The size of an exhaust fan is measured in terms of its sweep (the diameter of the fan blades) and its air displacement capacity, which is typically measured in cubic feet per minute (CFM). The larger the room or area you need to ventilate, the higher the CFM rating you'll require.
Step 1: Measure the Room Size
To determine the right exhaust fan size, the first step is to measure the size of the room where the fan will be installed. For Indian homes, exhaust fans are most commonly used in bathrooms, kitchens, and sometimes storerooms.
Small Rooms (e.g., bathrooms): Typically around 6 to 8 feet in length and width.
Medium Rooms (e.g., kitchens): Around 10 to 12 feet in length and width.
Large Rooms: Any room larger than 12 feet in either dimension would be considered large.
Step 2: Calculate Required CFM
The general rule for calculating the required CFM for a room is based on its square footage. For every square foot of space, you'll need at least 1 CFM. In practical terms, for a typical Indian bathroom of 6×8 feet (48 square feet), you'll need an exhaust fan that provides at least 48 CFM.
In India, where kitchens often involve heavy cooking with oil, spices, and steam, the required CFM tends to be higher. For a medium-sized kitchen, 100 to 200 CFM is ideal to ensure effective removal of cooking fumes and odours.
Step 3: Refer to the Size Chart
Here's a quick size guide based on room size:
Bathroom (up to 50 sq. ft): 4–6-inch exhaust fan, CFM 50–100
Kitchen (up to 100 sq. ft): 6–9-inch exhaust fan, CFM 100–200
Large Rooms (above 100 sq. ft): 9–12-inch exhaust fan, CFM 200+
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