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MECH 8250 Ventilation

MECH 8250 Ventilation. Lecture : February 2 nd. Winter 2014. Topics Covered by this C ourse. Building Ventilation Systems BCBC 2012 ASHRAE 62.1. Natural Ventilation. Mechanical Ventilation. Mechanical Ventilation. Dedicated Outdoor Air Systems (DOAS). Ventilation Standards. BCBC 2012

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MECH 8250 Ventilation

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  1. MECH 8250Ventilation Lecture: February 2nd Winter 2014

  2. Topics Covered by this Course • Building Ventilation Systems • BCBC 2012 • ASHRAE 62.1

  3. Natural Ventilation

  4. Mechanical Ventilation

  5. Mechanical Ventilation Dedicated Outdoor Air Systems (DOAS)

  6. Ventilation Standards BCBC 2012 3.3.5.7: Ventilation of Vestibules 6.2.2.3: For Storage Garage 9.32: Ventilation for Single Dwelling Unit ASHRAE Standard 62 • 62.1: Non-Residential • 62.2: Residential (BCBC 2012 takes over) LEED (Leadership in Environment & Energy Design) - 2004

  7. VENTILATION – BCBC 2012 BCBC 3.3.5.7: Natural Ventilation: Unobstructed area of 0.1m2 for each door that opens into the vestibule BUT not less than 0.4m2 Mechanical Ventilation: 14m3/hr.m2 (0.82 cfm/ft2) for vestibule area

  8. BCBC 3.3.5.7 – Ventilation of Vestibules Natural Ventilation: Unobstructed area of 0.1m2 for each door that opens into the vestibule BUT not less than 0.4m2 Mechanical Ventilation: Supply 14m3/hr.m2 (0.82 cfm/ft2) for vestibule area

  9. BCBC 6.2.2.3 – For Storage Garage Mechanical Ventilation: • Continuous supply of ventilation air @ 14m3/hr.m2 (0.76 cfm/ft2) of the floor area. • When CO and NO2 is detected at higher levels, this ventilation air is increased. 6ACH.

  10. VENTILATION – BCBC 2012 BCBC 9.32.2: Ventilation during Non-Heating Season 9.32.2.2: Natural Ventilation Table 9.32.3.3 Open areas for various rooms 9.32.2.1: Mechanical Ventilation 0.5 ACH for air-conditioning spaces 1.0 ACH for NON air-conditioning spaces

  11. VENTILATION – BCBC 2012 BCBC 9.32.3: Ventilation during Heating Season 9.32.3.3: Principal Ventilation Exhaust Fan OR Dedicated Central Ventilation System

  12. VENTILATION – BCBC 2012 Changes implemented on December 19 2014: • The End of Exhaust-Only Ventilation Systems. Exhaust-only ventilation systems are being replaced by a system that includes both exhaust and supply. • Principal Ventilation System Requirements : Continuous Operation (24 hours a day) • The same Principal Exhaust Fan can be used for Washroom or Kitchen, but when the room is being used, the exhaust will increase to satisfy the exhaust requirements

  13. VENTILATION – BCBC 2012 Ventilation during Heating Season 9.32.3.3: Dedicated Central ventilation System with minimum Ventilation rate

  14. Principal Ventilation System Exhaust Fan A SFD unit shall include: A principal ventilation system including supply (1) and continuous exhaust (2). The bathroom fan (2) provides continuous exhaust as the principal ventilation exhaust fan and intermittent, on command exhaust at a higher air flow rate as a bathroom fan. The kitchen exhaust is provided by a dedicated kitchen exhaust fan (3). The heated crawl space is provided with a dedicated fan (4) and at least one passive grille to the rest of the house (5).

  15. Ducted forced-air furnace The furnace ducting provides supply air to required areas of the dwelling unit and the bathroom fan is designated as the principal ventilation exhaust fan, operating continuously as the principal ventilation exhaust fan (see 9.32.3.5.) and intermittently as a bathroom fan (see 9.32.3.6.).

  16. Use of HRV in Ducted Furnace 9.32.3.4.(3) Using a ducted forced-air furnace in the principal ventilation system. The HRV may act as the principal ventilation exhaust fan and may exhaust from more than one location in the dwelling unit. In this case, the bathroom and kitchen fans are not part of the principal ventilation system.

  17. Topics Covered by this Course • General requirements • LEED Points • Ventilation requirements • Construction and O/M requirements • Energy Efficiency Options • Possible Coming Changes • Questions

  18. ASHRAE – LEED Points • EQ Prerequisite 1: Minimum IAQ • EQ Prerequisite 2: Environmental Tobacco Smoke (ETS) Control • EQ Credit 1: Outdoor Air Delivery Monitoring for CO2 • EQ Credit 2: Increased Ventilation – at least 30% more than ASHRAE 62.1 2004 • EQ Credit 3.1: Construction IAQ Management during Construction • EQ Credit: Construction IAQ Plan before occupancy

  19. 1. Purpose 1.1 The purpose of this standard specify minimum ventilation ratesand other measures intended to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects. 1.2 This standard is intended for regulatory application to newbuildings, additions to existing buildings, and those changes to existing buildings that are identified in the body of the standard. 1.3 This standard is intended to be used to guidethe improvement of indoor air quality in existing buildings.

