Fossil Ridge High School- LEED Silver

Overview

Starting in 2000, the Poudre School District opted to be an environmental steward.  Their goal was to meet the occupant comfort needs of their students and staff through the most energy efficient and environmentally sensitive means possible. Today their schools are providing superior learning environments, while reducing life cycle costs through conservation of energy 

“Poudre’s people stressed the importance of making sure all aspects of the project were interrelated. In other words, when we discussed landscaping and lighting, we had to analyze what effect it would have on the HVAC system and what effect the HVAC system would have on the irrigation system,” said George Brelig, the design architect at RB+B.

One of their schools, LEED Silver Certified Fossil Ridge HS, was awarded an ASHRAE Technology Award for its innovative integrated HVAC design and boasts an Energy Star score of 96. Their HVAC system is a prime example of the importance of integrated, whole building design. With all the building energy saving characteristics in place, the final ingredient was significantly downsizing the cooling plant with an Ice Storage system which optimizes efficiency while dramatically lowering peak demand. The end results are affordable green building design and construction as well as long term energy and cost savings for the school and Fort Collins community.

CHALLENGE

Their first step in attaining integrated success was to complete and submit a 69-page document entitled “Sustainable Design Guidelines.”  Two years in the making, that manuscript outlines the “desired performance outcomes from employing sustainable design and suggested approaches for attaining them”. These guidelines provide the framework for ways in which the district is to apply sustainability to the construction of Fossil Ridge as well as all new schools.

George Brelig, the design architect at RB+B recalls the importance that the district administrators placed on “Integrated Design.” “Poudre’s people stressed the importance of making sure all aspects of the project were interrelated. In other words, when we discussed landscaping and lighting, we had to analyze what effect it would have on the HVAC system and what effect the HVAC system would have on the irrigation system.” 

Green Building Compared to Traditional Building

The Integrated Design was a fundamental shift from certain aspects of conventional construction.  In order to determine the relative value of the integrated design, building designers did system analysis to compare Fossil Ridge’s level of energy consumption with that of a like installation.

SOLUTION

Fort Collins High School was used as a bench mark due to its similar square footage and because it serves a similar number of students.  Built in 1995 to the standards of that time, Fort Collins High School was not designed with Fossil Ridge’s energy conservation strategies. From its building envelope and orientation to its oversized boilers and cooling system, Fort Collins represents a ten year lag in sustainability know-how. It is partially air conditioned with a conventional chiller and cooling tower. It has T-8 lamps with electronic ballasts as well as variable frequency drives on the larger motors. Although it has good building orientation, the absence of Low-E glazing creates heat on the southern exposure in the summer and cold on the north side in the winter. 

    
Fossil Ridge High School was built, in 2004, with a budget of $36.2 million, while Fort Collins High School was built with a 1993 budget of $30 million. This, when adjusted for inflation, equates to a similar number to that of Fossil Ridge. Thus, Fossil Ridge showed that it could be a high performance building, while costing no more to implement than traditional designs.  

Fossil Ridge High School was built, in 2004, with a budget of $36.2 million, while Fort Collins High School was built with a 1993 budget of $30 million. This, when adjusted for inflation, equates to a similar number to that of Fossil Ridge. Thus, Fossil Ridge showed that it could be a high performance building, while costing no more to implement than traditional designs.  

Cost of Operating a Sustainable Design

Fossil Ridge High School (FRHS) of the Poudre School District in Fort Collins, Colorado, opened its doors in 2004.  After monitoring and comparing energy consumption and cost of energy figures, the Poudre School district proves that it also costs less to operate a High Performance school when compared to a traditional school.  

RESULTS

• Whereas Fort Collins H.S. peaked at about 800kW, Fossil Ridge peaks at 428kW, about half that of its older counterpart.
• Fossil Ridge used approximately $100,000 less in energy costs over the 2004-05 school year than Fort Collins High School, despite cooling the same amount of square footage.
• Fossil Ridge used 20 percent less kW in 2005, 23 percent less in 2006 and 31 percent less in 2007
• Fossil Ridge’s electrical costs were 27 percent less in 2005, 28 percent less in 2006 and 33 percent less in 2007
• For the 2007-2008 school year Fossil Ridge announced savings of $85,000

Fossil Ridge energy bills are about 33 percent less than those of a recently built, comparably sized high school in the district. Furthermore, this design costs no more to implement than traditional designs. Whereas typical school designs today use 3 watts / sq. ft.; FRHS uses only 1.6 watts / sq. ft.  Compared to Fort Collins H.S., Fossil Ridge High School required half of the peak electric demand. Electrical savings came primarily from lowering lighting and cooling loads during peak demand hours. Wherever practical, the district installed energy efficient T-8 lamps in Fossil Ridge, instead of traditional fixtures. As part of the same strategy, lights are automatically turned off when not needed and sensors adjust the lighting levels to supplement the amount of daylight that enters the room. Thus, during a sunny morning with the light entering from the east, the level of lighting is automatically decreased. Similarly, during overcast days, the levels are adjusted to provide the optimal amount of light for the classroom.

“We recommended tubular skylights for use in offices and restrooms,” adds Brelig. “These skylights bring natural light into the building and reduce electrical demand.” A tubular skylight captures sunlight on the rooftop, and then redirects it down a metal or plastic tube with a highly reflective interior coating. The reflective tube guides the sunlight to a diffuser lens mounted on the interior ceiling, which then distributes it into the building’s interior.

