July 9, 2009
“Indoor air is on average seven to ten times more polluted than outdoor air.” ~United States EPA
We try to contain indoor air as much as possible. We pay to heat it and cool it, why would we want it leaking outside. Newer homes, of course, are tighter than older homes.
But by limiting fresh air to enter our homes, we are in fact creating a pollution problem.
Indoor air pollution comes from a variety of places: radon from the ground leaching into our basements, formaldehyde out-gassing from furniture and carpet, particulates from the breaking down of biological matter, and gasses from household cleaners and chemicals—not to mention odors and moisture that encourages mold and mildew growth. When we limit the passage of air between the indoors and outdoors we are harboring these contaminants.
Vents in the kitchen and bath are excellent at expelling odors and moisture to the outdoors. When running, they are also removing indoor pollutants. This exchange of air is very healthy for your home and for you.
When air in your home exits through a vent, replacement air needs to be available to make up what is lost. This make-up air can come from an open window, leaky doors, down-drafting of a chimney or a recovery system specifically put in place to exchange household air. If your home is well sealed, you may find the operation of your vent fan disappointing. If replacement air is not available, a vent fan will starve for air. Not only will it not perform well, but it may prematurely age the motor.
A vent will also under perform if it is not clean. We recommend vacuuming your bathroom vent fan when cleaning. In the kitchen, clean or replace your grease filters often. These filters are in place to keep grease from building up in the ducts in your walls.
Determining what size vent you need for your application can be a complex calculation that takes into account not only the size of the room but also the length of the ductwork for your vent. Vents are sized by “cfm” (cubic feet per minute). For example, this simply means if you purchase a 100 cfm bathroom vent fan, this fan will replace 100 cubic feet of air per minute.
There is a caveat however, and this lies in your walls or your ceiling. The material, length and twists and turns that your vent ductwork takes as it sends the expelled air to the outside will have an effect on the efficiency of your vent motor. If the complete venting system is not accounted for correctly, you could find your 100 cfm vent fan only pulling 40 to 60 cfm – and if you don’t have adequate makeup air to replace what is being expelled that number gets even lower.
The manufacturer’s website and paperwork that comes with your vent fan should help you with your calculations to insure a proper installation. There are other independant websites that offer the formulas as well. If in doubt, hire a professional to assess the size of the room and what it will take to properly get the air to the outside.
The other important factor when buying a vent fan is “sones.” Sones rate how loud a fan is, the lower the sone – the quieter. However, lower sones also usually equate to a higher price tag. It may be worth the extra money however if you will be running the fan often or if you have sensitive hearing.
Fresh air in your home not only smells better, but is healthier for you too. We all have experienced dank air from time to time, but if you are experiencing chronic issues with dank, musty or smelly air for which you cannot pinpoint a source, it may be a sign of a larger problem and an appointment should be made with a remodeling specialist.
Selections from this article will appear in Imperial Kitchens and Baths next newsletter mailing.
Written By Imperial Kitchens and Baths Designer, Stephanie Bullwinkel (CBD).