1、Clark Bisel is a Senior Vice President of WSP Flack + Kurtz in San Francisco and a licensed professional engineer in over a dozen states. Zero Net Energy Buildings and Title 24 Energy Code Clark C. Bisel, PE ASHRAE member Preface - As a practitioner (and in agreement with the California Energy Commi
2、ssions net zero energy goals) I want to highlight issues and facilitate discussion associated with Title 24 and broader net zero energy building design issues. This paper is not directed at slowing the current zero net energy research and efforts, but rather to look forward at further refinements an
3、d improvements. Abstract Zero Net Energy has become a pressing issue in our industry, yet our current approach is not up to the regulatory task. We also need to clarify the definition of zero net energy buildings. There are several definitions of what it means (have differing metrics of site energy,
4、 source energy, emissions, and annual energy cost) and associated implied impacts - we need this consensus on the objective first. The current California Title 24 energy code /regulatory process is not comprehensive enough for net-zero-energy analysis: It includes a standard allowance for process en
5、ergy (without project-specific adaptation). The HVAC, domestic hot water and other energy systems in the codes modeling library is limited. The analysis rules are very constraining. The Title 24 performance analysis of systems is required to follow an existing approved (fixed) process as defined in
6、the Alternative Compliance Manual (ACM) - and using an approved computer program, DOE-2 based. This process does not allow one to account for performance of various non-traditional (likely more efficient) building solutions. Further, the defined systems available in the ACM often do not realisticall
7、y reflect how the systems are configured or are controlled / operated. For example, evaporative cooling is only allowed by the ACM for certain system types (it is allowed for central air systems, but not for fan coil schemes). Finally, one needs to begin an understanding of future impacts to Title 2
8、4 or the building industry in California. LV-11-C049406 ASHRAE Transactions2011. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions, Volume 117, Part 1. For personal use only. Additional reproduction, distribution, or tr
9、ansmission in either print or digital form is not permitted without ASHRAES prior written permission.WHY ZERO NET ENERGY BUILDINGS Climate change is a planetary issue that obliges mankind to reduce greenhouse gas generation. Much of the greenhouse gas generation is the result of energy consumption i
10、ncluding buildings, transportation, agriculture, manufacturing and industry. Buildings represent 40% of the US power consumption and are thus significant direct and indirect sources of greenhouse gas emissions. Many of these greenhouse gas sources are interactive with others sources. When we evaluat
11、e building energy consumption we endeavor to account for these interactions in our analysis. However, these models are rudimentary and miss many important interactions. In order to achieve the US greenhouse gas reduction goals and California Energy Commission (CEC) requirements it would be useful to
12、 comprehensively account for all issues in our analysis of zero net energy buildings including: All energy requirements (including process loads and user plug loads) Occupant transportation needs Waste stream energy losses Material manufacturing energy (including construction) Material transportatio
13、n energy (including construction) Environmental effects and the associated energy Other factors to understand the entire life cycle spectrum of building impacts THE DEFINITION OF ZERO NET ENERGY The term Zero Net Energy” needs to be more appropriately and comprehensively defined (the September 2009
14、ASHRAE Journal issue has an article that identifies four classifications). ASHRAE (as an organization) has previously defined net-zero-energy buildings as those which, on an annual basis, use no more energy from the utility grid than is provided by on-site renewable energy sources. A key term (and t
15、hus major flaw) in the above definition is on-site. This severely limits the real world application of the zero energy goals. The essence of this ASHRAE definition should be project-related energy generation, it needs be expanded to include more projects on-site energy opportunities may be overly re
16、strictive: Projects require an energy balance with their site, accommodated by a combination of number of floors (say less than 3) matched to available site area. If you have a low-rise building in a suburban location this may be possible. If you have an urban high-rise this definition is not possib
17、le. (This balance does not cover construction and transportation energy requirements on a life cycle basis. In other words, this less than 3 stories does not cover all the embodied energy along with operating energy). 2011 ASHRAE 407However, this position encourages sprawl and exacerbates growing tr
18、ansportation energy requirements. The California Energy Commission has concluded that transportation energy is 57% greater than building energy. Thus making more efficient buildings under this zero net energy definition may be counterproductive. Assuming that natural energy sources (solar and wind a
19、re identified by ASHRAE) are available for a building is a leap of faith. These resources are site specific and under best conditions may not be available. Further, it requires that these resources are continuously available to the building and one is not screened by neighbors. On one project in dow
20、ntown San Francisco, the building is a very short facility in a very tall neighborhood (akin to standing in a grove of redwood trees) there are no realistic solar or wind resources at the site period. A glaring limitation of Title 24 (currently) is that it explicitly does not allow on-site energy to
21、 be accounted for (for example photovoltaic systems are not considered at all). This ridiculous fact is an obvious requirement in the future. The net zero definition is often carefully worded, such that one needs to very carefully understand what is being claimed - process energy or unregulated user
22、 loads are often poorly considered or excluded from the users tailored description. Energy demand by definition is on an equal footing with energy supply. Thus energy conservation is as important as power generation options thus if it is more cost effective, then energy conservation will be pursued
