Two net zero energy building (NZEB) projects have been making the rounds through various news media outlets and the blogosphere recently. This is to be expected from something that is expected to grow to over $1 trillion/year industry over the next two decades. Developers, contractors, architects, engineers and suppliers are all trying to establish themselves as leaders and innovators in the NZEB industry. NZEBs are buildings that have zero net energy consumption and zero carbon emissions annually. Electricity is generated onsite using renewable energy sources typically gathered onsite such as wind, solar or geothermal.
The first of these projects is DPR Construction’s regional office located in Phoenix, AZ. This 16,533 SF renovation of the former Castle Boutique Megastore recently received NZEB certification by the International Living Future Institute through their Living Building Challenge. The DPR Phoenix building is the largest building certified through the program to date. Although the building has been occupied since October 2011 it just received certification this past May due to requirements that energy bills for a continuous 12-month period be provided in order to prove its zero net energy consumption.
The second project is the LPL Financial at La Jolla Commons in San Diego, CA being developed as part of a joint venture led by Hines, a privately owned, international real estate firm. This 13-story, 415,000 SF Class A office tower is being touted as the nation’s largest net zero energy commercial office building. Construction on the new building began in April 2012 and the project is scheduled for completion sometime mid-2014. LPL Financial, LLC will be leasing the entire building.
Both projects were fairly ambitious with one requiring renovation of an existing building built in around 1972 and located in a city where the daily average high temperatures during the summer months are in excess of 100 degrees. The other required planning and funding a Class A office building to meet the needs and requirements of a pre-established tenant. Taking a closer look at key components of both projects such as the amount of energy generation and consumption, green/sustainable building elements, construction costs and the methods of renewable onsite energy generation it’s clear that not every NZEB is built the same.
The LPL Financial at La Jolla Commons is expected to generate approximately 5 million kWh of electricity annually while consuming approximately 4 million kWh. The DPR Phoenix building was designed to consume 138,371 kWh annually. Actual energy use was 129,589 kWh while onsite energy generation was 142,844 kWh. The LPL Financial building is being built to consume 41.5 kBtu/SF a year while the DPR Phoenix building consumes 28.85 kBtu/SF a year. So while the LPL Financial building is expected to use only 80 percent of the energy it generates compared to DPR Phoenix’s 91 percent, the DPR Phoenix is using 12.65 kBtu/SF less per year.
Green/Sustainable Building Elements
A number of elements were used on both projects in order to reduce energy consumption. The LPL Financial building will incorporate double-pane glass curtain walls with low-emissivity coatings and an under floor air distribution that requires less energy to cool the building. The building will also utilize reclaimed water for its cooling tower system and wastewater. The LPL Financial project was pre-certified as LEED Silver and could potentially achieve LEED Platinum once the building is completed.
The DPR office utilizes a number innovative sustainability features to help cool the building in the Phoenix heat. There are 87 windows operated by an energy monitoring system to open and close them based on the relative indoor and outdoor temperatures. An 87-foot zinc clad solar chimney creates a convection current that draws cool air into the building and releases hot air out. These two features work with shower towers to regulate building temperatures by acting as an evaporative cooler. The building also features 12 of Big Ass Fans’ eight-foot Isis fans for air distribution and 82 Soalartubes that meets practically all of the building’s daytime lighting needs. Another neat energy saving feature is a “vampire” shut-off switch that can be activated by the last person leaving the building and kills power to all power plugs so any electrical device plugged in won’t be wasting electricity. The DPR building received LEED-NC Platinum certification.
Construction costs for the LPL Financial at La Jolla Commons are estimated to be $265/SF which includes the core and shell along with tenant improvements. The DPR Phoenix renovation project cost $3,762,000 which equates to roughly $228/SF. Keep in mind that DPR Construction served as the general contractor for their own office renovation.
Renewable Onsite Energy Generation
Electricity for the DPR Phoenix building is generated onsite using a 78.96 kW direct current photovoltaic array along with a solar thermal hot water system to generate all the power needed to run the building. The photovoltaic system consists of 326 Kyocera 235Wdc solar panels in two configurations installed on top of structural parking canopies located onsite. The system is tied into the grid and energy production and consumption is measured throughout the year. The solar thermal system is comprised of a 4,500W Rheem, closed-loop glycol system with an 85-gallon capacity tank. This system provides hot water and heat in the winter to the building.
The LPL Financial building will use three fuel cells sourced from Bloom Energy to generate onsite electricity. These Bloom Boxes converts natural gas into electricity through a non-combustive, electro-chemical process. The system will initially run on methane gas but eventually is expected to run on biogas. Bloom Energy fuel cells do produce CO2 when natural gas is used to generate electricity it is less than the amount produced from coal-fired and natural gas plants. When biogas is used the Bloom Boxes are 100 percent carbon neutral. To reach carbon neutrality it offset the CO2 produced by purchasing directed biogas to be inserted into the pipeline to match natural methane used onsite.
Not All NZEBs Are Created Equal
By comparing these two projects it’s clear that designating a building as net zero covers a very broad spectrum. The argument has already been made by other that calling the LPL Financial building a NZEB is a bit of a stretch. Unlike the DPR building, it wouldn’t even qualify for NZEB certification under the International Living Future Institute (ILFI) due to the fact that 100 percent of the building’s energy needs must be supplied by onsite renewable energy and ‘green tags’ or ‘green power’ purchases are not recognized compliant paths. The ILFI also has an imperative that requires buildings be constructed on previously developed sites such as greyfields or brownfields. For example, if you built a new building that was completely off the grid and all electricity was produced through onsite solar and wind energy but was on an undeveloped tract of land it wouldn’t qualify based on their requirements.
That’s not enough to say that the LPL Financial project won’t be net zero. The U.S. Department of Energy’s National Renewable Energy Laboratory has a less stringent classification system that takes into account various onsite and offsite supply options. Based on this classification system they are using the lowest valued supply option because they are purchasing their renewable energy which would result in a classification of NZEB:D which is the lowest classification available. This again may be cause for debate since even NZEB:D classification require that “on-site renewable strategies are used to the maximum extent feasible.” They could qualify as a source and emissions NZEB depending on the source and quantity of renewable energy purchased.
At the end of the day the DPR Phoenix office is clearly the better example of a true NZEB but the LPL Financial project is not without its merits. Hines goal was to create a Class A office building first and they wanted to make it net zero without have to make major design changes. In addition, they had to do all of this while meeting the demands and goals of a client that had already signed a lease to occupy the building. Perhaps Hines will take the lessons learned from this project and apply it to their next net zero energy project and incorporate more sustainable features and energy generation through onsite renewable sources. They are currently looking into renovating the 600,000+ SF Columbia Square office building in Washington, D.C. into a NZEB.