Ventilation
What it is
Filtration can be an effective supplement to source control and ventilation.
Improved ventilation: Bring in fresh air to dilute indoor pollutants and exhaust them to the outdoors.
Bathroom and kitchen fans that exhaust to the outdoors also increase ventilation and help remove pollutants.
HVAC systems should be checked routinely because mold in a ventilation system may be spread throughout the building.
Any fuel-fired appliance can be a source of carbon monoxide, especially if it is without adequate ventilation or improperly installed, maintained, or operated.
Its parts
- Exhaust fan
- Many older homes are equipped with kitchen and bathroom exhaust fans. While these fans provide intermittent ventilation to remove contaminants near the source, whole-house ventilation is intended to operate continuously (or at automated intervals) to provide dilution of potential contaminants across the whole house.
- Regardless of what kind of ventilation system you have for the rest of the house, exhaust fans are recommended in the bathrooms to provide local exhaust to remove excess moisture, cleaning chemical fumes, etc.
- Range hood
- More often, kitchen ventilation is provided by a range hood. Such hoods can often collect and remove cooking byproducts better than ceiling or wall-mounted fans (Singer and Delp 2010). In addition, range hoods are often equipped with grease filters that protect and extend the life of the fan itself.
- Where installed in accordance with the manufacturer's instructions and where mechanical or natural ventilation is otherwise provided in accordance with Chapter 4, listed and labeled domestic ductless range hoods shall not be required to discharge to the outdoors.
- Many range hoods (such as the one in Figure 5) can either be connected to an exhaust duct or recirculate the air into the kitchen. Exhausting air to outdoors is strongly recommended; recirculating air removes few contaminants and does not comply with most ventilation standards.
- Makeup air
- In larger buildings, ventilation systems often include active makeup air systems to balance air exhausted from buildings. Newer residential codes are also starting to require makeup air in some cases. In the 2009 IRC, for example, any local exhaust fans with capacity of 400 CFM or higher must include make-up air provisions (ICC 2009).
- Ventilation systems, including exhaust-only systems and improperly balanced ERVs and HRVs, can depressurize a home, pulling more air from the home than is brought into the home. Wind and stack pressure can contribute to house depressurization. Large range hood fans, clothes dryers, and fireplaces also contribute to depressurization of the home if makeup air is not provided.
- Natural-draft water heaters are susceptible to back drafting. This occurs when other things in the home such as exhaust fans and clothes dryers pull air out of the home, depressurizing the home. If the heated flue doesn’t have enough draw and there aren’t other adequate sources of makeup air for the flue, the flue emissions can spill back into the home.
- Dryer vent
- Domestic booster fans shall not be installed in dryer exhaust systems.
- Fire dampers, combination fire/smoke dampers and any similar devices that will obstruct the exhaust flow shall be prohibited in clothes dryer exhaust ducts.
- Whole-house fan
- A whole house fan is capable of pulling large quantities of air from the home and, particularly if not enough windows are open, may easily backdraft a water heater located inside a louvered closet door.
Related pages
- Glossary: Ventilation
Its entry, and the guide's pages that use it.
Sources
- U.S. EPA. Guide to Air Cleaners in the Home.
- U.S. EPA. Factsheet: What is Indoor Air Quality?
- U.S. EPA. Care for Your Air: A Guide to Indoor Air Quality.
- U.S. EPA. Mold Course Chapter 9.
- U.S. EPA. Carbon Monoxide Poisoning: Protect Your Family and Yourself Factsheet.
- U.S. Department of Energy. Whole House Ventilation Strategies for Existing Homes.
- U.S. Department of Energy. Bathroom Exhaust Fans.
- U.S. Department of Energy. DOE Building America Measure Guideline: Selecting Ventilation Systems for Existing Homes.
- UpCodes (code text). Chapter 5 Exhaust Systems, Illinois Mechanical Code 2021.
- U.S. Department of Energy. PNNL Building Science: Look for Signs of a Gas Water Heater Backdrafting.
- U.S. Department of Energy. Whole House Fan: How to install and use a whole house fan (U.S. Department of Energy technology fact sheet, DOE/GO-10099-745).