MECH 8250 Ventilation Winter 2014 Lecture: February 2 nd 08/09/2014 - - PDF document
2/3/2015 MECH 8250 Ventilation Winter 2014 Lecture: February 2 nd 08/09/2014 1 Topics Covered by this Course Building Ventilation Systems BCBC 2012 ASHRAE 62.1 03/02/2015 2 1 2/3/2015 Natural Ventilation 03/02/2015 3 Mechanical
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Dedicated Outdoor Air Systems (DOAS)
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– 62.1: Non‐Residential – 62.2: Residential (BCBC 2012 takes over)
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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
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Changes implemented on December 19 2014: 1. The End of Exhaust‐Only Ventilation Systems. Exhaust‐only ventilation systems are being replaced by a system that includes both exhaust and supply. 2. Principal Ventilation System Requirements : Continuous Operation (24 hours a day) 3. 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
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Ventilation during Heating Season 9.32.3.3: Dedicated Central ventilation System with minimum Ventilation rate
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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).
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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.).
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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.
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62.1 2004
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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
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– Diversity of sources and contaminants – Air temperature, humidity, noise, lighting, and psychological/social factors – Varied susceptibility in the occupants – Introduction of outdoor contaminants
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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. Occupiable space: 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.
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COOLING
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Induced Ventilation
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HEATING
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areas
air contaminants
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and within 8 m (25 ft) of operable wall or roof openings to the outdoors, the openable area of which is a minimum of 4% of the net occupiable floor area.
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).
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qualify for natural ventilation.
window.
the 10’x10’ room to allow natural ventilation?
are changed with a louver with 0.5 free area.
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Within 25’ of the opening. Therefore the W will be 10’ + 25’ = 35’
Opening Size: 4% minimum of the floor area Floor area: 35’ x 40’ = 1,400 ft2 Opening Area = 56ft2 Window area: 18.7ft2 (three)
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
56ft2 x 0.5 = 112ft2
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negative pressure (Install Exhaust Fans at the end of the exhaust duct system)
condition
growth and erosion
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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:
25 ft
15 ft
1 ft
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
– mounted outdoors – Snow Entrainment: Designed to manage melted snow drawn in the system. – Bird Screens: Must use bird screens and prevent bird nesting
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the outdoors
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– 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)
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62F DP At 75F, 65% RH, safety Margin is 13F before condensation occures.
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– 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
– Maintain garage pressure at or below adjacent occupied space – Or, use a vestibule – Or, otherwise design to minimize air migration from garage to
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5.17.2 Re‐Designation: 1. Air Cleaning. May reclassify air cleaned by passing it through an appropriate air‐cleaning system 2. Energy Recovery. Energy recovery ok:
1. class 2 (exhaust) airstreams must have no more than 10% leakage into a class 1 airstream. 2. class 3 (exhaust) airstreams must have no more than 5% leakage into a class 1 airstream.
3.
5.17.2 Recirculation Limitations: Manage recirculation as follows
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7.1 Construction Phase
– Don’t operate air handlers without filters – Protect building materials – Protect occupied areas – Limit migration of construction contamination into occupied space – Air Duct Construction shall be in accordance with the SMACNA duct construction standards and NFPA standards governing installation of HVAC systems
7.2 System Start‐up
– Balance airflow values, test drain pans, clean up before starting, test damper controls – Documentation including balance report, construction drawings and design criteria with assumptions shall be provided to Owner
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6 2 -2 0 0 1
6 2 -1 9 9 9
ventilation m etric 6 2 - 1 9 8 9
Therm al Com fort
Proc.
6 2 - 1 9 7 3 first issued 6 2 - 1 9 8 1 Alternative Air Quality Proc. 1 9 9 0 2 0 0 0 2 0 1 0 1 9 7 0 1 9 8 0 6 2 .1 -2 0 0 4
6 2 .1 -2 0 0 7 Updated
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