ASHRAE Standard : Ventilation Rate Procedure

Transcription

1 engineers newsletter live Course Outline ASHE Standard : Ventilation Rate Procedure This presentation covers the Ventilation Rate Procedure for calculating zone and system ventilation airflow, which still exists in the standard today. As a prerequisite to obtain LEED certification, this program will help viewers understand the requirements of Standard 62.1 to better enable you to work with and satisfy your customers with respect to building ventilation. After attending this event, you will be able to: 1. Summarize the ASHE ventilation 2. Interpret ventilation rates for people- and building-related contaminants 3. Determine the required ventilation for individual zones based on space 4. Calculate the overall minimum outdoor air intake based on system Program Outline: Use 3-zone example from Dennis PowerPoint presentations 1) Introduction a) History - how are addendum 62n and related b) Relationship to LEED 2.2 c) Clarify the focus on Ventilation Rate Procedure, not IAQ Procedure 2) Explain separate of zone calculations and system calculations in ) Zone calculations a) Explain change to ventilation rates b) Explain average population calculation c) Explain air distribution effectiveness (Ez) and zone outdoor airflow i) Show example calculations ii) Compare to 2001 version (Ev was not prescriptive) iii) Compare various systems (overhead, underfloor, etc.) iv) LEED 2.1 credit interpretation request 4) System calculations a) Introduce different system types b) Single-zone system review steps c) 100% OA system review steps d) Multiple-space, recirculating system review steps

2 engineers newsletter live Presenter Biographies August 2010 ASHE Standard : Ventilation Rate Procedure Brian Fiegen Global systems application leader Trane Brian currently leads the Applications Engineering, Systems Engineering, and C.D.S. groups within Trane. Brian joined Trane in 1983, and has held a number of marketing and management positions throughout his career. He has been involved with product development and promotion of air handling and distribution products, systems, and controls throughout much of that time. Brian is deeply involved in managing Trane s position on key industry issues such as IAQ and sustainable construction. Brian earned his BSME from South Dakota School of Mines and Technology in Rapid City, SD. John Murphy senior applications engineer Trane John has been with Trane since His primary responsibility as an applications engineer is to aid design engineers and Trane sales personnel in the proper design and application of HVAC systems. He recently authored two Trane application manuals titled Air-to-Air Energy Recovery in HVAC Systems and Dehumidification in HVAC Systems, as well as an article for the ASHE Journal titled Dehumidification Performance of HVAC Systems. He also is the primary author of the recently revised Trane Air Conditioning Clinics, a series of training manuals on HVAC fundamentals. John is a member of ASHE and a member of that society s Moisture Management in Buildings technical committee. Dennis Stanke staff applications engineer Trane With a BSME from the University of Wisconsin, Dennis joined Trane in 1973, as a controls development engineer. He is now a Staff Applications Engineer specializing in airside systems including controls, ventilation, indoor air quality, and dehumidification. He has written numerous applications manuals, published many technical articles in industry magazines, and is a regular presenter in the Trane Engineers Newsletter Live program series. An ASHE Fellow, he currently serves as Chairman of SSPC189.1, the ASHE committee responsible for Standard 189.1, Design of High-Performance Green Buildings. He recently served as Chairman for SSPC62.1, the ASHE committee responsible for Standard 62.1, Ventilation for Acceptable Indoor Air Quality, and he served on the USGBC LEED Technical Advisory Group for Indoor Environmental Quality (the LEED EQ TAG).