Energy Efficient HVAC Systems

The district called on McFall, Konkell and Kimball Engineers, Inc. of Denver, Colorado to find an innovative cooling solution that would cost less to operate. Their solution would prove to be a pivotal aspect in the design of Fossil Ridge since the heating and cooling needs are affected by virtually every other sustainable (or non-sustainable) characteristic of the building. After sustainable tactics such as thermal loads and building orientation are factored into the integrated design, the cooling system is down-sized.  The Rocky Mountain Institute calls this “tunneling through the cost barrier”. With significant down-sizing, efficiency of the equipment becomes less critical and the HVAC system can be designed for part-load efficiency. In addition, the downsized equipment can be selected to remain efficient over a wide range of energy load conditions bringing long-term savings to the District.

An IceBank® Energy Storage system from CALMAC was chosen to air-condition the school.  Ice Storage works like a battery that kicks in when extra power is needed. But instead of storing electrons, Ice is the stored energy. The cool energy is stored at night because it is more efficient to produce energy in the cool of the night than the heat of the day.  When it’s hot and demand is high, transmission line wires can lose up to 20 percent of the power pumped through them.  More importantly, shifting the cooling portion of the electric load from day to night, dramatically reduces the peak demand. In turn, reducing peak demand reduces the need for increased power supply resources and reduces pollution including green house gas emissions. Air-Conditioning accounts for roughly 40 percent of peak electric demand so reducing the peak demand is a critical aspect of green building and provides societal benefits. In fact, the Cost and Financial Benefits of Green Buildings remarked that “Energy benefits of green buildings need to be quantified not solely based on reduced energy use but also on reduced peak electricity demand.”   

At Fossil Ridge H.S., all of the Ice Storage cooling system equipment, including chillers, are properly downsized for part load efficiency, but are still able to handle peak electric loads. Take for example that most school designs call for one ton of cooling for every 500 sq. ft. of conditioned space. That means a conventional design would have required a 520 ton chiller and supporting equipment. Fossil Ridge, on the other hand, with its integrated design solutions reduced its maximum cooling load to 250 tons, which works out to be 1 ton of cooling for every 1,040 ft.  The cooling system was then designed for optimal efficiency by adding storage which allowed the chiller size to be reduced to 130 tons. The final design therefore works out to be 2000 ft. per installed ton of chiller.  It has a 250-ton peak cooling load that is completely met by four Model 1320C IceBank Energy Storage tanks and a right-sized 130 ton chiller.

Besides smaller cooling equipment, reducing peak demand also results in huge energy savings.It is very costly for utilities to build new power plants so they offer financial incentives to customers that reduce peak demand. Depending on the area of the country, considerations such as time of use rates (kWh) and charges for reaching varying levels of peak electrical demand (kW) (regardless if there is a flat rate), provide additional savings.  

Electricity during on-peak hours can account for more than 30 percent of the wholesale electricity costs even though peak hours are only 5 percent of the total . In Fort Collins, CO, the cost of a kWh is roughly $0.04 and the cost per kW is $12.00. The Fossil Ridge building design analysis showed that whereas Fort Collins High school peaks at 800kW, Fossil Ridge High School peaks at 428kW, approximately half the peak demand. This represents a significant cost savings to the district without sacrificing cooling comfort. Reducing the peak electrical demand, also helped Fossil Ridge earn LEED points. Due to the link between energy costs and source (power plant) energy savings, energy cost savings were used as the metric in earning LEED Credits in Energy & Atmosphere (Credit 1).

SUMMARY

Since it opened in 2004, the population at Fossil Ridge had grown to 2,063 students.Fossil Ridge was designed to use 60 percent less energy than a comparable, baseline high school and was expected to reduce energy costs by about 1/3 compared to comparable schools in the district, saving about $100,000 a year. As a result of its efforts, the Poudre County school district has been awarded the 2003 National Leadership in Energy Management, Sustainable-Design Award and the Media Center Design Award. Furthermore, 10 schools in the District have been designated Energy Star Schools.  The newest among the district’s five high schools, Fossil Ridge High School, has achieved an impressive Energy Star score of 96.  Fossil Ridge H.S. has also been recognized by the American Society of Heating, Refrigeration, and Air-conditioning’s (ASHRAE) Technology Award for New Institutional Buildings. It is also the first high school in Colorado to certify with the U.S. Green Buildings Council’s Leadership in Energy and Environmental Design (LEED) LEED™ Silver 2.1 Certified with a score of 36.

References:
U.S. Dept of Energy Center of Excellence for Sustainable Development
 

Table 1.
Tactics incorporated into Fossil Ridge H.S. in order to meet the standards set forth in the “Sustainable Design Guidelines”

• ~R-20 insulated walls and R-30 ceilings
• High performance/low E-glazing
• Proper building orientation to take maximum advantage of sunlight
• Superior, “right-sized” heating system including blower coils, condensing boilers, heat wheels, etc.
• Automated building system controls for all lighting and HVAC equipment
• Drought-tolerant native landscaping
• Sensors that adjust artificial lighting levels based on the amount of daylight in classrooms Tubular skylights
• Day lighting throughout the facility with north and south facing high performance windows as well as the use of strategically positioned exterior shading devices to minimize the direct solar heat gain component of the cooling load
• Ice Storage cools the building during peak electrical use by making and storing ice at night when the building has fewer electric loads, then using the ice during the following day.  Ice Storage meets entire electrical load after 10 a.m.

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