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Zero-Energy Strategies
“The key to achieving zero energy is drastic energy reduction and cost shifting to areas that pay dividends. It starts with efficient floor plans that are fully optimized (high net-to-gross ratio) and less expensive to construct,” explains Ben Robertson, an engineer with CMTA Inc. “Sure, any building can be zero energy—but doing it without spending more money is where true success is achieved.”
Although installing on-site renewable energy infrastructure such as solar arrays is coming down in price, it still requires an up-front investment. Making the building as energy efficient as possible helps to reduce the size of the renewable power infrastructure needed, thus keeping initial costs down. In addition, using cost-effective construction methods and materials allows room in the budget for the initial investment in power-generating equipment. The following are the key strategies to achieving these goals.
Passive Solar Strategies
Building orientation, daylighting, building volume, and thermal mass are all building properties that can be optimized by designers to help reduce energy consumption without increasing cost or compromising function and aesthetics. Passive solar strategies include:
- East/west building orientation: If possible, line up the building’s main circulation axis in an east/west orientation with academic spaces along the north and south walls of the building to control natural light.
- Daylighting: Use daylighting for classrooms with a combination of exterior solar shades to block sun during high sun orientation or light shelves to reflect light deep into interior spaces during low-sunlight conditions. Use clerestories or windows mounted at higher elevations with ceilings sloped to the interior to allow light to penetrate further. Use aerogel insulated glazing or low-e coatings to reduce solar heat gain.
- Compact building volume: Use rectangular, multistory designs (at least two stories) to reduce the exterior wall-to-floor area, window-to-floor area, and roof-to-floor area ratios.
- Thermal mass: Use building systems that have high thermal mass, such as concrete, for the walls and floors of the structure.
High-Performance Envelope and Structure
Sherman Carter Barnhart, along with other architects highlighted in the case studies below, have come to the realization that ICFs incorporate all of the properties needed for zero-energy school construction. ICFs are used for the following reasons:
- They act as load-bearing walls with super insulation, thermal mass, and air barrier all in one. ICFs create one of the tightest envelopes available. Low air-infiltration rates can be achieved with other systems, but it is significantly more complex.
- They reduce sound transmission from outside and between classrooms, as well as for gymnasiums, music rooms, and theaters.
- They keep students and teachers safe from Mother Nature’s wrath. Concrete systems are resistant to fire, tornados, hurricanes, floods, and earthquakes.
Energy-Efficient HVAC Systems and Technology
The use of energy-efficient mechanical systems and active-control technology is critical to keeping EUI as low as possible. Strategies include:
- Use efficient geothermal HVAC systems with variable-speed heat pumps. Use one heat pump for two classrooms.
- Use occupancy sensors for lighting and other occupancy dependent systems.
- Control outside air ventilation with dedicated outside air systems, heat-recovery wheels, and demand-control ventilation based on occupancy.
- Use automated dimming to reduce artificial lighting requirements. Although if using LED lighting, automated dimming can be eliminated since LED lighting is extremely energy efficient.
- Use ENERGY STAR convection ovens as a healthier option to traditional fryers and skillets, which eliminate the need for energy-intensive Type I ventilation hoods.
- Use ENERGY STAR laptops on carts that permit computers to be transported to classrooms instead of having dedicated computer labs with energy-intensive desktops.
- Use dark-sky approach to exterior lighting. Use security lighting with motion sensors to alert local police if there is activity on school property after dark.
On-site Power Generation
Most schools, including Richardsville Elementary, use photovoltaic panels as the main source of on-site power generation. Solar panels are becoming more common at schools across the United States. According to the Solar Energy Industries Association report titled “Brighter Future: A Study on Solar in U.S. Schools,” there are approximately 5,500 K–12 schools with solar photovoltaic installations in the country. A precipitous decline in the cost of solar panels has made installations financially viable. According to National Renewable Energy Laboratory, the cost of commercial solar installations has fallen to $2.80 per watt in 2017 compared to $7.24 per watt in 2010, a 60 percent decline in just seven years. This explains why 61 percent of the solar capacity in K–12 schools has been installed in the past five years.
With that said, there is still a capital cost of solar-panel installation that must be accounted for to meet the strict budget limitations of most school boards. The following are key strategies:
- Minimize the EUI of the building using all of the strategies previously mentioned. According to the New Building Institute, the target EUI for zero-energy schools is 20–24 kBtu/ft2 or lower if possible.
- During construction, utilize design strategies and building systems that are efficient and cost-effective to help offset the initial cost of solar panel installation.
Image courtesy of Sherman Carter Barnhart Architects and CMTA Inc.
East/west orientations, daylighting, and compact volume all helped to reduce the energy consumption of Richardsville Elementary School.
Richardsville Elementary School, completed in 2010, is the nation’s first zero-energy school. The 77,000-square-foot building combines drastic reduction in energy consumption with on-site photovoltaic panels that produce more energy than required to run the building. The building is so energy efficient that it returns energy back to the grid.
