Bathroom exhaust fan is a must to vent out the hot moist air after a shower to save your bathroom from moisture and mold. A bathroom fan should have a timer instead of a switch to control it. The air should exhaust continuously for about 20 minutes after you have used the bathroom and a timer will save you from the cumbersome exercise of keeping an eye on the watch and remember to switch off the fan in the bathroom afterwards. These days bathroom fans are quieter and do not make so much noise and it is easy to forget to turn them off after the required run time. Choosing good bathroom fan means to determine that it is capable of achieving 8 air changes per hour and is size appropriate for your bathroom.

Determine the right size of fan for your bathroom by calculating the CFM (cubic feet per minute) of the bathroom, which means minimum airflow needed to achieve 8 air exchanges per hour. The formula to calculate CFM is:

CFM = Volume/7.5, where Volume = Length x Width x Height (of the bathroom)

Thus a bathroom that is 10 feet long, 10 feet wide and 10 feet high has:
Volume = 10 x 10 x 10 = 1000
And, CFM = 1000/7.5 = 133.33.
Thus, any fan with CFM listed as 134 or higher is good enough for this bathroom.

The noise level of the bathroom fan also plays a major role in its price and our budget. Though, everybody would love to have the quietest fan for their baths, the budget limit their choices to whatever is available within their budgets. The noise level of bathroom fans is measured in SONES. 4.0 Sones is the normal voice of a television, 3.0 Sines is office noise, 1.0 Sone is noise of a refrigerator and 0.5 Sone is the sound of rustling leaves. 3.0 and 4.0 Sones is quite loud for a fan but any fan at 1.0 Sone should do well enough in your bathroom. Install the bathroom fan correctly to keep its noise level down and use screws in its installation and not nails. Bigger venting with gentle turns means gradual venting and quieter fans. Sharp bends may cause more air noise while it is venting.

Looks of a bathroom fan should match with your bathroom decor. Fan may range from white and brown to several colors and they can have additions such as a light or a heating element. Premium bath fans look great while they protect your bath from moisture, steam and odors and provide proper ventilation in the bathroom and make it airy. Bathroom exhaust fans today are quite flexible in their designs and on fan can either be used to ventilate two bats or one remote fan motor can operate several exhaust grilles for effective spot ventilation in a single bath. For spot ventilation, ceiling grilles are mounted in the shower, over the toilet or over the whirlpool tub so that the moist air in the area can be dissipated quickly and efficiently.

Some of the high-end quality fans come with protective shell made up of UV-protected thermoplastic resin that can be mounted easily in wet locations. Smaller baths and powder rooms can use small-scale ceiling mount grilles with fan motor installed in a remote location, perhaps away from the bathroom. Fans with 'friendly flex duct' are easy and quick to install. One must always use insulated flexible duct to reduce the noise level of the fan and ideally, there should be at least 8 feet of flex duct between ceiling grilles and fan. Multiple ceiling grilles or ceiling grilles with lights make your bathroom airier and brighter. For luxury bathrooms and oversized baths, bathroom vanity fan with spot ventilation is best that keeps the bath free of mold and moisture.