One of the problems in the green building world is the lack of clarity in the terms used. I have been complaining about the term Net Zero Energy for years, claiming that it had little to do with green building at all, that "you can make a canvas tent net-zero if you have the money to put enough solar panels on it." There was no real satisfactory definition, no rigorous certification.
That is not true anymore; the Living Building Challenge has developed the Net Zero Energy Building Certification and it is rigorous indeed. They note the need for it:
The certification verifies that the building actually operates as claimed, "harnessing energy from the sun, wind or earth to exceed net annual demand." It can't be a canvas tent, either; there are other requirements from the Living Building Challenge that must be considered:
Net Zero Energy is quickly becoming a sought after goal for many buildings around the globe - each relies on exceptional energy conservation and then on-site renewables to meet all of its heating, cooling and electricity needs. Yet the true performance of many developments is overstated – and actual Net Zero Energy buildings are still rare.
- Limits to Growth (in part): Curbs the building’s contribution to the effects of sprawled development, which undermines the positive impact of achieving net zero energy building operation.
- Net Zero Energy: Serves as the primary focus of Net Zero Energy Building Certification.
- Rights to Nature: Ensures that the building does not preclude another building from achieving net zero energy operation as a result of excessive shading.
- Beauty + Spirit and Inspiration + Education: Underscore the notion that renewable energy systems can be incorporated into a building in ways that are attractive and inspiring.
A good example of a Net Zero Energy Certified building is the The David and Lucile Packard Foundation in Los Altos, California. The building was predicted to consume 247 MWh/yr; adding a safety factor, the system was designed to supply 277 MWh/yr. In fact they used more at 351 MWh, and generated more at 418 MWh, delivering back to the grid more than they consumed by 66.73 MWh in the full year ending July 31, 2013, conclusive proof that it was truly Net-Zero.
Reducing the demand side took a lot of good green design, with extensive daylighting, very efficient mechanical systems and a clever cooling system:
In warm weather, water is cooled at night by a compressor-free cooling tower and stored in two 25,000-gallon underground tanks. During the day, the cool water is pumped into the pipes that run through the chilled beams. Three major air handling units pull in 100% outside air, then filter and dehumidify it. Air flowing across the beam is sufficient to cool the interior spaces.
The building complies with the "Right to Nature" requirement by avoiding the shading of any neighbours, and the Beauty + Spirit criterion by hiring a talented architect (EHDD) to design a building that fits. They don't automatically put energy first:
Early on, the design team chose to conform the building to the street grid - which is oriented 40 degrees off true north -- in order to be good neighbors and affirm that sustainable buildings don’t have to stand apart from their neighbors. The energy penalty associated with being off the solar axes was accepted in favor of a massing that contributed to the urban fabric of the community.
The Living Building Challenge is the toughest label in green building. The Net Zero Building Certification is much more approachable, almost an LBC Lite. That's one of the wonderful things about it; notwithstanding its name,
it actually is about more than just energy, that you have to do it right. Furthermore, you have to prove it.
Like the Passivhaus/ Passive House, the Net Zero Energy Building Certification has, in my opinion, a lousy name that doesn't truly reflect how differently the term is used. I am not sure co-opting a name in common use was the best approach. Nonetheless it is a great step forward in defining and refining the concept of a building that gives back more than it takes. I suspect that it is going to attract a wide following.
More on the The David and Lucile Packard Foundation.
In a post on the Net-Zero Energy Modern House I called Net Zero "a useless metric." It isn't any more; I have revised the earlier post accordingly. Net Zero Energy Building Certification really means something.