Photo courtesy of CMTA Inc.
Richardsville Elementary School in Warren County, Kentucky, is the nation’s first zero-energy school.
“We are tremendously proud that since its opening in 2010, we have not paid a single utility bill on Richardsville Elementary School. The reason for this cost avoidance is that the building actually generates more electricity than it consumes. At the end of the school year, we usually get a check back from the utility company in excess of $30,000,” says Jay Wilson, the director of safety and energy management for Warren County, Kentucky, Public Schools.
“The easiest way to increase a school district’s budget is to reduce its energy consumption,” explains Kenny Stanfield, a principal at Sherman Carter Barnhart Architects and an architect for Richardsville Elementary School, as well as dozens of other net-zero or near-net-zero schools located in Kentucky. “And the most cost-effective way to save energy is not to need it.”
Stanfield, along with CMTA Inc. engineers, lowered the energy use intensity (EUI) for Richardsville Elementary School to 18.2 kBtu/ft2 compared to 73 kBtu/ft2 required by the energy code, a 75 percent reduction. Because the energy use was so low and the building construction cost was below budget, the school district absorbed the cost of adding a 349 kW photovoltaic array to provide enough energy to power the school and sell a small amount back to the electric utility.
According to Stanfield, the trend toward zero-energy schools, or net-zero energy or zero-net energy, comes down to three factors:
- State-of-the-art design strategies and technologies to reduce energy consumption.
- An innovative building system such as insulated concrete forms (ICFs) that can provide high R-value and low air infiltration at a low cost.
- Affordable on-site solar energy.
There are several reasons why schools are ideal zero-energy candidates:
- Schools typically have low energy demand. They operate only nine months out of the year with well-defined and limited operating hours.
- Occupancy levels are predictable and controlled, and after-hour occupancy is limited.
- Plug loads are low compared to other building types that might run a lot of appliances and computer equipment.
- Schools are ideally suited for renewable energy, especially in the form of solar panels, since they are often limited to two stories and have a relatively large roof-area-to-volume ratio. This means that there is plenty of room to install solar panels. Most of the demand for energy comes during the day when the sun is available to generate electricity.
- Schools are owner occupied, which means that there is an interest in minimizing operating costs, including the cost of utilities. School boards have bonding authority to fund long-term projects.
- Schools can meet sustainability goals since zero-energy buildings reduce annual carbon emissions both through energy efficiency and the use of renewable energy.
- A healthier, more comfortable indoor environment can help stimulate learning, reduce student absences, and lead to increased teacher retention, according to the Center for Green Schools.
- Since many zero-energy schools are built using concrete construction with safe rooms and can generate their own power, zero-energy schools are disaster resilient; they can serve as a community shelter during and after a disaster.
Photos courtesy of CMTA Inc.
Richardsville Elementary School is so energy efficient that it generates enough energy to sell back to the electric utility.
Zero-Energy Strategies
“The key to achieving zero energy is drastic energy reduction and cost shifting to areas that pay dividends. It starts with efficient floor plans that are fully optimized (high net-to-gross ratio) and less expensive to construct,” explains Ben Robertson, an engineer with CMTA Inc. “Sure, any building can be zero energy—but doing it without spending more money is where true success is achieved.”
Although installing on-site renewable energy infrastructure such as solar arrays is coming down in price, it still requires an up-front investment. Making the building as energy efficient as possible helps to reduce the size of the renewable power infrastructure needed, thus keeping initial costs down. In addition, using cost-effective construction methods and materials allows room in the budget for the initial investment in power-generating equipment. The following are the key strategies to achieving these goals.
Passive Solar Strategies
Building orientation, daylighting, building volume, and thermal mass are all building properties that can be optimized by designers to help reduce energy consumption without increasing cost or compromising function and aesthetics. Passive solar strategies include:
- East/west building orientation: If possible, line up the building’s main circulation axis in an east/west orientation with academic spaces along the north and south walls of the building to control natural light.
- Daylighting: Use daylighting for classrooms with a combination of exterior solar shades to block sun during high sun orientation or light shelves to reflect light deep into interior spaces during low-sunlight conditions. Use clerestories or windows mounted at higher elevations with ceilings sloped to the interior to allow light to penetrate further. Use aerogel insulated glazing or low-e coatings to reduce solar heat gain.
- Compact building volume: Use rectangular, multistory designs (at least two stories) to reduce the exterior wall-to-floor area, window-to-floor area, and roof-to-floor area ratios.
- Thermal mass: Use building systems that have high thermal mass, such as concrete, for the walls and floors of the structure.
High-Performance Envelope and Structure
Sherman Carter Barnhart, along with other architects highlighted in the case studies below, have come to the realization that ICFs incorporate all of the properties needed for zero-energy school construction. ICFs are used for the following reasons:
- They act as load-bearing walls with super insulation, thermal mass, and air barrier all in one. ICFs create one of the tightest envelopes available. Low air-infiltration rates can be achieved with other systems, but it is significantly more complex.
