One of the lesser-known things that energy auditors check for when inspecting homes for energy efficiency is proper ventilation: In the attic, kitchen, bathrooms, etc. Ventilation is important because it controls moisture and promotes indoor air quality.
The most efficient house imaginable would look much like a Styrofoam cooler with no windows or other openings, but that would get moldy and mildewy very quickly. If you’ve ever accidentally left your cooler closed for too long after a camping trip without drying it out, you’ve experienced this firsthand. So how do you keep a house from building up too much moisture? You vent out the most humid air in the bathrooms and kitchen. Unfortunately, we see shortcomings in these vents all the time. See if you have any of these issues in your own home:
Kitchen vent not ducted: If you see auditors checking the cabinet above your vent hood or microwave, they are not looking for a snack; they are checking to see where the exhaust goes. If there is no ductwork going up and out, the kitchen vent fan is simply recirculating back into the room. In this case, holes could be cut into the cabinet and ductwork installed to vent smoky, smelly, humid air up and out to an exhaust vent in the roof, exterior wall, or soffit.
Bathroom fan venting into the attic: Bathroom air gets very moist from running hot water for showers and baths. You can get away with venting this humid air up into the attic if you have perfect attic ventilation, but attics rarely if ever breathe freely enough for this to work. It is better to duct your bath fans all the way out of an exhaust vent on the roof, through an exterior wall, or out the soffit to prevent mold from building up in the attic.
Bathroom fan ducted into soffit: This builder at least tried to vent this bath fan out to the soffit, but closer inspection revealed that the soffit itself was not vented (typical in a foam house with an encapsulated attic). If left alone, this would lead to some nasty mold growing in the roof overhang. This member has since installed proper soffit exhaust vents to correct the problem and avoid expensive repairs in the future.