Sustainability – Net Zero Energy Buildings

Sustainability quickly became a buzz word among our industry. Designs, products and regulations are changing faster than ever before. Owners and clients all seem to be on-board with becoming sustainable and going ”green”. The future of sustainable design is in the concept of Net Zero Energy Buildings.

What Is The Definition Of a Net Zero Energy Building?

Net Zero Energy (NZE) buildings have had many different definitions over the years, but in 2015, the DOE released the following definition:

“an energy-efficient building where, on a source energy basis, the actual annual delivered energy is less than or equal to the on-site renewable exported energy.”

NZE represents the highest level of sustainability; it is the next step in distinguishing one green building from another. Net zero energy is being promoted by many different organizations in the construction and building design industry:

  • The International Living Future Institute (formerly USGBC Cascadia) runs its Living Building Challenge, which challenges designers in seven areas: site, water, energy, health, materials, equity and beauty.
  • The Architecture 2030 Challenge, which sets increasing goals over the next 20 years, is also pushing implementation of NZE. The goals in the challenge call for buildings to use 70% less energy by 2015, 80% by 2020, 90% by 2025, and finally to become carbon neutral by 2030.
  • ASHRAE has its own Vision 2020, which is a pledge to make the tools necessary to design, build, and operate NZE buildings by 2020.

A Look At Current Building Energy Usage

Right now, an average commercial building consumes roughly 90,000 btu/sf/yr. A new building, built to the current national energy standards and codes, would consume roughly 70,000 btu/sf/yr. Finally, current buildings that are operating at NZE levels are consuming less than 20,000 btu/sf/yr. That is more than a 70% cut from current energy standards and codes; quite a daunting number.

Studies by the National Renewable Energy Lab show that only a small portion of existing buildings are good candidates for NZE. Some of the best candidates include: Low-rise buildings, unrefrigerated warehouses, churches, retail, schools, assemblies, and out-patient healthcare. Some of the worst candidates are: hospitals, labs, skilled nursing, restaurants, and refrigerated warehouses.

The major factor in determining good building candidates from bad one are plug and process energy needs. Buildings with the lowest plug and process energy needs make the best candidates for NZE operation. Building area is an additional hurdle to overcome in creating NZE buildings. The current largest NZE building so far is only 13,600 sf.

Currently there are very few buildings that have achieved NZE operation as listed by the U.S. Department of Energy, but that number is expected to grow rapidly over the next 10-20 years.

What Are The Characteristics Of Net Zero Energy Buildings?

NZE buildings have common elements and components, in both the design process and the operation phase. One of the most important elements in the design process is close and careful coordination between designers and occupants. Equipment usage scheduling is absolutely necessary, on both a daily level as well as a seasonal level.

Designers must use energy modeling to help ensure that expected energy demands stay low enough to be fulfilled by energy production. Some common trends seen in HVAC include radiant heat usage, ground source heat pumps, and heat recovery. Efficiency in all parts of design is imperative, including appliances, lighting, and HVAC.

Some passive building design features include: orientation, insulation, internal masses, glazing and shading, passive solar energy, daylighting, and natural ventilation.

Finally, buildings need a way to generate their own energy sources. Some of these methods currently include water or wind turbines along with photovoltaic systems. These are the tools and practices that we as professionals in the industry must begin to adapt to and apply as we move forward to more sustainable designs over the coming years.

A Look To The Future

History has shown us that change in the building design industry can be slow moving. The development of LEED over the last decade has shown us, though, that change can become very fast moving if an advantage is offered to building owners. Net zero energy buildings provide that advantage.

Public awareness of NZE design benefits must be raised, along with responsible owners who are committed to NZE design, construction, and operation of buildings. As professionals in the construction and building design industry, we are responsible to be prepared for NZE design and construction. This next step in building design will quickly become the now before we know it.

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