Almost 48 percent of energy in the U.S. goes to residential and commercial buildings. Zero energy buildings drastically reduce that energy use by slashing the demand for energy, while supplying the remaining energy needs from renewable energy sources, such as solar panels. Zero energy buildings are connected to the grid, drawing power at night or during sunless days and sending power to the grid when the sun is shining. They not only cut net energy use and net carbon emissions to zero, but also lower cost of ownership and enhance the quality of life of their occupants.
The key components of a zero energy building include simple, off the shelf technologies beginning with energy modeling software, such as Energyplus for commercial buildings or REM/Rate for homes. This technology, used during the design phase, with the architect, engineer, general contractor, HVAC specialist and building energy consultant working together, helps determine the most cost effective mix of the following energy saving technologies needed to get to zero energy.
Insulation: The simplest measure on the path to zero energy involves increasing the insulation for the floors, walls and ceilings using standard insulation practices to meet the R-values set by the energy modeling.
Air Sealing: One of the most cost effective measures involves air sealing the building envelope to eliminate air leaks from the building structure itself and from around windows, doors, electrical outlets, plumbing fixtures and all other building penetrations. Air sealing is usually done with commonly used caulking compounds and foam products. Blower door technology to create a pressure differential within the building makes it much easier to detect air leaks, either by feeling the air flow or with a smoke stick.
Heating and Cooling: Ground-source and air-source heat pumps are effective energy efficient technologies for heating and cooling. Air-source heat pumps can now heat a building at outside temperatures as low as -10F. They can utilize central heating systems or smaller units such as mini-splits or package terminal units. New air-source equipment based on CO2 refrigerants offer even better performance. Dandelion’s new drilling technology promises to reduce the cost of ground-source heat pumps. Outside air can be used for cooling, using economizers connected to the HVAC system or automated windows.
Lighting: A well-designed zero energy building will take advantage of natural light by using properly oriented windows and louvres to direct the light where needed, while blocking heat when not needed. When artificial light is needed, LED Lights and point of use lighting greatly reduce the artificial lighting energy use and costs, while increasing lighting quality. Automatic lighting controls can lower or turn off artificial lighting when natural light is sufficient.
Windows: Double and triple pane windows are available with low-emissivity coatings that help capture or reject solar heat. Thermally-enhanced aluminum window frames reduce conductive heat transfer and can be very tight fitting,reducing air leaks and reducing external noise.
Shading Systems: Zero energy buildings are usually designed with roof overhangs or fixed awnings that are carefully calculated to shade the summer sun, but allow in the winter sun for solar tempering. This reduces heating and cooling costs and optimizes natural lighting. Automated internal shades use sensors to determine the need for blocking or allowing in sunlight depending on the heating or lighting needs. Electrochromic and thermochromic windows automatically darken when direct sunlight hits, which helps control heat, brightness, and glare.
Water Heating: In large commercial buildings with higher hot water use, a thermal solar system that circulates a heat-transfer fluid may be the best choice. For buildings with less hot water use, electric heat pump technology is very efficient. Even a well-insulated standard electric water heater, located near the points of use, powered by the solar PV system, can be cost effective. Drainwater heat recovery is effective where there’s a steady stream of warm waste water.
Appliances: Appliances, such as dish washers, dryers, and stoves, should be selected for the highest energy efficiency at the lowest cost, using those with ENERGY STAR ratings when possible. High RPM washers spin so fast that most of the water is squeezed out of the laundry, making drying the clothes much quicker. Induction stove tops and heat pump driers are exciting energy-saving technologies already in use.
Ventilation: Because zero energy buildings are so airtight, an energy efficient heat recovery ventilation system is required to provide fresh filtered air. Since studies have shown that indoor air quality is worse than outdoor air quality, a ventilation system improves the health and wellbeing of the building occupants.
Solar PV: Based on energy modeling, the photovoltaic system is best sized after all other energy saving measures have been determined. Photovoltaic systems are extremely durable and long lasting and their price has come down significantly. They produce DC current that is converted to AC by an inverter so it can be used for normal building uses. Using net metering, when the photovoltaic array makes more energy than is needed, it is exported to the grid and when it needs energy, it draws from the grid.
Building Integrated Photovoltaics: Large multi-story commercial buildings may have too small a roof area for the number of solar panels required to meet the building’s energy needs. In such cases, PV panels can be integrated into other building surfaces. There are even window glazing systems that use photovoltaic technology to generate electricity.
On-site Batteries: All buildings pay for the energy they buy from the utility grid based on rates determined by demand. On-site batteries can dramatically reduce demand charges by storing excess solar energy that is used for the high-rate periods of peak demand. Sophisticated energy
management systems can control this process for optimum financial benefit.
Energy Efficient Workstations: Using daylighting, workstations can be brightly lit using little energy. When natural light is not sufficient, point of use LED desk lights are very efficient. Energy-efficient lap top computers can be used, and phantom loads reduced.
Phantom Load Reduction: Electronics and appliances use power when turned “off,” which represents a significant energy drain. In some electronics, this standby mode accounts for the majority of the device’s annual energy consumption. These include remote controls, lights or displays that stay on after turning them “off,” or cords that incorporate a “power brick”. The simplest solutions include developing protocols for unplugging devices when not in use and utilizing “smart” power strips. Smart technology is now available that can automatically kill all phantom loads when devices are not in use. Laboratory and Kitchen Exhaust Fans: Inefficient exhaust fans use extra energy and pull conditioned inside air out of the building. ECM fans use less energy and insulated external flaps can reduce heat loss. In many laboratories, fume hood sashes are left open even when unattended. Simple “Sash Hood Stickers” attached to the hood encourage lab workers to close the sash hoods when not in use. In some labs, energy use is so intensive that a comprehensive management approach to reducing energy use is required. With their specialized equipment and high ventilation needs, it is a challenge to get laboratories to zero energy, but a few laboratories have already succeeded, such as the J. Craig Venter Institute’s biological laboratory.
Smart Energy Management Systems: Energy Management Systems can kill all plug loads when occupants leave, adjust each room’s temperature using sensors to determine if they are occupied, adjust internal shades or external louvres to optimize temperature and lighting, adjust the level of artificial lighting based on the amount of natural lighting and on the presence of people in the room.
Zero Energy Construction Costs: It is common that the energy saving features and photovoltaic systems increase the cost of construction. However, according to EERE, zero energy commercial buildings can be built within typical construction budgets; and even zero energy Habitat for Humanity homes for low-income families can be built for less than standard Habitat homes. To achieve these goals in large projects, Energy Performance Based Procurement guidelines, based on energy modeling, can be followed.
Return on Investment in Dollars: Even when zero energy building costs are higher, they will cost less to own, because the added cost for the energy improvements over and above the costs of a similar standard building, when rolled into the mortgage, will lead to a smaller additional monthly mortgage cost than the savings on energy each month.
Return on Investment in Quality of Life: Another important return on investment is in quality of life. Zero energy buildings have fresh filtered air, are draft free, have even temperatures, and are better lighted and quieter—all of which improve the health and well-being of the occupants. The wellbeing of employees is a significant benefit to the bottom line of owners. All the technology for zero energy buildings is currently available and in wide use. Zero energy buildings cost less to own than similar standard buildings, enhance the quality of life of the occupants, and are essential to meeting the world’s climate goals. It is simple, available, winning technology, whose time has come.
About Zero Energy Project
The Zero Energy Project is a non-profit educational organization whose goal is to help home buyers, builders, designers, and real estate professionals take meaningful steps towards radically reducing carbon emissions and energy bills by creating zero energy.