  20. 2. Scope 2.1 All spaces intended for human occupancy excluding low-rise residential (62.2) 2.2 Defines requirements for ventilation, air-cleaning design, commissioning, installation and O&M 2.3 Additional requirements and other standards may apply (labs, healthcare, industrial, etc.) 2.4 May be applied to both new and existing buildings, not intended to be used retroactively 2.5 Does not prescribe specific ventilation rates for smoking spaces 2.6 Ventilation requirements based on chemical, physical, & biological contaminants 2.7 Consideration or control of thermal comfort is not included 2.8 In addition to ventilation, the standard contains requirements related to certain sources

  21. 2. Scope 2.9 Acceptable IAQ may not be achieved in all buildings meeting these requirements because of: • Diversity of sources and contaminants • Air temperature, humidity, noise, lighting, and psychological/social factors • Varied susceptibility in the occupants • Introduction of outdoor contaminants

  22. 2. DEFINITIONS Acceptable indoor air quality: Air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction. Occupiablespace: an enclosed space intended for human activities, excluding those spaces intended primarily for other purposes, such as storage rooms and equipment rooms, that are only occupied occasionally and for short periods of time.

  23. Ventilation System

  24. 6. PROCEDURES 6.1 General. • Ventilation Rate Procedure or IAQ Procedure for outdoor airflow values for mechanical ventilation systems 6.1.1 Ventilation Rate Procedure. • Prescribes rates & procedures based on typical space contaminant sources & source strengths 6.1.2 IAQ Procedure. • Requires calculation of rates based on analysis of contaminant sources, concentration targets and perceived air quality targets.

  25. 6. PROCEDURES Ventilation Rate Procedure • Most commonly used method • Lookup table (simple) or Appendix A (complex) • Need zone air distribution effectiveness • LEED requires this method Indoor Air Quality Procedure • Design to maintain specific contaminant levels • Mass Balance Analysis • Methods used in similar buildings • Validation by contaminant monitoring

  26. VENTILATION RATE PROCEDURE

  27. VENTILATION RATE PROCEDURE

  28. Ventilation Air (OA) Calculation Step 1 Vbz= RpPz + RaAz • Vbz= Breathing Zone OA • Rp= Outdoor Air Rate per person • Pz= Zone Population • Ra= Outdoor Air Rate per unit area • Az= Zone Floor Area (Net occupiable)

  29. Ventilation Air (OA) Calculation Step 2 Voz=Vbz/Ez • Voz = Ventilation Outdoor Airflow in the zone • Vbz= Breathing Zone Outdoor Airflow • Ez= Effectiveness of the air distribution

  30. COOLING

  31. Induced Ventilation

  32. HEATING

  33. Ventilation Air (OA) Calculation Step 2 Voz=Vbz/Ez • Voz = Ventilation Outdoor Airflow in the zone • Vbz= Breathing Zone Outdoor Airflow • Ez= Effectiveness of the air distribution

  34. Multiple Spaces Vot = Vou/Ev • Vot - Design OA intake flow • Vou - Uncorrected OA intake • Ev - ventilation efficiency from Table 6-3 or Appendix A

  35. General Requirements 4. OUTDOOR AIR QUALITY 5. SYSTEMS AND EQUIPMENT

  36. 4. Outdoor Air Quality 4.1 Regional Air Quality • Must determine NAAQS attainment status • Air cleaning is required in some cases in non-attainment areas 4.2 Local Air Quality • Conduct observational site survey to identify local sources of air contaminants 4.3 Documentation • Regional air quality compliance status • Local survey information • Conclusions regarding acceptability of outdoor air quality

  37. 5. SYSTEMS AND EQUIPMENT 5.1 Natural Ventilation • Location and size of openings • Naturally ventilated spaces shall be permanently open to and within 8 m (25 ft) of operable wall or roof openings to the outdoors, the openablearea of which is a minimum of 4% of the net occupiable floor area. • Louvers based on the free unobstructed area. • Where interior spaces without direct openings to the outdoors are ventilated through adjoining rooms, the opening between rooms shall be permanently unobstructed and have a free area of not less than 8% of the area of the interior room nor less than 25 ft2 (2.3 m2).

  38. VENTILATION – ASHRAE 62.1 5.1 Natural Ventilation Determine the maximum W to qualify for natural ventilation. Minimum size of each operable window. What needs to be changed for the 10’x10’ room to allow natural ventilation? What if the operable windows are changed with a louver with 0.5 free area.

