ASHRAE Std Update Where Are We Now?

Transcription

1 ASHRAE Std Update Where Are We Now? October 2012 Dennis A. Stanke Trane La Crosse, WI

2 ASHRAE Standard 62.1 What Is It? Title: Ventilation for Acceptable Indoor Air Quality Purpose: to specify minimum ventilation rates and indoor air quality that will be acceptable to human occupants and are intended to minimize adverse health effects. Scope: All commercial, institutional, and high-rise residential buildings 2

3 ASHRAE Standard 62.1 Why Care? Section 6 is the basis for many ventilation codes, include both US model codes (UMC and IMC) Compliance with Std (Sections 4 thru 7) is a LEED prerequisite for any credits Compliance with Std (Sections 4 thru 8) is required for compliance with: Std High Performance Green Buildings ENERGY STAR and beq energy label 4

4 what does Std 62.1 require? Must Comply With (Sect 4 and 5) Mandatory general requirements To reduce generation of indoor contaminants and introduction of outdoor contaminants (Sect 6) Ventilation requirements Prescribed rates to dilute indoor contaminants Performance rates to limit contaminant concentrations Natural ventilation provisions (Sect 7) Mandatory construction, startup reqmts (Sect 8) Mandatory operation, maintenance reqmts 5

5 Std Section 4 Outdoor Air Quality Project Team Regional Air Quality. Assess regional outdoor air (OA) quality to determine NAAQS compliance status Check for non-attainment for any EPA criteria contaminants Local Air Quality. Survey site for unusual local sources Visit the site, look around These assessments inform air cleaning decisions 6

6 Std Section 5 Systems and Equipment Mech Designer 5.1 Ventilation Air Distribution. Design to assure that ventilation air can get to occupied zones Provide means to adjust (balance) airflows Design to assure mixing in RA/OA mixing plenums Document assumptions and air balancing requirements Important in 100% OA systems should really duct OA to zone 7

7 Std Section 5 Systems and Equipment Mech Designer 5.2 Exhaust Duct Location. Prevent leakage of harmful exhaust contaminants into the building Design exhaust ducts to operate at negative pressure Room Duct Fan Outdoors 8

8 Std Section 5 Systems and Equipment Mech Designer 5.3 Ventilation System Controls. Design to assure minimum ventilation Provide controls to enable fan Provide controls to maintain minimum OA flow at any load or dynamic reset condition. VAV systems must include modulating dampers or injection fans 9

9 Std Section 5 Systems and Equipment Mech Designer 5.4 Airstream Surfaces. Reduce space contamination due to air distribution system Use duct materials that resist microbial growth per UL 181 Use duct materials that resist erosion per UL 181 Most matte-face finishes meet these requirements 10

10 Std Section 5 Systems and Equipment architect 5.5 Outdoor Air Intakes. Reduce contamination from outdoors Locate intake a minimum distance from outdoor sources, per Table 5.2. Examples sources/distances: Loading dock Dumpster Surface below intake Cooling tower exhaust 25 ft 15 ft 1 ft 25 ft Design to limit rain water penetration (using hood, proper velocity, etc.) or manage water that penetrates Use bird screens and prevent bird nesting at intake 11

11 Std Section 5 Systems and Equipment Mech Designer 5.6 Local Capture of Contaminants. Reduce recirculation of indoor contaminants Exhaust locally captured contaminants (from printers, for instance) directly to outdoors 5.7 Combustion Air. Reduce pollutants from combustion appliances Provide sufficient combustion air Provide sufficient air for removal of combustion products 12

12 Std Section 5 Systems and Equipment Mech Designer 5.8 Particulate Matter Removal. Reduce rate of dirt accumulation on HVAC devices Use at least a MERV 6 filter upstream of dehumidifying coils and other wet-surface devices (about 20% to 30% Dust Spot) 13

13 Std Section 5 Systems and Equipment Mech Designer 5.9 Dehumidification Systems. Design to reduce dampness in buildings during mechanical cooling By analysis, limit RH to 65% or less at design dew point condition without solar load Design so that intake exceeds exhaust airflow Basic constant volume systems with sensible-only thermostat might not comply with 65% limit 14

14 Std Section 5 Systems and Equipment Mech Designer 5.10 Drain Pans. Assure condensate drainage without flooding or carryover Slope drain pan at least 1/8 per foot Locate drain opening at lowest point of drain pan and size to prevent overflow under normal conditions Use P-trap or other seal to prevent ingestion of air while allowing complete drainage with fan on or off Size drain pan to limit carryover Proper P-trap design helps avoid common water carryover problems 15