3 ASHE Std : Ventilation Rate Procedure ASHE Std : Ventilation Rate Procedure an Engineers Newsletter Live series 2010 Ingersoll-Rand. All rights reserved Trane is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-aia members available on request. This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. 1

4 ASHE Std : Ventilation Rate Procedure Copyrighted Materials This presentation is protected by US and International copyright laws. Reproduction, distribution, display, and use of the presentation without written permission of Trane or American Standard is prohibited. AIA continuing education Learning Objectives Participants will be able to: Interpret ventilation rates for peopleand building-related contaminants Determine the required ventilation for individual zones based on space type Calculate the overall minimum outdoor air intake based on system type using the Ventilation Rate Procedure for acceptable indoor air quality as defined in ASHE Standard

5 ASHE Std : Ventilation Rate Procedure Today s Topics History Ventilation Rate Procedure Zone calculations System calculations Dynamic reset 2005 American Standard Inc. Answers to your questions Today s Presenters Dennis Stanke staff applications engineer Brian Fiegen manager, applications engineering John Murphy applications engineer 3

6 ASHE Std : Ventilation Rate Procedure ASHE Standard 62.1 Chronology in Brief lower rates a little change a little more change first issued higher rates incorporates addenda, changes ventilation rates Minimum standard with mandatory language and continuous revisions ASHE Standard 62.1 Why Care? Basis for many codes Adopted in whole or in part Sometimes more stringent than codes Helps establish standard of care for designer conduct (legally defensible) Prerequisite for LEED credits Must meet Std to qualify for any LEED-NC v2.2 credits 4

7 ASHE Std : Ventilation Rate Procedure how much outdoor air? ASHE Std 62.1 Says Comply with general requirements To minimize generation of indoor contaminants To minimize introduction of outdoor contaminants Comply with ventilation requirements To dilute and remove indoor contaminants ASHE Std Section 6.0 IAQ Procedure Must ventilate to achieve specific concentration targets for contaminants of concern It s performance-based Ventilation Rate Procedure Dictates rates and procedures based on typical spaces It s prescriptive 5

8 ASHE Std : Ventilation Rate Procedure ASHE Std , Section 6.2 Ventilation Rate Procedure Zone calculations Determine breathing-zone outdoor airflow for each zone System calculations Calculate outdoor-air intake flow for entire system Zone Calculations ASHE Standard ventilation requirements 2010 Ingersoll-Rand. All rights reserved 6

9 ASHE Std : Ventilation Rate Procedure section Zone Calculations 1. Calculate breathing-zone outdoor airflow, using Table 6-1 rates Vbz = Rp Pz + Ra Az 2. Determine zone air distribution effectiveness, Ez Look up Ez in Table Calculate zone outdoor airflow Voz = Vbz/Ez table 6-1 Minimum Ventilation Rates Rp Ra Rp Ra Occupancy category cfm/p cfm/ft² cfm/p cfm/ft² Office Classroom (ages 5-8) Lecture classroom Retail sales Auditorium Std prescribes both per-person AND per-area rates 7

10 ASHE Std : Ventilation Rate Procedure section Zone Calculations 1. Calculate breathing-zone outdoor airflow, using Table 6-1 rates Vbz = Rp Pz + Ra Az where, Rp = outdoor airflow rate required per person, in cfm/person Ra = outdoor airflow rate required per unit area, in cfm/ft² Pz = zone population largest expected qty, in quantity of people Az = zone floor area net occupiable area, in ft² section zone calculations Breathing-Zone OA Flow Example: Office space Rp = 5 cfm/person Ra = 0.06 cfm/ft² Pz = 5 people Az = 1000 ft² Vbz = Rp Pz + Ra Az = = 25 cfm + 60 cfm = 85 cfm Vbz 85 cfm breathing zone 8

11 ASHE Std : Ventilation Rate Procedure section zone calculations Breathing-Zone OA Flow Example: Conference room Rp = 5 cfm/person Ra = 0.06 cfm/ft² Pz = 17 people Az = 1000 ft² Vbz = Rp Pz + Ra Az = = 85 cfm + 60 cfm = 145 cfm Vbz 145 cfm breathing zone vs versions Comparison Occupancy category Vbz Vbz (default 2004 density, p/1000 ft²) cfm cfm Office (5 p) Conference room (17 p) Classroom (ages 5-8) (25 p) Lecture classroom (65 p) Retail sales (20 p) Auditorium (150 p) Most OA flow rates drop a little some, a lot! 9

