Moisture in the Home

Homes these days are subjected to many sources of moisture. Bathrooms and kitchens are probably the worst. Bathrooms, of course, must have an exhaust fan in order to remove the excess moisture from the room. Exhaust fans are sized according to the maximum amount of moisture laden air capable of being removed. In most cases the fans are approximately 50-100 CFM (cubic feet per minute). In a standard size bathroom, 8'x5'x8' the maximum amount of "heavy" air in cubic feet would be 320 cubic feet. A fan capable of 100 CFM per minute will exchange all of the cubic feet of air in that room approximately every 3 minutes. A kitchen, however, presents several problems. First of all, kitchens are usually much larger than bathrooms. The extent of an exhaust fan is usually just an exhaust fan over the stove, or a range hood with a fan ducted to the outside. The amount of air exchanged with this type of set up is actually minimum compared to the amount of heavy air produced. Another producer of moisture laden air is the occupants in the building. The people living inside the home contribute to the amount of air needing to be exchanged. All of this is leading up to the need for an air exchanger. Air exchangers in homes reduce the amount of moisture laden air collecting inside the home and replace it with fresh air from the exterior of the building. We will do another posting on air exchangers soon. The only other problem with exchanging air in homes is that fans only work if people use them. An inspector will look to see that all the fans are functional, and that there are no traces of excessive moisture. He will use a moisture meter to determine the amount of moisture is in the air, in the walls, in the floors, and anywhere else it may be a problem. A good test then would be to test the air, run the fans for 15 minutes, and test the air again. Knowing the size of the fan is helpful. Make sure your inspector does a fan test and a moisture test of the interior air environment. Let me know in the comments if you have any questions. Until next time-A safe home has been inspected! -Inspector Tom