15 Drain Seals Mech Designer total trap height T = D + H where H = air-handler casing pressure + 1 in. wg D = trap depth = ½ H + d d = drain pipe diameter 16

16 Std Section 5 Systems and Equipment Mech Designer 5.11 Finned Tube Coils and Heat Exchangers. Select to reduce water droplet carryover Limit coil pressure drop to 0.75 in.wc.@ 500 fpm Exception: No pressure drop limit when design provides access to both faces for cleaning 5.12 Humidifiers and Water Spray Systems. Reduce water-borne contaminants and design to reduce carryover Use potable water No downstream devices within absorption distance 17

17 Std Section 5 Systems and Equipment Mech Designer 5.13 Access for Inspection, Cleaning and Maintenance. Reduce dirt accumulation in air distribution system Design system with adequate clearance around ventilation equipment Provide access doors/panels for ventilation equipment (air handlers, terminal units) Provide access doors/panels for devices in air distribution system (air plenums, coils, air cleaners, drain pans, fans, humidifiers) 18

18 Std Section 5 Systems and Equipment Architect 5.14 Building Envelope and Interior Surfaces. Reduce intrusion of water and water vapor and uncontrolled condensation Use a weather barrier within the building envelope Use a vapor retarder within the building envelope (typically on the warm side, but it really depends on wall design) Seal all envelope seams, joints and penetrations Insulate pipes, ducts and other cold surfaces 19

19 Std Section 5 Systems and Equipment Architect 5.15 Buildings with Attached Parking Garages. Reduce infiltration of vehicular exhaust Maintain garage pressure below adjacent occupied space Or, use a vestibule Or, otherwise design to minimize air migration from garage to occupied space 20

20 Std Section 5 Systems and Equipment Mech Designer 5.16 Air Classification and Recirculation. Reduce recirculation of dirty air to cleaner spaces Designate air from each space/location (see Table 6.1) Class 1: Low contaminant concentration (office) Class 2: Mild concentration (dining room) Class 3: Significant concentration (daycare sick room) Class 4: Highly objectionable/potentially harmful Design to limit air recirculation as follows: Class 1 to any space or location Class 2 to self, other Class 2 or Class 3 Class 3 to self Class 4 to outdoors only 21

21 Std Section 5 Systems and Equipment Project Team 5.17 Buildings Containing ETS Areas and ETS-Free Areas. Reduce level of ETS in ETS-free areas Classify each area as ETS or ETS-free Pressurize ETS-free areas with respect to ETS areas Separate ETS/ETS-free areas with solid walls, doors, etc (or engineer to assure airflow into ETS areas Maintain transfer airflow paths Don t recirculate from ETS to ETS-free at air handler Exhaust from ETS areas Post sign: This area may contain ETS 22

22 what does Std 62.1 require? Must Comply With (Sect 4 and 5) Mandatory general requirements To reduce generation of indoor contaminants and introduction of outdoor contaminants (Sect 6) Ventilation requirements Prescribed rates to dilute indoor contaminants Performance rates to limit contaminant concentrations Natural ventilation provisions (Sect 7) Mandatory construction, startup reqmts (Sect 8) Mandatory operation, maintenance reqmts 23

23 Std Section 6.0 Procedures Mech Designer 6.1 General. Find minimum zone and intake OA flow using either the VRP, the IAQP, or the NVP Ventilation Rate Procedure (VRP). Prescribes procedures and OA rates, assuming typical space contaminant sources and source strengths IAQ Procedure (IAQP). Requires analysis of contaminants ( performance ) based on sources and target concentrations to find minimum OA rates Natural Ventilation Procedure (NVP). Prescribes opening areas, and requires mechanical ventilation in most climates (mixed-mode ventilation) 24

24 Std Section 6.2 Ventilation Rate Procedure Mech Designer 6.2 Ventilation Rate Procedure. Find OA intake flow (Vot) using prescribed zone OA rates & system intake calculation procedures in this section 25

25 Std Section 6.2 Ventilation Rate Procedure Mech Designer Outdoor Air Treatment. If OA is unacceptable per Section 4.1 assessment, must use air cleaning PM10. Where PM10 exceeds the NAAQS (nonattainment areas), use MERV 6 filter PM2.5. Where PM2.5 exceeds the NAAQS (non-attainment areas) use MERV 11 filter Ozone. Where ozone greatly exceeds the NAAQS (very high non-attainment area) use 40% efficient ozone air cleaner NAAQS: the most recent three-year average annual fourthhighest daily maximum eight-hour average ozone concentration exceeds ppm (209 μg/m3) 26