12 ASHE Std : Ventilation Rate Procedure zone ventilation rates Relationship to Codes When Standard rates are lower than building code rates, how should we design? Comply with Standard, ignore code? (Not recommended) Comply with code, ignore Standard 62? (Not recommended) Comply with code, request variance when appropriate? (Good approach, but depends on authority having jurisdiction) section Short-Term Conditions May use Equation 6-9 to find averaging time and adjust design for short-term conditions T = 3 v/vbz where, v = zone volume, ft³ Vbz = breathing-zone OA flow, in cfm 10

13 ASHE Std : Ventilation Rate Procedure design for fluctuating occupancy Example: Office Space Example office space: Pz = 5 people Az = 1,000 ft² ceiling = 10 ft v = 10,000 ft³ Based on peak population: Vbz = Rp Pz + Ra Az = ,000 = 25 cfm + 60 cfm = 85 cfm Averaging time period: T = 3 v / Vbz = 3 10,000 / 85 = 353 minutes 6 hours design for fluctuating occupancy Example: Office Space 16 zone population, Pz Pz = 5 Highest Pz averaged over a 6-hr period (T) is 3.8 people 0 midnight 6 a.m. noon 6 p.m. midnight 11

14 ASHE Std : Ventilation Rate Procedure design for fluctuating occupancy Example: Office Space Example office space: Pz = 5 people Pz = 3.8 people Az = 1000 ft² Based on peak population: Vbz = Rp Pz + Ra Az = = 25 cfm + 60 cfm = 85 cfm Based on average population: Vbz = Rp Pz + Ra Az = = 19 cfm + 60 cfm = 79 cfm design for fluctuating occupancy Example: Conference Room Example conference room: Pz = 17 people Az = 1,000 ft² ceiling = 10 ft v = 10,000 ft³ Based on peak population: Vbz = Rp Pz + Ra Az = ,000 = 85 cfm + 60 cfm = 145 cfm Averaging time period: T = 3 v / Vbz = 3 10,000 / 145 = 207 minutes 4 hours 12

15 ASHE Std : Ventilation Rate Procedure design for fluctuating occupancy Example: Conference Room 16 Pz = 17 zone population, Pz Highest Pz averaged over a 4-hr period (T) is 9.75 people 0 midnight 6 a.m. noon 6 p.m. midnight design for fluctuating occupancy Example: Conference Room Example conference room: Pz = 17 people Pz = 9.75 people Az = 1000 ft² Based on peak population: Vbz = Rp Pz + Ra Az = = 85 cfm + 60 cfm = 145 cfm Based on average population: Vbz = Rp Pz + Ra Az = = 49 cfm + 60 cfm = 109 cfm 13

16 ASHE Std : Ventilation Rate Procedure section Zone Calculations 1. Calculate breathing-zone outdoor airflow, using Table 6-1 rates Vbz = Rp Pz + Ra Az 2. Determine zone air distribution effectiveness, Ez Look up Ez in Table Calculate zone outdoor airflow Voz = Vbz/Ez Find zone air distribution effectiveness (Ez) based on air distribution configuration Air distribution configuration Ez Ceiling supply cool, 1.0 ceiling or floor return Ceiling supply hot (>T space + 15 F), 0.8 ceiling return Ceiling supply warm (<T space + 15 F), 1.0 ceiling return Floor supply cool (mix to 4.5 ft), 1.0 ceiling return Floor supply warm, 0.7 ceiling return Excerpt from Table

17 ASHE Std : Ventilation Rate Procedure section zone calculations Zone Outdoor Airflow Example: Office space with overhead cooling (Ez = 1.0) Voz = Vbz/Ez = 85/1.0 = 85 cfm 0 cfm 85 cfm Voz Vbz 85 cfm breathing zone section zone calculations Zone Outdoor Airflow Example: Office space with overhead heating (Ez = 0.8) Voz = Vbz/Ez = 85/0.8 = 106 cfm 21 cfm 106 cfm Voz Vbz 85 cfm breathing zone 15

