Net Zero Energy Buildings

Case Studies and Lessons Learned

Linda Reeder

• Éditeur: Routledge
• Année: 2016
• ISBN:
  9781317289982
• Édition: 1
• Sujet: Technology & Engineering
• Sous-sujet: Construction & Architectural Engineering

This book presents 18 in-depth case studies of net zero energy buildings—low-energy building that generate as much energy as they consume over the course of a year—for a range of project types, sizes, and U.S. climate zones. Each case study describes the owner's goals, the design and construction process, design strategies, measurement and verification activities and results, and project costs.

With a year or more of post-occupancy performance data and other project information, as well as lessons learned by project owners and developers, architects, engineers, energy modelers, constructors, and operators, each case study answers the questions:

• What were the challenges to achieving net zero energy performance, and how were these challenges overcome? How would stakeholders address these issues on future projects?

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• Are the occupants satisfied with the building? Do they find it comfortable? Is it easy to operate?

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• How can other projects benefit from the lessons learned on each project?

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• What would the owners, designers, and constructors do differently knowing what they know now?

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A final chapter aggregates processes to engage in and pitfalls to avoid when approaching the challenges peculiar to designing, constructing, and owning a net zero energy building.

By providing a wealth of comparable information, this book which will flatten the learning curve for designing, constructing, and owning this emerging building type and improve the effectiveness of architectural design and construction.

Part 1
Office buildings

Chapter 1
Bullitt Center

Seattle, Washington

The goal of the Bullitt Foundation in developing the six-story, 52,000-square-foot Bullitt Center was to create “the greenest building in the world” as a demonstration of what can be achieved, with the objective of transforming the way in which office buildings are designed, built, and operated. The construction of the core and shell of this Class A office building cost $18.5 million. The project is consistent with the Foundation’s mission “to safeguard the natural environment by promoting responsible human activities and sustainable communities in the Pacific Northwest.” Led by President and CEO Denis Hayes, the Foundation determined that the new building would be designed to achieve certification through the Living Building Challenge (LBC). Occupied in 2013, the building has performed as net positive energy for its first two years, generating more and using less energy than predicted. In 2014, the building’s energy use intensity (EUI) was 10.2 kBtu/ft²/year, compared to 67.3 kBtu/ft²/year for a typical office building. (See Box 1.1 for a project overview.)

Figure 1.1 The Bullitt Center is located in a dense urban neighborhood adjacent to a small triangular park that was remade as part of the project. The building’s PV array extends more than 20 feet beyond its perimeter. (© Nic Lehoux for the Bullitt Center)

The Bullitt Center (see Figure 1.1) is not only energy and carbon-neutral but also designed to be net zero water using ultra-filtered rainwater for all purposes—once approved by regulators—and composting toilets. Under the LBC, all elements of the program, called “imperatives,” are required to achieve Living certification. In addition, certification is based on the building’s actual performance over a year of occupancy, not on predicted performance. The 20 imperatives in the version of the LBC followed in this project were divided into six categories, or “petals:” Site, Water, Energy, Health, Materials, Equity, and Beauty. Net zero energy and net zero water are imperatives, and a list of chemicals and materials were excluded from use. In 2015, the Bullitt Center was the seventh building ever to receive Living Building certification, and the first multi-tenant, market-rate commercial building to receive the certification.

Features contributing to net zero water performance include rainwater harvesting, a gray water filtration system that includes a constructed wetlands on a third-floor roof terrace, and composting toilets. The fire sprinkler system uses pressurized city water and is an exception to the net zero water imperative. Although the building is permitted as its own water district to allow the use of treated rainwater, the approval process permitting the building manager to operate it had not been received more than two years after initial occupancy.

Several project team members noted that the net zero water component and identifying materials compliant with the Living Building Challenge requirements were in many ways greater challenges than achieving net zero energy. “Trying to eliminate more than 350 toxic materials from about 1,000 building components involved two full person-years of work,” said Hayes. “However, we have posted all our choices on our website, so future Living Building developers can stand on our shoulders and have a much easier task.”

