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Net-zero Energy Buildings

published: 2012-08-14 15:40

By D.A. Barber

Zero-energy buildings produce as much energy as they use through on-site renewable resources and efficient use “green” building techniques. This is no longer a lofty goal for residential building and now commercial building are being targeted.

Building structures account for nearly 40 percent of the energy consumed in the United States with a typical commercial building using an average of twice the energy of efficient buildings and nearly four times more of the most efficient buildings. Electric lighting in commercial buildings makes up 38 percent of total electricity consumption and lighting alone is the largest single drain, responsible for 20 percent of an individual building’s electricity consumption.

And the majority of commercial buildings in the U.S. do not have any building energy management system.

With roughly 80 billion square feet of existing commercial space in the United States alone, retro-fitting existing buildings is a vital but expensive way to meet climate and state energy policy goals. But a March 19, 2012,report from the New Buildings Institute (NBI) and the Zero Energy Commercial Building Consortium reveal that zero-energy commercial buildings are cropping up throughout the U.S. from California to New York and is the most comprehensive look at the state of zero energy commercial buildings to date.

The report, “Getting To Zero 2012 Status Update: A First Look at the Costs and Features of Zero Energy Commercial Buildings,” details the number, location, costs and design strategies of a number of these zero energy commercial buildings (ZEBs) as well as zero energy-capable (ZEC) buildings.

Instead of simply changing light bulbs, upgrading window insulation and going for LEED Platinum status, ZEB and ZEC buildings push the envelope of the latest renewable energy technologies.

Net Zero Energy Technologies

Net zero energy buildings are being constructed using readily available technology. With only 21 ZEBs and 39 ZEC commercial buildings in the U.S., the concept of energy self-sufficient commercial buildings is still an early trend, but the lessons learned from these early pilot projects an be applied to the general building stock.

The first step in creating a Net Zero Energy Building is reducing the energy usage by improving building insulation, reducing plug loads and installing an efficient HVAC system so the overall building electric load can be reduced dramatically. This means using an integrated design approach to a building’s layout, envelope, mechanical systems, and electrical systems to achieve the high levels of energy efficiency.

While building control systems have always been the most overlooked, underrated or subject to budget constraints in commercial buildings, today these systems are at the top of list of tech advances for both commercial and residential ZEBs. With lighting responsible for 20 percent of the total energy and 38 percent of electricity consumption in commercial buildings, lack of energy management controls can lead to 50 percent higher energy costs and add 25 percent more to the operations and maintenance budget, according to the NBI report.

Recent tech advances towards performance-based integrated whole building energy management control equipment options are providing one of the means of growth in both commercial and residential ZEBs, including the expanded use of analytics, occupancy sensors, lighting controls, plug load controls and energy management automation services.

NetZero Energy BuildingProjects

The New Buildings Institute report identifies 99 buildings that are either zero energy, zero energy-capable – both recently completed with limited performance data and currently under construction.

Among the innovative buildings is a 2,250-square-foot Net Zero Energy home in a suburban community of Silicon Valley, California. A 6.4kW PV system is designed to provide 100 percent of the electric use requirements for the residence which uses high efficiency LED and fluorescent lighting controlled by dimmers, timers and occupancy sensors. A planned expansion of the PV system will provide for electric vehicle charging.

Another project is the Schmidt Family Foundation Offices, a 4,000-square-foot former auto body shop located in California that was retrofit to go beyond a net zero building to a positive energy building. The 30kW PV system is designed to offset 100 percent of the building’s energy usage and then supply enough additional energy to charge 10 electric vehicles.

Commercial Homebuilders

Appliances and home electronics are responsible for about 20 percent of a U.S. home's energy bills, and heating and cooling homes accounts for nearly 60 percent of residential electricity usage. In the U.S., the big production residential homebuilders that construct multi-unit “communities” such as KB Homes, Ashton Wood Homes and Pulte Group have been using “green building” as a selling point and are even providing home “energy labels”.

The Arizona-based homebuilder Meritage is now constructing whole communities with solar-powered homes the company says will reduce utility bills by up to 80 percent.

Meritage also began offering custom built Net Zero homes in 2011. Meritage’s first net-zero home was built in their Verrado development in Buckeye, Arizona, using an Echo Solar System 15,000-kilowatt, 24-panel photovoltaic solar system

Meritage’s net-zero home

that also heats water and air for heating and domestic hot water use, by using 180-degree air that collects behind the solar PV panels. The company says the Echo Solar system produces two to three times more energy from the sun than a typical PV solar system since in addition to producing electricity, the system also captures thermal energy to heat and cool the home and water. Echo's Solar Control Center interconnects the water heater, solar panels, HVAC and thermostat to save energy.

Net Zero Conclusions

While in the past, ZEBs were primarily small, “demonstration” buildings, these projects are expanding in size and building type. Unique or experimental systems were frequently used to reach net zero goals, but the emergence of new technologies will be a factor in the expansion to more building types.

The New Buildings Institutereport contains recommendations to encourage this development, including cost information for owners and increased measurement of results on successful technology applications.

 “Lofty goals have been set for achieving zero energy buildings by 2030. This (NBI) study is a first look at whether we could possibly reach those goals. The really good news is extremely energy efficient buildings are being demonstrated in a multitude of climates and across building types. This is certainly a good sign for the future of zero energy buildings,” said NBI Executive Director Dave Hewitt.

Some recent studies suggest worldwide revenue from zero energy buildings will grow rapidly over the next two decades, reaching almost $690 billion by 2020 and nearly $1.3 trillion by 2035.

Much of this zero energy buildings growth will be driven by U.S. and European public policy. The UK is a good example: Buildings are responsible for almost 50 percent of the UK's energy consumption and carbon emissions. In the European Union, a new “Performance of Buildings Directive” is expected to require nearly zero energy construction for public buildings by 2019 and in all new construction by 2021. Starting in 2012, U.S. homes that get the “Energy Star” label will need to follow the new “Version 3” U.S. EPA efficiency standards that will require all new homes to use about 30 percent less energy than a typical house.

This move towards zero energy buildings should increase investment in building technologies required to make zero energy buildings possible, such as efficient lighting and HVAC systems, improved insulation, next generation BIPV, and building-based smart grid systems that allow easier interaction with plug-in electric and hybrid electric vehicles. This includes energy management systems important to monitor, regulate and control energy use in both commercial and residential buildings. In fact, both the green building industry and utilities are starting to embrace home energy management systems. These electronic energy management devices are getting smarter, less expensive, and reaching to Cloud  energy management automation services which should also trigger more sales of energy control systems in homes. This will become even more intense with the roll-out of smart grids that will require all homes and buildings to have “smarter” energy management.

For most buildings, the cost of PV was once the single largest cost for a building to become even close to becoming energy self-sufficient. But as PV prices continue to dive and more smart building and grid technologies become part of the “balance-of-system” costs, the overall economics of PV and other renewable energy generating technologies reaching grid parity seems to be more in reach as the push toward ultra-low or zero energy buildings is advanced by both a tight economy and mandated zero-energy buildings in new construction.

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