18 ASHE Std : Ventilation Rate Procedure Supply Return SA temperature Ez Voz Ceiling Ceiling or floor Cool Ceiling Floor Warm Ceiling Ceiling Warm (< T space + 15 F) Ceiling Ceiling Hot (> T space + 15 F) Floor Ceiling Cool (underfloor air distr) Floor Ceiling Cool (displacement) Floor Ceiling Warm Floor Floor Warm Makeup air drawn in, return/exhaust at opposite side of room Makeup air drawn in, return/exhaust near supply vs versions Comparison versions Section discussed impact of air distribution on ventilation effectiveness, but did not provide default values Most designers used Ez = Provides default values for (ventilation) effectiveness, based on air distribution configuration 16

19 ASHE Std : Ventilation Rate Procedure LEED-NC Version 2.1 EQ Credit 2, Ventilation Effectiveness and ASHE Standard 129 Rating document cites it but reference guide says it s not appropriate for most field applications Credit Interpretation Ruling (CIR) dated 7-July-2004 ADPI 80% ASHE Fundamentals Handbook Ez 0.9 ASHE Std : Table 6-2 second public review draft LEED-NC Version 2.2 EQ Credit 2, Increased Ventilation Replaces ventilation effectiveness credit with: Increase breathing zone outdoor air ventilation rates [Vbz] to all occupied spaces by at least 30% above the minimum rates required by ASHE Standard

20 ASHE Std : Ventilation Rate Procedure section Zone Calculations 1. Calculate breathing-zone outdoor airflow, using Table 6-1 rates Vbz = Rp Pz + Ra Az 2. Determine zone air distribution effectiveness, Ez Look up Ez in Table Calculate zone outdoor airflow Voz = Vbz/Ez System Calculations (One path for ventilation air) ASHE Standard ventilation requirements 18

21 ASHE Std : Ventilation Rate Procedure System Calculations Single-zone systems One air handler serving one zone 100% outdoor air systems One air handler serving many zones (no recirculation) Multiple-zone recirculating systems One air handler serving many zones (with recirculation) section Single-Zone Systems Find the required outdoor-air intake flow for the system (Vot): Vot = Voz packaged rooftop unit OA Vot = 85 cfm EA SA Voz = 85 cfm zone 19

22 ASHE Std : Ventilation Rate Procedure section % OA Systems Find the required outdoor-air intake flow for the system (Vot) Vot = Voz EA Vot dedicated OA unit = Voz = = 1200 cfm OA Vot = 1200 cfm fan-coil SA CA zone 1 Voz = 300 SA CA zone 2 Voz = 400 SA CA zone 3 Voz = 500 section Multiple-Zone Recirculating Can t deliver OA with 100% efficiency because some excess OA exhausts air handler OA Some excess (unused) OA leaves building EA zone 1 OVER- VENTILATED zone 2 PROPERLY VENTILATED zone 3 OVER- VENTILATED 20

23 ASHE Std : Ventilation Rate Procedure multiple-zone recirculating systems System Ventilation Efficiency Find system ventilation efficiency (Ev): Either use... Table 6-3, default Ev method OR Appendix A, calculated Ev method example Single-Path System air handler OA EA zone 1 Voz = 300 zone 2 Voz = 400 zone 3 Voz =

24 ASHE Std : Ventilation Rate Procedure default Ev method Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zp or Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) default Ev method Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zp or Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) 22

25 ASHE Std : Ventilation Rate Procedure default Ev example Single-Path System Zp = Voz / Vpz In systems, use minimum expected primary airflow (Vpzm) air handler OA EA zone 1 Vpz = 2600 Vpzm= 650 Voz = 300 zone 2 Vpz = 3400 Vpzm= 850 Voz = 400 zone 3 Vpz = 4000 Vpzm= 1000 Voz = 500 Zp = 0.46 Zp = 0.47 Zp = 0.50 default Ev method Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zp or Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) 23