Box 1.1: Project overview

IECC climate zone	4C
Latitude	47.61°N
Context	Urban
Size	51,990 gross ft^2 (4,830 m^2) 50,000 ft^2 conditioned area (4,645 m^2) 44,766 ft^2 net rentable area (4,159 m^2)
Building footprint	10,076 ft^2 (936 m^2)
Height	6 stories
Program	Class A Office
Occupants	145 FTE, plus about 3,000 visitors annually
Annual hours occupied	2,600
Energy use intensity (2014)	EUI: 10.2 kBtu/ft^2/year (32.2 kWh/m^2/year) Net EUI: –6 kBtu/ft^2/year (–19 kWh/m^2/year)
National median EUI for offices^1	67.3 kBtu/ft^2/year (212.5 kWh/m^2/year)
Demand-side savings vs. ASHRAE Standard 90.1–2007	75%
Certifications	Living Building Challenge (version 2.0)

1 Energy Star Portfolio Manager benchmark for site energy use intensity

The basement houses many of the building systems, including the 56,000-gallon cistern for rainwater collection and 10 large composting units for the composting toilet system. The structure of the basement and lower two floors is concrete (see Figure 1.2). To reduce the embodied energy of the building and in keeping with vernacular architecture of the region, the top four stories are timber, framed with wood decking made from 2 × 6s on edge. The floors have concrete topping slabs for thermal mass. All wood is FSC (Forest Stewardship Council) certified. For bracing against lateral loads, the bathroom core is concrete on the lower floors and there is steel bracing on the timber-framed floors. The building, which covers 98 percent of the site, has no car parking spaces. There is a bike parking room and showers for occupants commuting by bike or on foot. The building is easily accessible by public transportation.

The ground floor includes a two-story lobby and exhibition space with educational displays about the building’s design and performance, as well as a classroom area. The Bullitt Center had more than 6,000 visitors in its first two years of operation. The second-floor mezzanine and third through sixth floors are tenant spaces.

Figure 1.2 The structure of the lower two floors is concrete (Section B). The upper four floors are set back to maximize daylight penetration (Level 3 Plan). (The Miller Hull Partnership)

In addition to meeting environmental goals, the building also had to attract tenants both for financial reasons and to demonstrate replicability. The Foundation occupies just 10 percent of the rental area. During the first year, the building averaged around 50 percent occupancy. About two years after opening, the last tenant space was leased out. Tenants include firms that were on the project team and the organization that administers the LBC. Rent is competitive with Class A office space in Seattle, but the building is located outside of the central business district. Tenants must commit to meeting water and energy conservation targets, and tenant fit-outs must comply with the LBC requirements for materials.

Box 1.2: Project team

Owner	Bullitt Foundation
Developer	Point32
Architect	The Miller Hull Partnership
Mechanical/Electrical Engineer and Energy Modeling	PAE Consulting Engineers
Solar PV Design	Solar Design Associates
Structural Engineer	DCI Engineers
Water Systems Engineer	2020 Engineering
Civil Engineer	Springline Design
Landscape Architect	Berger Partnership
Envelope Consultant	RDH Building Envelope Consultant
Daylighting Design Support	Integrated Design Lab, University of Washington
Geotechnical Engineer	Terracon
General Contractor	Schuchart

Design and construction process

Developer Point32 was involved early in the process, helping the Foundation evaluate the project’s feasibility and selecting the site (Weber Thomson Architects completed a site feasibility study) and project team (see Box 1.2). The site in Seattle’s Capitol Hill neighborhood is on a busy thoroughfare near downtown, and the zoning regulations governing height limitations and existing surrounding buildings made maintaining solar access a good gamble. Point32 also worked with city leaders to develop and enact the Living Building Pilot Program, an ordinance created to promote the development of buildings that meet the Living Building Challenge by allowing the modification of regulations that discourage buildings from meeting the LBC. A Technical Advisory Group was established to review the design and requests. The Bullitt Center would not have been able to achieve LBC certification without the Living Building Pilot Program and the cooperation of the city.

The contributions of many people who participated in the design process but were not part of the design team were essential, said Jim Hanford, AIA, Sustainability Architect for The Miller Hull Partnership. A large group of local energy and green building experts participated in early design charrettes. Among these were Christopher Meek, AIA, of the University of Washington’s (UW’s) Integrated Design Lab, who provided expertise on daylighting and visual comfort throughout the process, and UW’s Building Performance Consultant Robert B. Peña. The City’s utility company, Seattle City Light, also provided...