ASHRAE LV-11-C020-2011 Application of ASHRAE Standards and Procedures in LEED-EB Certification.pdf

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1、Barry Abramson is Senior Vice President with Servidyne, Atlanta, GA. Lung-Sing Wong is Principal Engineer with Servidyne, Atlanta, GA. Application of ASHRAE Standards and Procedures in LEED-EB Certification Barry Abramson, PE Lung-Sing Wong, PE Member ASHRAE Member ASHRAE ABSTRACT The US Green Build

2、ing Councils LEED for Existing Buildings (LEED-EB) rating system relies upon several standards and procedures developed by ASHRAE. Some are well known, such as the ASHRAE Standard 62.1-2007 Ventilation Rate Procedure, but need to be applied under different circumstances than they have typically been

3、 in the past. Others, such as ASHRAE Procedures for Commercial Building Energy Audits, were lesser known several years ago, before LEED-EB was introduced. Such terms as “ASHRAE Level I” and “ASHRAE Level II” Energy Audits have now been popularized in the building industry. This paper will address th

4、e LEED-EB requirements that rely on these ASHRAE tools and resources and discuss the challenges to the engineer regarding proper application under various existing building scenarios. It will explain the pertinent concepts and definitions as presented in the ASHRAE resource documents, and present st

5、rategies for how these ASHRAE resources can most effectively be utilized in the LEED-EB certification process. INTRODUCTION The current version of the US Green Building Councils LEED for Existing Buildings rating system, LEED 2009 for Existing Buildings: Operations and Standard 62.1-2007 (ASHRAE 200

6、7), required for LEED-EB Indoor Environmental Quality Prerequisite 1. Because they both involve LEED-EB prerequisite requirements, these references must be used in every LEED-EB certification. Engineers providing technical consulting on LEED-EB certification projects must understand the ASHRAE sourc

7、e documents as well as the intent of the particular LEED requirements in order to properly apply ASHRAE guidance. ENERGY the incremental rate takes into account how each particular energy measure will affect the annual utility costs. Depending on the type of energy measure being analyzed and the loc

8、al utility rate structure, the difference between average and incremental rates can be substantial. The impact of using average versus incremental electric rates for several locations and types of measures is illustrated in Table 1 below. These rates were calculated for particular buildings and will

9、 vary depending on utility rate schedule and any third-party supplier contracts. Incremental rates for the various types of loads were calculated based on season, time-of-use, and the blended actual impact of usage and demand charges. For the Los Angeles building, as an example, the cost reduction o

10、f a measure saving energy at night only, such as after-hours scheduling controls, would actually be less than half the amount projected with the use of the average electric rate. Conversely, a chiller replacement project reducing cooling energy primarily in summer months and reducing peak demand wou

11、ld yield 40% more savings than would be anticipated using the average rate. Table 1. Average vs. Incremental Electric Rates ($/kWh) Los Angeles New York Chicago Atlanta Orlando Average Rate $0.15 $0.18 $0.11 $0.08 $0.11 Incremental 24-Hr Load Rate $0.10 $0.16 $0.09 $0.06 $0.11 Incremental Night Load

12、 Rate $0.07 $0.14 $0.08 $0.05 $0.10 Incremental Cooling Load Rate $0.21 $0.20 $0.12 $0.14 $0.14 Energy End Use Analysis. The Level I Walk-through Audit also includes a breakdown of annual energy consumption by end use. Analysis methods may vary but typically rely on simple spreadsheet calculations b

13、ased on broad assumptions, such as overall building lighting power density and typical hours of operation, annual cooling and heating load factors, etc. The results can be presented in tabular format or graphically, as shown in Figure 1. 2011 ASHRAE 165Figure 1 Energy end use analysis. Savings Measu

14、re Identification. The identification of potential savings measures is the centerpiece of an ASHRAE Level I Walk-through Audit. The measures are typically those that can be identified during a walk-through survey, without relying on in-depth investigation, data logging or detailed monitoring of exis

15、ting system performance. Both no-cost/low-cost operations and maintenance items, as well as capital retrofit projects, are included. The savings calculations and implementation cost estimates for capital projects are macro-level analyses. While the savings should be based on incremental utility rate

16、s as discussed above, the calculations will generally require some broad assumptions regarding system operating parameters, existing equipment efficiencies, etc. Cost estimates are budgetary and rely on unit pricing and industry-standard cost assumptions. ASHRAE Level II Energy Survey and Engineerin

17、g Analysis The Level I audit includes a recommendation for further study, if warranted. It may conclude that the next step should be retrocommissioning, if the opportunities for savings are focused on fine-tuning of existing systems operation and control; or it may call for a more in-depth energy au

18、dit. Procedures for Commercial Building Energy Audits (Cowan 2004) defines this more in-depth study as an ASHRAE Level II Energy Survey and Engineering Analysis. Building on the utility analysis and walk-through assessment in the Level I audit, the Level II effort includes a study and evaluation of

19、the existing energy-using equipment and systems, as well as more robust savings calculations and implementation cost estimates. More specific building system and equipment operational data is generally required in order to refine the inputs for the savings calculations performed in the Level I Audit

20、. The ASHRAE Level II Energy Audit report will present a description of the building systems and their current operating status, along with a detailed explanation of each recommended energy savings measure. Either path of further study, whether retrocommissioning or an ASHRAE Level II Energy Audit,

21、can attain credit points under LEED-EB Energy the area served by the system, including by zone occupancy type, and whether the space is currently occupied or unoccupied; the population of occupants by zone, with occupants in any vacant space calculated based on ASHRAE default values for occupant den