26 ASHE Std : Ventilation Rate Procedure default Ev example Single-Path System Find the system s uncorrected outdoor air intake (Vou): Vou = D (Rp Pz) + (Ra Az) D = Ps / Pz where, D = occupant diversity Ps = peak system population Pz = sum of design zone populations default Ev example Occupant Diversity D= Ps / Pz = 80/122 = 0.66 air handler OA EA Pz = 122 zone 1 zone 2 zone 3 Pz = 20 Pz = 32 Pz = 70 Ps = 80 people 24

27 ASHE Std : Ventilation Rate Procedure default Ev example Uncorrected OA Intake zone Rp Pz Ra Az = = = = = = 150 (Rp Pz) = 610 (Ra Az) = 590 Vou = D (Rp Pz) + (Ra Az) = = 990 cfm default Ev method Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zp or Zd) 5. Uncorrected outdoor air intake (Vou) 2010Ingersoll-Rand American Standard All All rights reserved 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) 25

28 ASHE Std : Ventilation Rate Procedure default Ev example Single-Path System To find Ev from Table 6-3, use the largest Zp value among the zones served (Okay to interpolate) Table 6-3 excerpt max Zp Ev max Zp = 0.50 Ev= > 0.55 use Appendix A default Ev method Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zp or Zd) 5. Uncorrected outdoor air intake (Vou) 2010Ingersoll-Rand American Standard All All rights reserved 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) 26

29 ASHE Std : Ventilation Rate Procedure default Ev example Single-Path System Vot = Vou / Ev = 990 / 0.65 = 1520 cfm air handler Vot = 1520 cfm OA EA zone 1 zone 2 zone 3 Voz = 300 Voz = 400 Voz = 500 multiple-zone recirculating systems System Ventilation Efficiency Find system ventilation efficiency (Ev): Either use... Table 6-3, default Ev method OR Appendix A, calculated Ev method 27

30 ASHE Std : Ventilation Rate Procedure calculated Ev method* Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) *One ventilation-air path calculated Ev method* Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) *One ventilation-air path 28

31 ASHE Std : Ventilation Rate Procedure calculated Ev example Single-Path System For single-path systems, Zd = Zp Zd = Voz / Vdzm air handler OA EA zone 1 Vdz = 2600 Vdzm= 650 Voz = 300 zone 2 Vdz = 3400 Vdzm= 850 Voz = 400 zone 3 Vdz = 4000 Vdzm= 1000 Voz = 500 Zd = 0.46 Zd = 0.47 Zd = 0.50 calculated Ev method* Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) *One ventilation-air path 29

32 ASHE Std : Ventilation Rate Procedure calculated Ev example Uncorrected OA Intake zone Rp Pz Ra Az = = = = = = 150 (Rp Pz) = 610 (Ra Az) = 590 Vou = D (Rp Pz) + (Ra Az) = = 990 cfm calculated Ev method* Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) *One ventilation-air path 30

33 ASHE Std : Ventilation Rate Procedure calculated Ev method Single Recirculation Path 6a. Average OA fraction (Xs) Xs = Vou / Vps 6b. Zone ventilation efficiency (Evz) Evz = 1 + Xs Zd 6c. System ventilation efficiency (Ev) Ev = smallest Evz calculated Ev example Single-Path System Find system primary airflow (Vps): Vps = LDF Vpz LDF = block load / peak loads where, LDF = cooling load diversity factor Vpz = sum of zone peak primary airflows 31

34 ASHE Std : Ventilation Rate Procedure calculated Ev example Single-Path System Vps = LDF Vpz = ,000 = 5,000 cfm air handler Vps = 5000 cfm OA EA Vpz = 10,000 cfm zone 1 zone 2 zone 3 Vpz = 2600 Vpz = 3400 Vpz = 4000 calculated Ev example Single-Path System 6a. Calculate average OA fraction (Xs) for the system: Xs = Vou / Vps = 990 / 5000 =

35 ASHE Std : Ventilation Rate Procedure calculated Ev example Single-Path System 6b. For each zone, determine zone ventilation efficiency (Evz): Evz = 1 + Xs Zd (for single-path systems) zone Xs Zd Evz calculated Ev example Single-Path System 6c. Find system ventilation efficiency (Ev) Ev = smallest Evz = 0.70 zone Xs Zd Evz

