92474754 Exhaust Fan Guide

7/30/2019 92474754 Exhaust Fan Guide

1/5

A Guide To Ventilation Exhaust Fans

Most of todays new homes are highly insulated and practically air tight. While this is greatas far as cost effective energy bills go, the down side to tightly insulated homes is poor

indoor air quality. As windows and doors are typically kept shut throughout the day,moisture, and stale air that can carry contaminants and pathogens circulates inside homes

and gives rise to various problems including mold and mildew, health problems, ruinedfurniture, peeling paint etc. This is why it is important that you take every step to improve

the quality of your indoor air, which can be achieved through mechanical ventilation.An excellent way to ventilate your home thoroughly, efficiently, and cheaply is to install

exhaust fans in your home. This article explains what exhaust fans are, their different types,how to select the best one for your home, and also the benefits of exhaust ventilation fans.What Are Exhaust FansAn exhaust fan is a mechanical ventilation device that helps to draw out stale and impure

air from your home and bring in fresh air, thereby improving the quality of indoor air.

Exhaust fans are typically ducted to the exteriors of your house, through which bad indoor

air can effectively be removed from your living space.Types Of Exhaust FansExhaust fans are classified into various types, mainly depending on the type of mount and

the location where you need to install the fans. The different types are:1. Ceiling Mounted Exhaust Fans: As the name suggests, ceiling exhaust fans are thosewhich are installed in the ceiling. Such fans expel stale air from your home upwards through

the roof. The fan is connected to ducting, which is exhausted outside the home via anexternal vent, like a roof cap or soffit exhaust vent.2. Inline Exhaust Fans: Unlike ceiling exhaust fans that are installed directly into theceiling, inline exhaust fans are typically mounted in-between ducting, hence the name inlinefan. For instance, if you wanted to ventilate an area that did not have clearance or space fora ceiling mount fan, you would make use of inline exhaust fans to ventilate such areas. The

exhaust fan would be placed in between the ductwork and the stale air would travel throughthe ducts and ultimately be expelled from your home. Since inline fans are not mounteddirectly to the ceiling, they are very quiet. When installing an inline fan, to reduce noise,

we recommend using an insulated flex duct that is at least eight feet long from the intake

port on the ceiling to the inline fan.Inline exhaust fans are ideal for exhausting areas or rooms where you cannot, or do not

wish to install the exhaust fan directly. Since these types of exhaust fans are mounted inremote areas, they are also referred to as remote mounted exhaust fans. Inline exhaust

fans can either be single-port (exhausting from a single area) or multi-port (exhaustingfrom multiple areas).3. Wall Mounted Exhaust Fans: These exhaust fans are installed on walls. Since they are

installed on exterior walls of the home and not on interior walls, the stale air has a direct

route to the outside of your home and thus no duct work is required in installing theseexhaust fans.


2/5

4. Combination Exhaust Fans: Exhaust fans are also available as combination units. You

have the choice of a fan-light combination where the exhaust fan provides illumination as

well, or heat-fan-light combination wherein you get a heater, light and ventilating fan all ina single device.5. Exterior Remote Mounted Exhaust Fans: While most other exhaust fans are installed

inside your home and push stale air out, exterior remote mounted fans are installed outsideyour home and pull out stale indoor air instead of pushing it out. The main benefit of these

exhaust fans is that regardless of however noisy they are, most of the noise remainsoutside your home.6. Kitchen Range Exhaust Fans: These fans are mounted inside the range hood over yourkitchen stove. Such fans not only help to rid your kitchen of stale air but also help to expel

bad odors and reduce moisture levels in your cooking area.These several types of exhaust fans can be used for complete ventilation of your homeincluding intermittent local ventilation for baths, kitchens, dryer rooms; continuous whole

house ventilation throughout your home, and for exhausting hard-to-air spaces such as

crawl spaces, attics, and basements.Benefits Of Exhaust FansExhaust fans are very effective at ventilating your home and other living spaces. Withoutproper ventilation, the air inside your home can get filled with harmful contaminants and

disease causing pathogens.Pollutants such as pesticides, harmful gases, smoke, pet dander, lead, asbestos, dust mites,paint fumes, grease etc get released into indoor air due to daily activities such as cooking,

smoking, burning fuel, bathing, renovating etc. In addition to these pollutants, activitiessuch as bathing, cooking, and washing also release excess moisture in the air and makeindoor air extremely humid. If not ventilated adequately, these added pollutants and

increased moisture levels can decrease the quality of indoor air greatly, thereby leading tovarious problems such as:

Health problems including asthma, allergies, nose bleeds, skin rashes, headaches,nausea, and other breathing disorders. In fact, according to the EnvironmentalProtection Agency, a large percentage of the over 20 million annual asthma cases inthe US alone can be attributed to bad indoor air quality.

