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 FansCODE for Baths with bathing or spas facilities: Minimum 80 CFM Intermittent Ventilation

required or

Continuous 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