Most of today's new homes are extremely insulated and almost air tight. While this is great as far as cost productive power 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 discrete problems along with mold and mildew, health problems, ruined furniture, peeling paint etc. This is why it is important that you take every step to improve the capability of your indoor air, which can be achieved through mechanical ventilation.
An perfect way to ventilate your home thoroughly, efficiently, and cheaply is to install exhaust fans in your home. This report explains what exhaust fans are, their distinct types, how to settle on the best one for your home, and also the benefits of exhaust ventilation fans.
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What Are Exhaust Fans
An exhaust fan is a mechanical ventilation expedient that helps to draw out stale and impure air from your home and bring in fresh air, thereby enhancing the capability 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 Fans
Exhaust fans are classified into discrete types, generally depending on the type of mount and the location where you need to install the fans. The distinct types are:
1. Ceiling Mounted Exhaust Fans: As the name suggests, ceiling exhaust fans are those which are installed in the ceiling. Such fans expel stale air from your home upwards through the roof. The fan is associated to ducting, which is exhausted face the home via an external vent, like a roof cap or soffit exhaust vent.
2. Inline Exhaust Fans: Unlike ceiling exhaust fans that are installed directly into the ceiling, inline exhaust fans are typically mounted in-between ducting, hence the name inline fan. For instance, if you wanted to ventilate an area that did not have clearance or space for a ceiling mount fan, you would make use of inline exhaust fans to ventilate such areas. The exhaust fan would be placed in in the middle of the ductwork and the stale air would voyage through the ducts and finally be expelled from your home. Since inline fans are not mounted directly to the ceiling, they are very quiet. When installing an inline fan, to reduce noise, we suggest 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 in remote areas, they are also referred to as remote mounted exhaust fans. Inline exhaust fans can whether be single-port (exhausting from a singular area) or multi-port (exhausting from multiple areas).
3. Wall Mounted Exhaust Fans: These exhaust fans are installed on walls. Since they are installed on face walls of the home and not on interior walls, the stale air has a direct route to the face of your home and thus no duct work is required in installing these exhaust fans.
4. Combination Exhaust Fans: Exhaust fans are also ready as Combination units. You have the selection 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 in a singular device.
5. face Remote Mounted Exhaust Fans: While most other exhaust fans are installed inside your home and push stale air out, face remote mounted fans are installed face your home and pull out stale indoor air instead of pushing it out. The main advantage of these exhaust fans is that regardless of however noisy they are, most of the noise remains face your home.
6. Kitchen Range Exhaust Fans: These fans are mounted inside the range hood over your kitchen 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 any types of exhaust fans can be used for complete ventilation of your home along with 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 Fans
Exhaust fans are very productive at ventilating your home and other living spaces. Without proper 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 expanding to these pollutants, activities such as bathing, cooking, and washing also publish excess moisture in the air and make indoor air extremely humid. If not ventilated adequately, these added pollutants and increased moisture levels can decrease the capability of indoor air greatly, thereby important to discrete problems such as:
Health problems along with asthma, allergies, nose bleeds, skin rashes, headaches, nausea, and other breathing disorders. In fact, according to the Environmental protection Agency, a large division of the over 20 million each year asthma cases in the 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 enhancing indoor air quality, you can rid yourself and your home of all these problems.
Recommended Sizing Of Exhaust Fans
To ventilate your home effectively, it is important that the exhaust fan you pick has the capacity to exhaust the intended space completely. To ensure this, you must settle on the right sized fan for your needs. Here's a look at how to size exhaust fans properly.
1. Location of the Exhaust Fan and Air Changes Per Hour:
Where you intend to install the exhaust fan will have a direct bearing on its size. As per the Home Ventilating build (Hvi), distinct locations in your home wish varying Air Changes 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 amount of times the air should be completely changed in an hour. Thus, an 8 Ach advice for bathrooms means the exhaust fan should have the capacity to completely convert 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 conclude how large an exhaust fan you need (in other words, Cfm rating of the fan) here's what you need to do.
Sizing Bathroom Exhaust Fans:
First and foremost, part the dimensions (length, width, and height) of the room and then guess the volume of air in the room by multiplying all these 3 numbers. For instance, if your bathroom has dimensions of 6 x 10 x 8, then the air volume in the bathroom 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 Cfm rating for the fan which in this case is 64.
A simpler way of determining the Cfm rating for bathroom exhaust fans is to naturally multiply the 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 would be 60 Cfm.
However, if your bathroom is more than 100 sq. Ft. In size, you have to add the distinct fixtures in your bathroom to reach the desired Cfm rating. The recommended Cfm for distinct 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 gift the Cfm rating will growth 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 of your kitchen cooking range (if without range hood) or the size and location of the range hood if there is one. Here are the recommended Cfm ratings for kitchen range hood exhaust fans:
Generally speaking, for every 10,000 Btu of the range, it is recommended a minimum of 100 Cfm. So if your range is rated at 50,000 btu's, you would think 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 face but is ducted, it is important to ensure that the exhaust fan has the capability to move stale air throughout the duct and finally 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 to have the capability to overcome the static pressure in a duct so as to effectively duct stale air to the face of your home. This can be done by calculating the equivalent duct length of any duct.
Calculating Equivalent Duct length (Edl): naturally measuring the length of a duct is not adequate 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 guess 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, amount of elbows and turns, face wall cap and wall jacks etc. Listed below are the thorough values for distinct duct components.
Smooth metal duct: Actual duct length x 1
Flex aluminum duct: Actual duct length x 1.25 (for 4"diameter duct)
Actual duct length x 1.50 (for 6"diameter duct)
Insulated flex duct: Actual duct length x 1.50 (for 4"diameter duct)
Actual duct length x 2.00 (for 6"diameter duct)
Wall caps and roof caps: 30 feet for each cap (for 4"diameter duct)
40 feet for each cap (for 6"diameter duct)
Elbows and turns: 15 feet for each (for 4"diameter duct)
20 feet for each (for 6"diameter duct)
Using the above values, you can guess the equivalent straight duct length that an exhaust fan has to overcome so as to push stale air face your home and counter static pressure effectively.
This ventilation guide is provided as a aid from R.E. Williams Cont. Inc. Please be aware, that construction codes and local regulations differ from region to region, they also can change.; therefore, R.E. Williams' Cont. Inc. Assumes no liability for omissions, errors or the outcome of any home correction project. You should all the time rehearsal cheap caution, effect your current codes and regulations that may apply, and if in doubt on any procedure consult with a licensed professional.
For a complete line of residential ventilation solutions, visit our website at
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A Guide To Residential Ventilation Exhaust Fans
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