36 ASHE Std : Ventilation Rate Procedure calculated Ev method* Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) *One ventilation-air path calculated Ev example Single-Path System Vot = Vou / Ev = 990 / 0.70 = 1410 cfm air handler Vot = 1410 cfm OA EA zone 1 zone 2 zone 3 Voz = 300 Voz = 400 Voz =

37 ASHE Std : Ventilation Rate Procedure vs. previous versions Single-Path System Std version Vou Ev method Vot n/a n/a n/a Table Appendix A 1410 Credit allowed for population diversity Appendix A generally results in lower Vot than Table 6-3 Comparison uses equivalent zone outdoor airflows (Voz), based on ASHE Std heating vs. cooling Single-Path System Ev method Mode Ev Vot Table 6-3 Cooling Heating n/a n/a Appendix A Cooling Heating Ez = 0.8 in heating, but Xs is higher because Vps drops 35

38 ASHE Std : Ventilation Rate Procedure System Calculations (Primary and secondary paths for ventilation air) ASHE Standard ventilation requirements 2010 Ingersoll-Rand. All rights reserved multiple-zone recirculating systems Two Ventilation-Air Paths Dual fan, dual duct One AHU for central primary recirculation Second AHU for central secondary recirculation Series fan-powered One AHU for central primary recirculation Terminal unit fans for local secondary recirculation 36

39 ASHE Std : Ventilation Rate Procedure Dual-Fan, Dual-Duct Both central recirculation paths contain some excess OA cooling air handler heating air handler OA EA DA DA DA zone 1 zone 2 zone 3 Series Fan-Powered Central and local recirculation paths contain some excess OA air handler OA EA SFP DA DA DA zone 1 zone 2 zone 3 37

40 ASHE Std : Ventilation Rate Procedure ASHE Std Appendix A Appendix A gives credit for excess OA in secondary ventilation paths From the heating air handler in a dual-fan, dual-duct system From the ceiling plenum in a series, fan-powered system calculated Ev example Series Fan-Powered air handler OA EA SFP DA zone 1 Vdz = 2600 Voz = 300 DA zone 2 Vdz = 3400 Voz = 400 DA zone 3 Vdz = 4000 Voz =

41 ASHE Std : Ventilation Rate Procedure calculated Ev method* Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) *Two ventilation-air paths calculated Ev example Series Fan-Powered Discharge airflow (Vdz) is constant Zd = Voz / Vdz air handler OA EA SFP DA zone 1 Vdz = 2600 Vpzm= 650 Voz = 300 DA zone 2 Vdz = 3400 Vpzm= 850 Voz = 400 DA zone 3 Vdz = 4000 Vpzm= 1000 Voz = 500 Zd = 0.12 Zd = 0.12 Zd =

42 ASHE Std : Ventilation Rate Procedure calculated Ev method* Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) *Two ventilation-air paths calculated Ev example Uncorrected OA Intake zone Rp Pz Ra Az = = = = = = 150 (Rp Pz) = 610 (Ra Az) = 590 Vou = D (Rp Pz) + (Ra Az) = = 990 cfm 40

43 ASHE Std : Ventilation Rate Procedure calculated Ev method* Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) *Two ventilation-air paths calculated Ev method* Multiple Recirculation Paths 6a. Average OA fraction (Xs) Xs = Vou / Vps 6b. Zone ventilation efficiency (Evz) Evz = (Fa + Xs Fb Zd Fc) / Fa 6c. System ventilation efficiency (Ev) Ev = smallest Evz *Two ventilation-air paths 41

44 ASHE Std : Ventilation Rate Procedure calculated Ev example Series Fan-Powered Vps = LDF Vpz = ,000 = 5,000 cfm air handler OA EA SFP Vpz = 10,000 cfm DA zone 1 Vdz = 2600 Vpz = 2600 DA zone 2 Vdz = 3400 Vpz = 3400 DA zone 3 Vdz = 4000 Vpz = 4000 calculated Ev example* Series Fan-Powered 6a. Calculate average OA fraction (Xs) for the system: Xs = Vou / Vps = 990 / 5000 = 0.20 *Two ventilation-air paths 42