26 Std Section 6.2 VRP Zone Calculaitons Mech Designer Zone Calculations. To assure reasonable breathing-zone dilution for each zone: Use Table 6.1 rates (cfm/per and cfm/sf) and Equation 6-1 to find breathing zone outdoor airflow: Vbz = Rp*Pz + Ra*Az Use Table 6.2 defaults to find zone air distribution effectiveness, Ez (typically 1.0 for cooling) Use Equation 6-2 to find zone outdoor airflow: Voz = Vbz/Ez 30

27 ventilation rate procedure Minimum Ventilation Rates Mech Designer Table 6-1: Minimum breathing-zone rates for 63 categories Std Std Rp Ra Rp Ra Occupancy category cfm/p cfm/ft² cfm/p cfm/ft² Office Classroom (ages 5-8) Lecture classroom Retail sales Auditorium Prescribes both per-person and per-area rates 31

28 ventilation rate procedure Effective Minimum Rates Mech Designer Comparison of breathing-zone OA flow Std Std Occupancy category (default density/1000 ft²) Vbz cfm Effective cfm/p Vbz cfm Effective cfm/p Office (5p) Classroom (ages 5-8) (25p) Lecture classroom (65p) Retail sales (20p) Auditorium (150p) % of OA rates drop; 30% stay same or rise 32

29 Std Section 6.2 VRP System Calculations Mech Designer Single-Zone Systems. For ventilation systems with one air handler per zone: Find system-level outdoor air intake flow: Vot = Voz % Outdoor Air Systems. For ventilation systems with one air handler supplying only outdoor air to many zones. Find system-level outdoor air intake flow: Vot = S Voz 33

30 Std Section 6.2 VRP System Calculations Mech Designer Multiple-Zone Recirculating Systems. For ventilation systems with one AHU serving many zones: Find outdoor air intake flow (Vot) using prescribed equations and procedure to account for system ventilation efficiency (Ev): Vot = Vou/Ev outdoor air intake flow Vou = D* S Rp*Pz + S Ra*Az OA used in zones D = Ps/ S Pz population diversity factor Ev = min(evz) system vent efficiency Evz = 1 + Xs Zpz zone vent efficiency Xs = Vou/Vps average OA fraction Zpz = Voz/Vpz zone primary OA fraction 34

31 Std Section 6.2 VRP System Calculations Mech Designer For design, Vpz = Vpz-exp, where Vpz-exp is the lowest expected primary airflow at the design condition. I use the Multiple-Zone Recirculating Systems. For reheat minimum airflow setting, Vpzm; it s easy but very ventilation systems with one AHU serving many zones: conservative. Find outdoor air intake flow (Vot) using prescribed equations and procedure to account for system ventilation efficiency (Ev): For design, Vps = Vps-exp, where Vps-exp is the highest expected system primary airflow value at the Vot = Vou/Ev outdoor air intake flow design Vou condition. = D* S Rp*Pz I use + fan S Ra*Az block airflow OA used Vps-des: in zones it s easy and usually D = Ps/ worst-case. S Pz population diversity factor Ev = min(evz) system vent efficiency Evz = 1 + Xs Zpz zone vent efficiency Xs = Vou/Vps average OA fraction Zpz = Voz/Vpz zone primary OA fraction 35

32 Std Section 6.2 OA Calculation Example Do we have time for an example? No But, I found total OA intake for a 6-zone school, using different systems and methods: One RTU per zone (six single-zone systems), both in cooling and heating One FC per zone, and a 100% OA system, with both CV and VAV ventilation airflow A reheat VAV (single-path multiple-zone) system using both default Ev and calculated Ev A series fan-powered VAV (dual-path multiple-zone) system using calculated Ev 36

33 VRP 6-zone school example OA Intake Flow Summary Ventilation System OA Intake (2001 Vot) OA Intake (2010 Vot) % Chg Single-Zone Clg 12,600 8, Single-Zone Htg 15,800 11, % OA CV 12,600 8, % OA VAV 8,800 7, MZS-VAV Default Ev 10,900 10,800-1 MZS-VAV Calc Ev 10,900 8, MZS-VAV Series FP 10,900 7,

