exhaust fans

Bathroom and kitchen exhaust fans provide basic ventilation and are an excellent way to avoid moisture and odors. Be aware, however: since exhaust systems removes stale air from homes, they create negative pressures within the house, which should be compensated.

Moisture & Exhaust fans

Bathroom and kitchen exhaust fans remove moist air, and helps prevent and solve problems like mildew, mold and odors. You just need to run the exhaust fan during your showers, baths and cooking, and some minutes after them.

Every home should have a high-quality exhaust fan in each bathroom and in the kitchen, duly ducted to outdoors, even if it has a Heat Recovery Ventilator (HRV) or a Energy Recovery Ventilator (ERV) system.

Exhaust Fans and Home Insulation Levels

Since exhaust systems removes stale air from homes, they create negative pressures within the house. New fresh air should be brought into the home, which is often accomplished through air leaks. That is: exhaust systems work well in moderately air-tight homes. But, alone, they can't work well in superinsulated air-tight homes (unless there is another mechanical ventilation system).

Without a way of bringing fresh air into the house, exhaust systems can't work properly and are dangerous. They even can cause backdrafts, a rare but dangerous situation.

Backdrafts

Backdrafts happen when gas, fuel or wood combustion appliances compete for air with exhaust fans. Exhaust fans may pull the combustion gases back into the rooms and living space, creating air pollution and potentially very dangerous situations. To avoid them, homes should be moderately airtigh (which is common and not necessarily bad in moderate climates) or should use fresh air supply systems (mechanical ventilation). Obviously, the late solution is the better one, and the only truly solution, in cold climates and hot humid climates.

Exhaust Fans and Climate

In climates where energy efficiency and comfort demand highly insulated and air-tight buildings (cold climates, hot humid climates...), exhaust systems should be complemented with other mechanical ventilation, able to provide fresh air to the house and compensate the stale air removed by exhaust fans.

See: Mechanical Ventilation Systems

Central Exhaust Systems

Besides simple bathroom and kitchen exhaust fans, there are also central exhaust-only systems. These central ventilators are often installed in attics, crawl spaces and basements, with their ducting leading to bathrooms, kitchen and other rooms.

Central exhaust systems are reliable, cheap and very useful systems, able to extend the role of simpler systems. However they do not replace spot ventilation, that is, the bathroom and, namely, the kitchen room exhaust fans. It's usually advantageous or necessary to have also separate kitchen (and bathroom) exhaust fans, since central exhaust systems aren't designed to respond to specific room needs or designed to accommodate the grease associated with the kitchen area.

Exhaust Fans

When shopping prefer a Energy Star or other officially labeled exhaust system. To compare models, pay attention to the model's Recovery Efficiency (Sones) and the CFM (Cubic Feet per Minute). The best models are those with higher Sones and higher CFM.