  39. VENTILATION – ASHRAE 62.1 5.1 Natural Ventilation Determine the maximum W to qualify for natural ventilation.Within 25’ of the opening. Therefore the W will be 10’ + 25’ = 35’ Minimum size of each operable window.Opening Size: 4% minimum of the floor areaFloor area: 35’ x 40’ = 1,400 ft2Opening Area = 56ft2Window area: 18.7ft2 (three) What needs to be changed for the 10’x10’ room to allow natural ventilation?The door (>8.5ft high and 3ft wide) must be removed to make the opening permanently unobstructed so that the interior office can have natural ventilation.Greater of the two:8% of floor area = 112 ft2 OR 25ft2 What if the operable windows are changed with a louver with 0.5 free area.56ft2 x 0.5 = 112ft2

  40. 5. SYSTEMS AND EQUIPMENT 5.2 Ventilation Air Distribution • Must provide means to adjust the system (Balancing Dampers) • Minimum ventilation air must be provided to each terminal unit in ceiling/floor plenum systems • Documentation (Air Balancing Reports)

  41. 5. SYSTEMS AND EQUIPMENT 5.3 Exhaust Duct Location • Operate exhaust ducts with harmful contaminants at negative pressure (Install Exhaust Fans at the end of the exhaust duct system) 5.4 Ventilation System Controls • Control to assure proper ventilation under any operating condition 5.5 Airstream Surfaces • Use materials that have documented resistance to microbial growth and erosion

  42. 5. SYSTEMS AND EQUIPMENT 5.6 Outdoor Air Intakes • Location: Separate OA intake from outdoor contaminant sources Must comply with default minimum separation distances in Table 5-1. Examples: • Loading dock 25 ft • Dumpster 15 ft • Surface below intake 1 ft • Cooling tower exhaust 25 ft • Rain Entrainment: Must limit moisture penetration (using hood, proper velocity, etc.) or manage water that penetrates • Rain Intrusion: Prevent moisture intrusion into equipment mounted outdoors • mounted outdoors • Snow Entrainment: Designed to manage melted snow drawn in the system. • Bird Screens: Must use bird screens and prevent bird nesting

  43. 5. SYSTEMS AND EQUIPMENT 5.7 Local Capture of Contaminants • Discharge air from non-combustion equipment that captures contaminants shall be exhausted to the outdoors 5.8 Combustion Air • Follow manufacturer’s instructions to provide sufficient combustion air and exhaust air for indoor fuel-fired appliances • Products of combustion from vented appliances shall be vented directly outdoors

  44. 5. SYSTEMS AND EQUIPMENT 5.9 Particulate Matter Removal • MERV 6 (or gUsea filter rated at MERV 6 (orgreater) upstream of cooling coils and other wet-surface devices in supply stream 5.10 Dehumidification Systems • Must be able to limit indoor RH to 65%or less at design dew point condition • Exception to RH limit - where occupancy requirements or processes dictate higher RH conditions • Intake airflow must be greater than relief/exhaust during cooling (to minimize moist air infiltration)

  45. 5. SYSTEMS AND EQUIPMENT At 75F, 65% RH, safety Margin is 13F before condensation occures. 62F DP

  46. 5. SYSTEMS AND EQUIPMENT 5.11 Drain Pans • Assure drainage without flooding or carryover • Slope: 0.125” (1/8”) per foot toward outlet • Drain: located at lowest point, with sufficient diameter prevent overflow • Drain seal: Shall include P-trap or other seal for negatively pressurized drain pans to prevent ingestion of air while allowing complete drainage (fan on or off) • Pan size: length at least 1/2 coil height or as necessary to limit carryover

  47. 5. SYSTEMS AND EQUIPMENT 5.12 Finned Tube Coils and Heat Exchangers • Use drain pan • Select to limit coil pressure drop to 0.75 in.wc.@ 500 fpm face velocity • If higher pressure drop, provide access on both sides for maintenance 5.13 Humidifiers and Water Spray Systems • Use potable water (or better) • No downstream devices within absorption distance 5.14 Access for Inspection, Cleaning and Maintenance.

  48. 5. SYSTEMS AND EQUIPMENT 5.15 Building Envelope and Interior Surfaces • Weather barrier to prevent water penetration into envelope • Vapor retarder or other means to prevent condensation on cold surfaces within envelope • Seal all seams, joints, penetrations to limit infiltration • Insulate pipes, ducts expected to have surface temperature below surrounding dew point 5.16 Buildings with Attached Parking Garages. Limit infiltration of vehicular exhaust • Maintain garage pressure at or below adjacent occupied space • Or, use a vestibule • Or, otherwise design to minimize air migration from garage to occupied space

  49. 5. SYSTEMS AND EQUIPMENT 5.17 Air Classification and Recirculation • Limit recirculation or transfer of “dirty” air to “cleaner” spaces 5.17.1 Classification • Designate air leaving each space using Table 6.1 • Class 1: Low contaminant concentration (office) • Class 2: Moderate concentration (dining room) • Class 3: Significant concentration (sick room) • Class 4: Highly objectionable or potentially harmful concentration

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