22、sity; total system air flow; system air flow diversity; which zone or zones are determined to be critical zones in terms of outside air requirements; and the minimum air flow to each zone, particularly the critical zone(s). Figure 2 2007UM_MZCalc Spreadsheet. 2011 ASHRAE 167Example Calculation The i

23、nput data for an example calculation is shown in Table 2. The subject air handling system is a VAV system serving a single floor in an office building. The floor is comprised of general office space, conference/meeting rooms, main entrance lobby, break rooms and vacant office space. Table 2. Example

24、 Input Data Component Input Value AHU system type VAV AHU design supply sir 18,000 cfm (9,000 L/s) Area served by AHU 20,000 ft2 (2,000 m2) Area currently cccupied 17,000 ft2 (1,700 m2) General office space 15,200 ft2 (1,520 m2) Conference/meeting rooms 1,200 ft2 (120 m2) Main entry lobby 400 ft2 (4

25、0 m2) Break rooms 200 ft2 (20 m2) Vacant office space 3,000 ft2 (300 m2) Current occupant count 75 People Total occupant count w/vacant space 90 People Air distribution type CS (ceiling supply cool air) Measured actual OA supply at minimum 3,500 cfm (1,750 L/s) The two key elements in the calculatio

26、n of required outside air are the critical zone and the assumed minimum supply air for the critical zone at the condition when the system requires the most outside air. In the example system, the critical zone is typically associated with the conference/meeting room space. Table 3 below shows the re

27、sults of the calculations for various assumptions of minimum supply air in the critical zone, using both Appendix A (2007UM_62MZCalc spreadsheet) and Table 6-3, where applicable. Table 3. Calculation Scenarios Critical Zone Minimum Supply Air % Appendix A System Ev Appendix A OA CFM (L/s) Required V

28、ot Table 6-3 System Ev Table 6-3 OA CFM (L/s) Required Vot 100% 0.94 1,762 (881) 1.00 1,658 (829) 50% 0.79 2,092 (1,046) 0.84 1,964 (982) 30% 0.58 2,825 (1,413) 0.63 2,605 (1,303) 25% 0.48 3,424 (1,712) N/A N/A Ev = Ventilation System Efficiency Vot = OA Intake Required for System Discussion As illu

29、strated in Table 3, the required outside air ranges by almost a factor of two based on the assumption of minimum supply air percent in the critical zone. The worst case outside air situation typically occurs when the critical zone is at minimum supply air flow while the rest of the zones and the sys

30、tem overall are at cooling design air flow. The ventilation efficiency (Ev) of the critical zone determines the ventilation efficiency of the system. The ventilation efficiency of the system then determines the system outside air requirement (Vot). Thus, identifying the critical zone and assessing t

31、he minimum supply air quantity in the critical zone at the time when the system is at maximum flow will establish the minimum outside air flow necessary for compliance with ASHRAE Standard 62.1-2007. The sensitivity of the calculation is illustrated in Figure 3 below. The outside air requirement inc

32、reases by approximately 20 percent when the critical zone minimum supply air assumption goes from 100 percent to 50 percent. The affect is more dramatic as the critical zone minimum supply air is reduced further. A good discussion of the factors influencing these calculations and the options for eng

33、ineering 168 ASHRAE Transactionsjudgment in establishing the minimum setpoint assumptions is presented in Stanke 2010. Figure 3 Sensitivity of required outside air calculations. CONCLUSION In both of the LEED-EB prerequisites that rely on ASHRAE reference documents discussed above, sound engineering

34、 judgment is required to properly apply ASHRAE guidance in meeting the intent of the LEED-EB requirements. In the case of LEED-EB Energy & Atmosphere Prerequisite 1, not only must the specified audit process be followed, but the appropriate level of effort must also be determined. In the case of LEE

35、D-EB Indoor Environmental Quality Prerequisite 1, engineering assumptions regarding ventilation system operating conditions can greatly impact the compliance calculations. Given the rigorous nature of the LEED certification review process, the engineering approach taken to demonstrate compliance, in

36、cluding the basis of the analysis and key assumptions, should be clearly presented in LEED submittal documentation. REFERENCES ASHRAE. 2007. ANSI/ASHRAE Standard 62.1-2007, Ventilation for Acceptable Indoor Air Quality. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Enginee

37、rs. ASHRAE. 2007. 62.1 Users Manual, ANSI/ASHRAE Standard 62.1-2007, Ventilation for Acceptable Indoor Air Quality. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers. Cowan, J., R. Pearson and I. Sud. 2004. Procedures for Commercial Building Energy Audits, ASHRAE Res

38、earch Project RP-669. Atlanta: American Society of Heating, Refrigerating and Air Conditioning Engineers. Stanke, D. 2010. Standard 62.1-2007 Dynamic Reset for Multiple-Zone Systems. ASHRAE Journal, 52(3): 22 35. USGBC. 2009. LEED Reference Guide for Green Building Operations and Maintenance, 2009 E

39、dition. Washington, DC: U.S. Green Building Council. USGBC. 2010. LEED 2009 for Existing Buildings: Operations and Maintenance Rating System (Updated July 2010). Washington, DC: U.S. Green Building Council. 1,0001,5002,0002,5003,0003,5004,0000% 20% 40% 60% 80% 100% 120%Critical Zone Primary SA %SystemOACfmRequiredAppendix A Table 6-3 2011 ASHRAE 169