Split, warped and rotted furniture due to excess humidity. Cracked and peeling paint on the walls. Formation of fungus, mold spores, and mildew, which in turn lead to severe health

problems.Thus, by using exhaust fans to ventilate your home efficiently and completely, thereby

improving indoor air quality, you can rid yourself and your home of all these problems.Recommended Sizing Of Exhaust FansTo ventilate your home effectively, it is important that the exhaust fan you choose has the

capacity to exhaust the intended space completely. To ensure this, you must select the rightsized fan for your needs. Heres a look at how to size exhaust fans properly.1. Location of the Exhaust Fan and Air Changes Per Hour:


3/5

Where you intend to install the exhaust fan will have a direct bearing on its size. As per the

Home Ventilating Institute (HVI), different locations in your home require varying AirChanges Per Hour (ACH) in order to be ventilated properly. Here are the ACH requirements

recommended by HVI. 8 ACH for bathrooms 15 ACH for kitchens 6 ACH for rooms other than bath and kitchen

ACH refers to the number of times the air should be completely changed in an hour. Thus,

an 8 ACH recommendation for bathrooms means the exhaust fan should have the capacityto completely change the air in the bathroom 8 times in one hour.All exhaust fans are rated in CFM, which refers to Cubic Feet per Minute. To determine howlarge an exhaust fan you need (in other words, CFM rating of the fan) heres what you needto do.Sizing Bathroom Exhaust Fans:First and foremost, measure the dimensions (length, width, and height) of the room and

then calculate the volume of air in the room by multiplying all these 3 numbers. Forinstance, if your bathroom has dimensions of 6 x 10 x 8, then the air volume in thebathroom is 480 cubic feet. Thus, the exhaust fan needs to ventilate 480 cubic feet of air in

order to achieve 1 ACH. But since the recommended ACH for bathrooms is 8, the fan will

effectively need to ventilate 480 x 8 cubic feet, which equals 3840 cubic feet in one hour.Fan ratings are per minute, thus by dividing 3840 by 60, you can achieve the desired CFMrating for the fan which in this case is 64.A simpler way of determining the CFM rating for bathroom exhaust fans is to simply multiplythe length of the bathroom by its width. For every 1 sq. ft. of floor area, you need 1 CFM.

Thus, in the above example, area would be 6 x 10 = 60, thus recommended fan size wouldbe 60 CFM.However, if your bathroom is more than 100 sq. ft. in size, you have to add the different

fixtures in your bathroom to reach the desired CFM rating. The recommended CFM fordifferent fixtures is:

Shower 50 CFM Toilet 50 CFM Bathtub 50 CFM Whirlpool tub 100 CFM

Thus, if your bathroom is more than 100 sq. ft. in size and has a toilet and shower, you will

need an exhaust fan with 100 CFM rating. If a bathtub is also present the CFM rating willincrease to 150 and so on.Sizing Kitchen Exhaust Fans:When sizing an exhaust fan for the kitchen, you have to take into account the location ofyour kitchen cooking range (if without range hood) or the size and location of the rangehood if there is one. Here are the recommended CFM ratings for kitchen range hood exhaust

fans:


4/5

Generally speaking, for every 10,000 BTU of the range, it is recommended a minimum of100 CFM. So if your range is rated at 50,000 btu's, you would consider getting a fan with at

least 500 CFM.2. Understanding Static Pressure and Measuring Equivalent Duct Length:When sizing an exhaust fan that does not open directly to the outside but is ducted, it isimportant to ensure that the exhaust fan has the capability to move stale air throughout theduct and ultimately to the outside. Here, we first need to understand what static pressure

and equivalent duct length is.Static Pressure: Inside every duct, there is a constant pressure being exerted at any point

from all directions. When an exhaust fan moves air through the duct, the air counters

resistance from this pressure which is known as static pressure. Thus, an exhaust fan has tohave the ability to overcome the static pressure in a duct so as to effectively duct stale air

to the outside of your home. This can be done by calculating the equivalent duct length ofany duct.Calculating Equivalent Duct Length (EDL): Simply measuring the length of a duct is not

enough to know how much static pressure an exhaust fan has to overcome. Ducts may have

one or more elbows, turns, or wall caps which add to the static pressure in a duct. Thus,you have to calculate the equivalent duct run and not the actual duct run so as to size an

exhaust fan properly.The static pressure in any duct run differs according to the material of the duct, number ofelbows and turns, exterior wall cap and wall jacks etc. Listed below are the standard values

for different duct components. Smooth metal duct: Actual duct length x 1 Flex aluminum duct: Actual duct length x 1.25 (for 4diameter duct)

Actual duct length x 1.50 (for 6diameter duct) Insulated flex duct: Actual duct length x 1.50 (for 4diameter duct)

Actual duct length x 2.00 (for 6diameter duct) Wall caps and roof caps: 30 feet for each cap (for 4diameter duct)

40 feet for each cap (for 6diameter duct) Elbows and turns: 15 feet for each (for 4diameter duct)

20 feet for each (for 6diameter duct)Using the above values, you can calculate the equivalent straight duct length that an

exhaust fan has to overcome so as to push stale air outside your home and counter staticpressure effectively.This ventilation guide is provided as a service from R.E. Williams Cont. Inc. Please beaware, that building codes and local regulations differ from region to region, they also canchange.; therefore, R.E. Williams Cont. Inc. assumes no liability for omissions, errors or the

outcome of any home improvement project. You should always exercise reasonablecaution, follow your current codes and regulations that may apply, and if in doubt on anyprocedure consult with a licensed professional.For a complete line of residential ventilation solutions, visit our website atwww.REWCI.com
http://www.rewci.com/http://www.rewci.com/http://www.rewci.com/http://www.rewci.com/

Documents

92474754 Exhaust Fan Guide