Local Exhaust Fans
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Local Exhaust Fans
Local Exhaust Fans
Biological ContaminatesMoistureCombustion gases - If not burned properly can intro. CO.
Gas cooktopsGas ovensFurnaceGas Hot H20 heatersWoodstovesLeaky chimneys
Multi Point Ventilation
Heat Recovery Ventilator
HRV
HRV
Bath Ventilation
Bathroom Exhaust Fans
Bathroom Exhaust Fans
CODE for Baths with bathing or spas facilities:
Minimum 80 CFM Intermittent Ventilation required
orContinuous Ventilation System at 20 cfm
CODE for Toilet Rooms without bathing or spas facilities:
3SF Minimum Window ½ of which must be openable Minimum 50 CFM Intermittent Ventilation
Home Ventilation Institute Recommendations - Baths
Bathrooms to 80SF - 80CFM fan (Code) Bathrooms 81sf to 100 sf – 1 cfm per
square foot (~ 8 air changes/hour) Bathrooms over 100 sf add the CFM for
each fixture Allow 50 CFM per standard toilets, shower
and steam shower (put on timer) Allow 100 CFM per Whirlpool, garden and hot
tubs
HVI recommends continuous ventilations as augmentation to intermitent venilation
Bathroom Exhaust Fans
A toilet in its own enclosure should have its own fan
Fans approved for wet areas should be placed over or very near the shower or tub when possible.
Bath doors should be undercut at least 3/4”
Leave fan on for 20 minutes after use of the bathroom
Web Resource
HVACquick.com Home Ventilation Institute
Ventilation Considerations
Fan Type Propeller Fan – Limited air capacity and noisy
Axial Fan – Better air movement but still noisy
Centrifugal Blower (Squirrel Cage) The best
Propeller Fan
Axial Fan
Centrifugal Blower
Sound Levels
Sound is measured in Sones
1-Sone equals the loudness of a pure tone having a frequency of 1,000 hertz at 40 decibels.
Decibels
0 -The softest sound a person can hear with normal hearing
10 -Normal breathing 20 Whispering at 5 feet 30 Soft whisper 50 Rainfall 60 Normal conversation 110 Shouting in ear 120 Thunder .9 Sones = approx. 28.2 decibels
Sones
The Home Ventilation Institute sets a limit of 9.0 sones for kitchen fans up to 500 CFM
Reference – A fan with a sone rating of 8.0 sones is twice as loud as one rated at 4.0 sones.
Reference - Refrigerators run at about 1.0 sone.
In-Line Ventilator Fan 110 CFM 1.0 Sones 210 CFM 2.0 Sones
Broan Silent Series 110 cfm .7 Sones
Switching Fans
Humidistat
Kitchen Ventilation
Kitchen Exhaust Fans
CODE (ASHRAE) The American Society of Heating, Refrigerating and Air-Conditioning Engineers
100 CFM IntermittentOr25 CFM Continuous
Home Ventilation Institute Recommendations - Kitchens
Wall Mount Hoods – 100 cfm per foot of width
Island Mount Hoods – 150 cfm per foot of width
Air Flow Rules of Thumb
Rule of Thumb 1:Take the hood area (in square feet) and multiply it by 75 to get the CFM (cubic feet per minute) for a wall hood, or multiply it by 100 for an island hood.
Rule of Thumb 2:Allow 15 air changes per hour (ACH) for the kitchen. Take the kitchen volume (length x width x height) and divide by 4 to get the required CFM.
Air Flow Rules of Thumb
Rule of Thumb 3:Allow 1 CFM per 100 BTU's per hour (BTUH) heat output.Take the output of the oven and cooktop (if together or close) and divide by 100 to get the required CFM.
Rule of Thumb 4: (this applies to commercial type ranges)Allow 100 CFM per linear foot of hood.Take the perimeter of the hood and multiply it by 100 to get the required CFM.
Which rule of thumb is the best one to use?The most popular rules of thumb are #1 and #3. We typically use rule of thumb #1 when we size fans.
NKBA Recommendations
Multi Point Ventilation
Vented Hood System
Recirculating Fan in Microwave Combo
Kitchen Ventilation (HOGSS)
Heat Odor Grease Steam Smoke
Recirculating Range Hood
Recirculating Ventilation System
This type of system will only remove two Heat Steam
Downdraft
Down Draft Ventilation
Down Draft Ventilation
Range Hood Installation
Integral Fan Vented Through Roof
In Line Fan
Integral Through Soffit
Remote Ventilator
Through Crawlspace
Down Draft Through Floor
Down Draft Through Roof
Kitchen Ventilation Considerations
Fan – 300 CFM minimum Ducted Duct run lengths
Interior Fan (power) Keep duct runs as short and
straight as possible. 6” round or 3 ¼” x 10 rectangular
ducts Maximum run = 25’ maximum
Kitchen Ventilation Considerations
Exterior or In-Line Fan (power) 9” round or 3 ¼” x 14”
rectangular duct Maximum run = 55’ maximum
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