COVER STORY
Going Beyond
Net Zero Energy Buildings
Building industry today is going through a paradigm shift of performance, to reduce energy and carbon footprint. As per Dr Kath Williams, LEED Fellow and Principal, Kath Williams & Associate, USA, there is a growing realization towards combining whole building design with energy efficient technologies, to create Net Zero Energy Buildings (NZEB) and even going beyond.
In concept, an NZEB is a building with greatly reduced operational energy needs. In such a building, sufficient efficiency gains will have been made in such a way that the remaining portion of the building’s energy needs could be offset by renewable technologies.

The national government in the United States has taken the following actions:

• In the 2011 State of the Union Address, President Obama proposed a Better Buildings Initiative whose goal is to make all commercial buildings 20% more energy efficient by the end of the decade.
• Executive Order 13514 of October 2009 directs federal agencies, beginning in 2020, to achieve net-zero energy use in new construction and renovations by 2030.
• Energy Independence and Security Act of 2007 set a goal of net-zero energy use for all commercial buildings by 2030.
  • EISA 2007 further specified a net-zero energy target of 50% of U.S. commercial buildings by 2040 and a net-zero standard for 100% of new and existing commercial buildings by 2050.
  • The U.S. Department of Energy is developing measures that are designed to lead to cost-effective “NZEBs” by 2025,

Net Zero Goal and Definitions

  Throughout many project orientations, there were questions and misuse of the term “Net Zero” building”. Many designers offered suggestions about reaching net zero in regard to all resources, not just energy. Often, however, it is never clarified by owners, design and construction teams that they agreed with a goal – to design, build, and operate a NZEB (net-zero ENERGY building) OR a net-zero building that seeks to reach a balance in use of all resources, such as water and waste. For example, water experts who have designed net zero buildings often specify it should have:

• Rainwater storage sufficient to cover landscape and toilet/urinal flushing demand for three weeks
• Areas and runoff coefficients for all surfaces on the site, both indoors and outdoors, to properly size a storage tank and transfer system.
• Verification that using rainwater for interior applications is acceptable in local building codes
• Separate storage for rainwater and fire system backup because combining these into a single tank often creates new problems
• Pervious pavement in areas that will not provide practical rainwater catchment
• Clear understanding of the hydraulic properties of any proposed green roofs.
• How does it react to/shed rainwater? What are its irrigation needs?
• A water balance for the site with an understanding of how landscape plantings were designed. Are plants chosen for aesthetic reasons only, or were plants chosen with the assumption they should minimize need for added water? A more water-efficient landscape would reduce the volume of rainwater they’d need to store.
  • Permanent metering, recording, and educational displays showing potable and non-potable water flows.
  • Layout of kitchens and restrooms that minimizes pipe runs for hot water, and allows use of instant or small, localized water heaters. There are extensive opportunities with hot water during sustainable design decision-making.
  • WaterSense fixtures and faucets; 1.8 gpm faucets in kitchens (CalGreen-compliant); 1/8 gpf urinals
  • Pressure system that provides 35 psi at the toilet and urinal flushometer valves.
  • Peak instantaneous flow for these is around 25gpm.

  If the goal is to be a NZEB, there are four distinct definitions:

1. Net Zero Site Energy (produces at least as much energy on the site as the building uses; past projects have failed because on-site generation was redundant to conventional systems and added when funding was raised rather than being an integral part of the building systems
2. Net Zero Source Energy (produces or purchases renewable energy annually to match building use
3. Net Zero Energy Costs (renewable energy produced on site is sold to utility and is equal to energy purchased for the building from the utility
4. Net Zero Carbon Emissions (produces or purchases emissions-free renewable energy to offset emissions from all energy used annually in the building.

  To reiterate, often there is no information/data presented that leads everyone to understand definitions, strategies, or processes that will be used to reach a project’s publicly stated goal of “net zero.” A goal to produce an energy efficiency design (30% above ASHRAE 90.1-2007) gives no confidence that a project could achieve “net zero.” Strategies and technologies to reach net zero must be explored in detail from the early days of goal setting and design charrettes.

  The goal of LEED-Platinum, under the 2009 version, is extremely difficult to achieve with energy efficiency of only 30% above ASHRAE (equal to 10 LEED points, only half of energy points available). It will take diligent commitments by designers, landscape architects, and contractors to achieve the 80+ points necessary. Ideas and recommendations of industry leaders must clearly be incorporated into the design, looking clearly at near future opportunities that may not be readily available in the market today.

  Tips for charrettes regarding the Net-Zero Goals:

  • Definition should be clearly stated and agreed to by owner, design team, contractor, and facility managers who must operate and maintain for the long-term. Architects and engineers should clearly define design strategies to meet the agreed-upon Net Zero goal.
  • Energy model must be used early and often with the modeller being able to state what the modeling results were, what is the required, for example, on-site renewable to off-set the remaining portion of the building’s energy needs?
  • Throughout the design process, the design team must be able to launch into detail about every aspect of the design and how it relates to obtaining the goal.

  – For example, the daylighting design and the window size and selection was based on the balance between daylight and thermal load,then elaborate on that area. The design of the building should be integrated into the overall energy strategy and what effect each design element had on the overall net-zero design.

  - It is difficult to assume which energy efficiency strategies should be applied or what interior design model would be most acceptable until the entire teams has a clear understanding of why the building was designed the way it is, how the design helps achieve the net-zero goal and whether the net zero goal is achievable given project conditions.




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