Trends In Green
Turn It Up to Zero
Practical strategies for moving toward net-zero energy.
- By Ian Hadden
- October 1st, 2013
By any measure, the New Elgin K-12 school is an energy-efficient building. Located in north central Ohio, the school opened in 2013 and is projected to reduce energy costs by 37 percent compared to the baseline established by existing codes. Elgin is designed to achieve LEED Silver certification and has already earned “Designed to Earn the ENERGY STAR” status from the U.S. Environmental Protection Agency. But what would it take for a building like Elgin K-12 School to go farther—all the way to net-zero?
When it comes to net-zero buildings, renewable energy strategies often get the headlines. But energy efficient design is just as important. Typically, a net-zero building the size of the Elgin K-12 School would use 20 kBtu/SF/YR, or less. While Elgin is in the top 90 percent of energy efficient buildings in its area, the school’s projected energy use is still 29.5 kBtu/SF/YR. That is 33 percent more than a net-zero ready building.
How do you make up the difference? To start, many school facilities are oriented for street views rather than solar angles. To reduce heat gain, north and south facing glazing should be maximized and east and west exposures should be minimized. It also beneficial to determine the direction of prevailing winds and potentially seek or create natural wind breaks. This impact can be significant.
Energy modeling is a key tool when teams seek to design a net-zero-ready facility. Computer models allow the design team to explore interrelationships between building components and parameters. The result is a design that is customized for that particular location. In some areas, that will be a super-insulated envelope. In mild climates, the focus will be on infiltration, rather than insulation levels.
Other net-zero strategies are found in the kitchen. Not surprisingly, a typical school kitchen uses a tremendous amount of energy to prepare food each day. Transitioning from natural gas-powered stoves to electric stoves allows the entire kitchen to be served by solar power. Eliminating fryers in the kitchen will reduce the building’s overall ventilation loads, and the use of ENERGY STAR rated appliances increases efficiency.
LED lighting is another efficient strategy, and is increasingly becoming a cost-effective option for all parts of a school building. LED luminaries, combined with daylighting harvesting of natural light, reduce the overall electrical load.
Identifying renewable resources
By definition, a net-zero building has enough on-site renewable energy to supply 100 percent of annual resource consumption. Typically, cost-effective options are limited by geography and climate. Solar options are popular in the western parts of the United States, while geothermal systems are popular throughout the Midwest.
In fact, the new Elgin K-12 School does have a ground source heat pump system. The site includes a 3.5-acre storm water retention pond. The bottom of the pond is lined with geothermal loops that are connected to energy-efficient heat pumps throughout the building.
For schools throughout the country, solar power is typically a viable option only when combined with utility rebates or energy credits. Crystalline silica photovoltaic (PV) panels provide up to 14 Watts per square foot. As these panels become more efficient, the additional cost of solar power becomes more reasonable. Many schools have started future proofing their new buildings with roofing systems design for PV panel loads (about three pounds per square foot) and electrical conduits ready and waiting to carry sun-driven electrons throughout the facility.
To reduce the initial costs associated with renewable energy, it is important to properly size these systems. Renewable sources should be sized to provide 50 to 75 percent of the building’s full summer demand. If systems are oversized, a school may actually spend more money to generate energy than it will earn when excess power is sent to the grid.
Heading toward zero
Net-zero buildings represent the next great milestone in the sustainable revolution. While educational facilities such as Elgin K-12 School demonstrate the strong emphasis that communities place on sustainability, there is even more we can accomplish. Doing so will take a new approach to how schools are planned, designed, constructed and operated. However, by incorporating even some of these strategies, educational communities, students and the environment will greatly benefit.
This article originally appeared in the October 2013 issue of School Planning & Management.