to the building will be 45
Renewable Power PurchaseThe university has established a practice of purchasing renewable green power. The purchase contract established for this building will be for 50% of the electrical power used in this building. The total contract will be for approximately 500,000 kWh/yr.
Daylight HarvestingThe design of the Osher Institute integrates a significant quantity of glazing. Working with the designers, the type of glass, shading coefficients, and thermal conductance of the glass were thoroughly discussed. Fritted glass was decided upon due to the improved shading coefficients, as well as the improved natural light quality, which is allowed through this product.
Fritted glass impedes ultraviolet rays, which consequently reduces the solar heating impact when compared to plate glass. The use of this product reduced glazing/solar cooling loads by 15%, resulting in an overall reduction in the cooling load of 8%. Also considered when evaluating glazing systems was the light quantity and quality. Harvesting natural daylight through fritted glass provides a higher quality of light for building occupants due to the ability of fritted glass to reduce the quantity of visible spectrum light and consequently reduce glare. This combination of glass performance was incorporated into a natural daylight automated control system, which will use light sensors and occupancy controls to turn on artificial light in the open forum and gathering spaces only when required.
Demand Controlled VentilationThe building’s program includes office spaces, lecture halls, and classrooms. Due to the potential of intermittent use of the lecture halls and classrooms, we’ve incorporated a demand controlled ventilation strategy. Using infrared occupancy sensors, ventilation air will be monitored, controlled, and supplied only when a classroom or lecture hall is occupied. This strategy, which will reduce fan energy consumption and tempering of non-required ventilation air, will save $6,200 in operating costs annually.
Domestic Hot Water UseIn planning the building and its use, the need for significant domestic hot water for showering was mitigated due to a campus decision to allow the building occupants to access an adjacent building’s locker room facility. This allows for the use of source instantaneous domestic water heating. No storage tanks or recirculation piping were required. The domestic hot water is generated on demand at the source location.
Harvesting Rainwater And Geothermal Well Bleed Water CaptureThe desire to minimize use of potable water for flushing of fixtures was accomplished by integrating a 5,000-gal concrete storage vault. This vault will collect rainwater from roof drains as well as the bleed water from the five geothermal wells. The vault’s contents will be filtered, scanned by ultraviolet light - to kill any organisms - and pumped to all flushing fixtures in the facility. The designed systems include waterless urinals and 1.6 gal/flush water closets. The combination of the harvested rainwater and bleed water capture system should allow the university to avoid using any potable water to flush fixtures. This avoids the waste of 560,000 gal of potable water annually. The estimated cost for the rainwater harvesting system is $46,000.
Partial Green Roof
A partial green roof was integrated into this project. This is the first green roof experience for USM, consequently the partial green roof is a first step for the university. The green roof area is 1,600 sq ft; the remaining membrane roof is 12,000 sq ft. The 1,600-sq-ft green roof helps with the impervious surface calculations for water run-off as well as reduces the cooling load in that area, resulting in a 50% reduction in conductive heat gain. With the successful service of this green roof, expanded use of this type of product on future projects is anticipated.
CO2 Monitoring For Ventilation QualityCO2 monitoring of these spaces - which maintains a CO2 differential between outside ambient conditions and indoor conditions of 530 ppm - allows the building systems to be optimized. Only the required ventilation air will be supplied to maintain desired CO2 levels. The alternative to CO2 monitoring and control would be to provide a full volume of conditioned outside air to an occupied space regardless of occupant loading.
VSD MotorsVSDs for both fan and pump motor capacity control have been specified. ASHRAE 90.1 2001 does not require the use of VSDs on fan motors of a size less than 30 hp and on pump motors less than 50 hp. This project has eight air fans and four water circulation pumps, which are less horsepower than the ASHRAE guide identifies, all with VSDs. This integration of technology presents an annual electrical energy savings of $12,500/yr. The cost premium to include the VSDs in lieu of standard motor starters and bypasses is $34,000. The simple payback equates to 2.8 years.
Non-Technical MeasuresTransportation to and from campus and within campuses for the University of Southern Maine has been accommodated through public transportation, shuttle bus, and the use of zip cars (a car share service). USM has two campuses, one in Portland, and one nine miles away in Gorham. The use of the shuttle service, public bus service, and zip cars is an attempt to minimize the need for large parking facilities and individual vehicle trips to and from the campuses.
The university also has a no smoking policy on campus, which reflects the healthy and environmentally sensitive position the campus embraces.
The building and its design features represent the university’s commitment to encouraging sustainable and environmentally friendly campus practices. The final carbon footprint for this facility is currently being developed. The combination of technical energy saving measures and campus policies regarding transportation and facility resource sharing (showers/lockers) combine for a responsible, efficient, and low carbon footprint project. ES