45 ASHE Std : Ventilation Rate Procedure calculated Ev example* Series Fan-Powered 6b. For each zone, determine zone ventilation efficiency (Evz): Evz = (Fa + Xs Fb Zd Fc) / Fa zone Fa Xs Fb Zd Fc Evz *Two ventilation-air paths calculated Ev example* Series Fan-Powered Fraction of discharge air from sources outside the zone (Fa): Fa = Ep + (1 Ep) Er where, Ep = fraction of discharge air (Vdz) that is comprised of primary air (Vpz) Er = fraction of locally recirculated air that is comprised of average recirculated air rather than recirculated directly from the zone *Two ventilation-air paths 43

46 ASHE Std : Ventilation Rate Procedure calculated Ev example Series Fan-Powered Ep = Vpzm / Vdz air handler OA EA SFP DA zone 1 Vdz = 2600 Vpzm= 650 Ep = 0.25 DA zone 2 Vdz = 3400 Vpzm= 850 Ep = 0.25 DA zone 3 Vdz = 4000 Vpzm= 1000 Ep = 0.25 Dual-Fan, Dual-Duct All return air is routed back through central air handlers cooling air handler heating air handler OA EA DA DA DA zone 1 zone 2 zone 3 Er = 1.0 Er = 1.0 Er =

47 ASHE Std : Ventilation Rate Procedure Series Fan-Powered Each terminal-unit fan recirculates some local return air directly back into the zone air handler OA EA SFP DA zone 1 Er = 0 DA zone 2 Er = 0 DA zone 3 Er = 0 Series Fan-Powered Locally-recirculated air is a mixture of air from many zones air handler OA EA SFP DA zone 1 Er = 0.3 DA zone 2 Er = 0.5 DA zone 3 Er =

48 ASHE Std : Ventilation Rate Procedure calculated Ev example* Series Fan-Powered Fraction of discharge air from sources outside the zone (Fa): Fa = Ep + (1 Ep) Er zone Ep Er Fa *Two ventilation-air paths calculated Ev example* Series Fan-Powered Fraction of discharge air from fully mixed primary air (Fb): Fb = Ep zone Ep Fb *Two ventilation-air paths 46

49 ASHE Std : Ventilation Rate Procedure calculated Ev example* Series Fan-Powered Fraction of outdoor air from sources outside the zone (Fc): Fc = 1 (1 Ez) (1 Er) (1 Ep) where Ez = zone air distribution effectiveness zone Ez Er Ep Fc *Two ventilation-air paths calculated Ev example* Series Fan-Powered 6b. For each zone, determine zone ventilation efficiency (Evz): Evz = (Fa+ Xs Fb Zd Fc) / Fa zone Fa Xs Fb Zd Fc Evz *Two ventilation-air paths 47

50 ASHE Std : Ventilation Rate Procedure calculated Ev example Series Fan-Powered 6c. Find system ventilation efficiency (Ev): Ev = smallest Evz = 0.85 zone Fa Xs Fb Zd Fc Evz *Two ventilation-air paths calculated Ev method* Multiple-Zone Recirculating 1. Breathing-zone outdoor airflow (Vbz) 2. Zone air distribution effectiveness (Ez) 3. Zone outdoor airflow (Voz) 4. Zone outdoor air fraction (Zd) 5. Uncorrected outdoor air intake (Vou) 6. System ventilation efficiency (Ev) 7. System outdoor air intake (Vot) *Two ventilation-air paths 48