23、until the marginal efficiency gain has a cost equal to the incremental cost of supply. SCOPE OF TITLE 24 Title 24 currently regulates energy directly and indirectly used in building heating, cooling, ventilation, interior lighting, exterior lighting, and service hot water. Title 24 (2008) excludes:
24、Plug and process loads which are significant (and may be the largest single component of building energy use). Data center buildings, for example, have inconsequential building energy use in comparison to computer equipment, yet the computer loads are completely unregulated and energy efficiency is
25、likely not a significant driver in the design process (compared to reliability, redundancy, and operational performance). These other issues are much more important to clients. I note that Title 24 (2008) begins to address process loads for refrigerated warehouses and future editions will incorporat
26、e requirements for additional building types. Water use attributable to the building even though the relationship between water use and energy has been documented. We note that a California Energy Commission report (CEC-700-2005-011, 2005 Integrated Energy Policy Report) discusses the significant st
27、ate-wide energy use associated with water use for treatment, conveyance, heating, desalination, and other. Water use is not regulated - irrigation is one area that has remarkable (and unregulated) water consumption needs. Water related measures are beginning to be included in the new Cal Green code
28、and new editions of Title 24. Vertical transportation energy Transportation energy (land planning). 408 ASHRAE TransactionsThese omissions mean that a significant portion of energy use associated with buildings is not included in the current definition of Title 24, yet to meet net zero energy goals
29、it has to be. While future code editions are beginning this process they need to be aggressive and comprehensive in addressing all aspects of building energy use. ANALYSIS TOOLS The performance approach for energy code compliance has become a standard approach in the industry. It has become (and see
30、ms that it will continue to be) the only viable way to analyze the myriad of potential situations solutions and also provide trade-offs. The performance analysis approach in the future may be the only way to demonstrate building zero net energy performance. The performance analysis of systems are re
31、quired to follow an existing approved (fixed) process as defined in the ACM - and using an approved computer program. This process does not allow one to account for performance of various non-traditional (more efficient) building solutions: Radiant heating and cooling systems Underfloor air distribu
32、tion systems Chilled beam systems (active and passive) On-site electrical generation systems Dedicated outdoor ventilation systems, where space thermal conditioning is (generally) independent of ventilation. Natural ventilation (perhaps only really effective in certain climates, but still a very act
33、ive issue but eliminated by Title 24) In the future these system approaches will become widespread. The defined systems available in DOE2 often do not realistically reflect how the systems are configured or are controlled and/or operated. For example, evaporative cooling is only allowed by the ACM f
34、or certain system types (it is allowed for central air systems, but not for fan coil schemes). We understand the intent of Title 24 is not to analyze exemplary performance, but to ensure minimal compliance. However, exemplary performance today will become the norm in the future. Performance analysis
35、 is the only vehicle seen as applicable to any zero net energy scenario and must address both building energy demand and also energy supply (on-site and off-site). We note that engineering practitioners are continually pushed by design architects to develop new system options and performance beyond
36、Title 24. Title 24 can be used on a comparative basis (for example, a recent proposed State of California project was required to be 30% below Title 24 and also the Savings by Design program is based on improvements beyond Title 24). 2011 ASHRAE 409HOW WILL A ZERO NET ENERGY REQUIREMENT DRIVE THE IN
37、DUSTRY? While it is difficult to predict how zero net energy requirements will impact the industry it is important to include this issue in any discussion. The impact may be profound: People will not build new buildings in California they will move to another state (another energy jurisdiction). Peo
38、ple will renovate existing buildings that have an established energy entitlement. As one extreme historic buildings, exempt from any energy code regulation, may be more attractive renovation opportunities. Incremental improvement goals for existing buildings would be an important step in this direct
39、ion. Title 24 only is applicable to the extent of Title 24 in the year the building was first permitted. Building owners will view the carbon reductions that they have achieved as an asset. They will seek to monetize this asset (such as carbon trading or sale of RECs). The California Energy Commissi
40、on may want to encourage (help develop) such opportunities outside of Title 24. Will Title 24 need to become a continuing certification process? The accomplishment of zero net energy is only realized in building operation it is not really a design related accomplishment. There currently is a signifi
41、cant disconnect between the two phases and designers rarely have any significant involvement during the operation phase of a building. Actual utility information is actually what is needed to confirm design information. Shouldnt building owner/operators submit documentation of their continued net ze
42、ro energy performance to a regulatory agency on an on-going basis? Title 24 was originally created as a design standard. Recently Title 24 has introduced the acceptance testing of some HVAC systems. In the future energy use will be publically disclosed, yet the designer is probably not involved and
43、the Title 24 design approval is a one-time (almost meaningless) event. CONCLUSION One hopefully sees the importance of meeting the net zero energy goal, yet the process of regulating this requirement (and seeing that it occurs) is full of land mines and fraught with questions. We need to earnestly address these issues and implement sweeping changes. 410 ASHRAE Transactions