34 Std Section 6.2 VRP Dynamic Reset Mech Designer Dynamic Reset. To assure outdoor airflow meets requirement for ventilation load, without over-ventilating, optional controls may: Reset zone minimum OA flow based on variations in occupancy, i.e., demand controlled ventilation (DCV) Reset OA intake flow based on variations in ventilation efficiency (ventilation reset control) Reset VAV zone minimum airflow based on variations in outdoor air fraction due to free cooling or exhaust-air make-up operation This Section includes operating control options, (rather than design requirements) 43

35 Std Section 6.3 IAQ Procedure Mech Designer 6.3. Indoor Air Quality (IAQ) Procedure Find breathing zone OA flow (Vbz) and system OA intake flow (Vot) based on performance Compliance addresses Contaminant sources Contaminant concentration Perceived indoor air quality Design approach Combined IAQP and VRP Documentation 44

36 Std Section 6.3 IAQ Procedure Mech Designer Contaminant Sources. Must identify contaminants of concern including mixtures, sources, source strengths Contaminant Concentration. Must specify target concentration, for each C of C Perceived IAQ. Must specify target perceived air quality in terms of percent satisfied Requires designer judgment to identify contaminants/mixtures of concern, source and source strength for each, targets concentrations. Judgment = Risk 45

37 Std Section 6.3 IAQ Procedure Mech Designer Design Approaches. Find highest required zone and system OA flow rates using: Mass balance analysis AND Subjective evaluation, either after construction, OR using OA needed in a substantially similar zone Combined IAQP and VRP. May use VRP to find minimum OA and IAQP to find additional OA (or air cleaning required) Documentation. Must document assumptions and calculations. IAQP meets Std 62.1 but does NOT meet Std or LEED requirements 46

38 Std Section 6 Natural Ventilation Project Team 6.4 Natural Ventilation Procedure. Use NV with mechanical ventilation in most climates: Perimeter areas must be within defined distance from OA opening with free area at least 4% of floor area Interior areas must be within defined distance from OA opening, and interior-perimeter opening with free area at least 8% of interior floor area, but not less than 25 ft 2 Defined distance depends on window location and ceiling height (2H for single-side, 5H for doubleside) Mixed mode controls must coordinate operation of NV and MV systems 47

39 Std Section 6.5 Exhaust Ventilation Mech Designer Exhaust Ventilation. To assure minimum removal of local contaminants, some zones require exhaust rates prescribed in Table 6.4. Examples of more than 20 zones listed: Art classroom 0.70 cfm/ft2 Beauty and nail salons 0.60 Kitchenettes 0.30 Locker/dressing rooms 0.25 Copy, printing rooms 0.50 Toilet public 50 (cont.) or 70 (cyc.) cfm/wtr closet 48

40 what does Std 62.1 require? Must Comply With (Sect 4 and 5) Mandatory general requirements To reduce generation of indoor contaminants and introduction of outdoor contaminants (Sect 6) Ventilation requirements Prescribed rates to dilute indoor contaminants Performance rates to limit contaminant concentrations (Sect 7) Mandatory construction, startup reqmts (Sect 8) Mandatory operation, maintenance reqmts 49

41 Std Section 7 Construction/Start-Up Project Team 7.1 Construction Phase. Must reduce IAQ problems introduced during construction. For example: Install unit filters before operating fans Protect materials from rain and moisture. Don t install materials with visible microbial growth Reduce transfer of construction contaminants into occupied areas Construct ducts per SMACNA standards 50

42 Std Section 7 Construction/Start-Up Project Team 7.2 System Start-Up. Must reduce potential for IAQ problems prior to occupancy. For example: Balance air flows Test (or certify) drain pan drainage Clean air distribution system before start up Test OA dampers for proper operation Provide ventilation system documentation (HVAC controls information, air balance report, design criteria and assumptions, drawings, etc.) to owner or owner s agent 51

43 Std Section Operation & Maintenance Project Team 8.2 Operations and Maintenance Manual. Develop a building operations and maintenance manual 8.3 Ventilation System Operation. Operate it whenever spaces are expected to be occupied 8.4 Ventilation System Maintenance. Maintain it in accordance with Manual Compliance with Section 8 is required by Std but not by LEED 52

44 Std Summary The 2010 version has a few new requirements It s continually improved (next version in 2013) It s VRP rates and procedures are required by IMC and UMC and by LEED It s required by reference in Std 189.1, which is one of two IgCC project compliance paths We re out of time! 53

45 Questions? ASHRAE 62.1 update: Where are we now?