51 ASHE Std : Ventilation Rate Procedure calculated Ev example Series Fan-Powered Vot = Vou / Ev = 990 / 0.85 = 1160 cfm air handler Vot = 1160 cfm OA EA SFP DA DA DA zone 1 zone 2 zone 3 Voz = 300 Voz = 400 Voz = vs. previous versions Series Fan-Powered Std version Ev method Ev Vot n/a n/a n/a Table Appendix A (dual-path equations) Comparison uses equivalent zone outdoor airflows (Voz), based on ASHE Std Appendix A results in lower Vot than Table

52 ASHE Std : Ventilation Rate Procedure vs. previous versions Series Fan-Powered Std version Ev method Ev Vot n/a n/a n/a Table Appendix A (dual-path equations) Appendix A (single-path equations) Comparison uses equivalent zone outdoor airflows (Voz), based on ASHE Std Dynamic Reset ASHE Standard ventilation requirements 50

53 ASHE Std : Ventilation Rate Procedure section Dynamic Reset System may be designed to reset OA intake flow (Vot) and/or zone airflow in response to: Variations in zone population ( DCV ) Variations in ventilation efficiency due to changes in airflow ( ventilation reset ) Variations in intake airflow ( economizer reset ) dynamic reset Variations in Pz (DCV) Time-of-day schedule Part of building automation system Occupancy sensors Determine occupied vs. unoccupied CO2 sensors Estimate cfm/person ventilation rate 51

54 ASHE Std : Ventilation Rate Procedure dynamic reset Variations in Efficiency As Vps drops, Xs (=Vou/Vps) increases Zp is probably lower than worst case So, Ev (= 1 + Xs Zp) increases Vps = 5500 cfm air handler OA EA zone 1 Vpz = 2000 Voz = 300 Zp = 0.15 zone 2 Vpz = 1500 Voz = 400 Zp = 0.27 zone 3 Vpz = 2000 Voz = 500 Zp = 0.25 dynamic reset Variations in Efficiency central station air handler with controls OA SA Reset outdoor airflow (Vot) communicating BAS Totals (Vou, Vps) Used OA fraction (Xs) Sys vent efficiency (Ev) New OA setpoint (Vot) DDC/ terminals Req d ventilation (Voz) Actual primary flow (Vp) Current ventilation fraction (Zp = Voz/Vpz) 52

55 ASHE Std : Ventilation Rate Procedure ASHE Std : Ventilation Requirements Answers to your questions This concludes the American Institute of Architects Continuing Education System Program ventilation requirements Summary Must use new prescribed rates Must account for system ventilation efficiency May use default Ev it s easier May use calculated Ev it s more accurate May design based on short-term conditions (e.g., average population) May operate based on current conditions (e.g., DCV or ventilation reset) 53

56 ASHE Std : Ventilation Rate Procedure calculation details ASHE Journal Articles See Articles at Oct 2004 Single-zone and dedicated-oa systems Nov 2004 Ventilation for changeover bypass systems Jan 2005 Single-path, multiple-zone systems May 2005 Dual-path, multiple-zone systems references for this broadcast Where to Learn More ASHE ASHE Standard ASHE Standard User s Manual U.S. Green Building Council 54

57 Trane Engineers Newsletter Live series Bibliography ASHE Standard : Ventilation Rate Procedure ASHE Standard American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHE). ANSI/ASHE Standard : Ventilation for Acceptable Indoor Air Quality. Available at Articles Taylor, S. LEED and Standard ASHE Journal 47 (September 2005): S4 S7. Available at Stanke, D. Addendum 62n: Single-zone and dedicated-oa systems. ASHE Journal 46 (October 2004): Available at Stanke, D. Standard Addendum 62n: Ventilation for changeover-bypass systems. ASHE Journal 46 (November 2004): Available at Stanke, D. Addendum 62n: Single-path multiple-zone system design. ASHE Journal 47 (January 2005): Available at Stanke, D. Standard : Designing dual-path, multiple-zone systems. ASHE Journal 47 (May 2005): Available at Trane Publications Stanke, D., and B. Bradley. ASHE 62n Breathes New Life into ASHE Standard 62. Engineers Newsletter 33-1 (2004). Available from: < vol33_1/ ADM_APN010_EN_ pdf> Page 1 of 1