- They reduce sound transmission from outside and between classrooms, as well as for gymnasiums, music rooms, and theaters.
- They keep students and teachers safe from Mother Nature’s wrath. Concrete systems are resistant to fire, tornados, hurricanes, floods, and earthquakes.
Energy-Efficient HVAC Systems and Technology
The use of energy-efficient mechanical systems and active-control technology is critical to keeping EUI as low as possible. Strategies include:
- Use efficient geothermal HVAC systems with variable-speed heat pumps. Use one heat pump for two classrooms.
- Use occupancy sensors for lighting and other occupancy dependent systems.
- Control outside air ventilation with dedicated outside air systems, heat-recovery wheels, and demand-control ventilation based on occupancy.
- Use automated dimming to reduce artificial lighting requirements. Although if using LED lighting, automated dimming can be eliminated since LED lighting is extremely energy efficient.
- Use ENERGY STAR convection ovens as a healthier option to traditional fryers and skillets, which eliminate the need for energy-intensive Type I ventilation hoods.
- Use ENERGY STAR laptops on carts that permit computers to be transported to classrooms instead of having dedicated computer labs with energy-intensive desktops.
- Use dark-sky approach to exterior lighting. Use security lighting with motion sensors to alert local police if there is activity on school property after dark.
On-site Power Generation
Most schools, including Richardsville Elementary, use photovoltaic panels as the main source of on-site power generation. Solar panels are becoming more common at schools across the United States. According to the Solar Energy Industries Association report titled “Brighter Future: A Study on Solar in U.S. Schools,” there are approximately 5,500 K–12 schools with solar photovoltaic installations in the country. A precipitous decline in the cost of solar panels has made installations financially viable. According to National Renewable Energy Laboratory, the cost of commercial solar installations has fallen to $2.80 per watt in 2017 compared to $7.24 per watt in 2010, a 60 percent decline in just seven years. This explains why 61 percent of the solar capacity in K–12 schools has been installed in the past five years.
With that said, there is still a capital cost of solar-panel installation that must be accounted for to meet the strict budget limitations of most school boards. The following are key strategies:
- Minimize the EUI of the building using all of the strategies previously mentioned. According to the New Building Institute, the target EUI for zero-energy schools is 20–24 kBtu/ft2 or lower if possible.
- During construction, utilize design strategies and building systems that are efficient and cost-effective to help offset the initial cost of solar panel installation.
Image courtesy of Sherman Carter Barnhart Architects and CMTA Inc.
East/west orientations, daylighting, and compact volume all helped to reduce the energy consumption of Richardsville Elementary School.
Low-Impact Development Strategies
Conserving water is another way to reduce environmental impact and construction cost. The following low-impact development strategies help meet zero-energy goals:
- Utilizing native plantings and rain gardens helps reduce irrigation demands.
- Using permeable pavements reduces stormwater runoff, filters stormwater, and reduces the need for expensive stormwater infrastructure.
- Permeable pavements and rain gardens can eliminate the need for detention basins, leaving more space for athletic fields and outdoor education opportunities for students.
Energize the Curriculum
Finally, make sure you engage the students and teachers by providing learning opportunities about energy efficiency and how the zero-energy building is helping reduce environmental impacts. Richardsville Elementary School used the following displays and interactive stations to help students visualize their contributions to reducing environmental impacts:
- Geothermal energy: Provide detail on how geothermal energy works, and expose piping with a temperature gauge so that students can monitor the system’s performance.
- Solar energy: Provide detail on how solar energy is captured and converted to electricity for use in the building. Provide a gauge to show how much energy is being produced. Provide a laptop computer battery-charging station where students can see the energy being received from the solar panels.
- Water conservation: Provide a station on water conservation that enables students to monitor the amount of rainwater collected and used in the rain garden.
Beyond Zero-Energy Schools
Schools are not the only building type going zero energy, nor are they the only building type using ICF construction. There are examples of high-performance ICF buildings all over the United States and Canada, including single-family residential, multifamily residential, hotels, dormitories, assisted living facilities, offices, health-care facilities, and manufacturing and warehouse buildings. Theaters are also trending toward ICF construction for superior sound attenuation.
Conclusion
Zero-energy schools are becoming more popular. High-performance envelopes using ICFs along with lower cost of renewable energy is making it possible. ICF systems result in construction that is faster, easier, and less labor intensive than other construction methods, making it possible to offset the cost of solar panels. ICF systems combine reinforced concrete with fire, sound, thermal, air, and moisture barriers in one step, which reduces the number of trades required on-site. Construction can continue all year long since the forms provide an ideal curing condition for concrete during the hottest and coldest weather.
All this leads to a construction system that is ideal to meet the demands of zero-energy buildings. ICFs create a modern building system that is easy to use and cost competitive. To find out more about ICF construction and concrete construction in general, visit www.buildwithstrength.com and www.icf-ma.org.
