Note: Last month we offered an overview of seven tips to keep your home healthy. This month we explore ventilation ways for your home to keep “breathing” safely.
What is ventilation and why does my home need to be ventilated?
Ventilation is the exchange of indoor and outdoor air. That may appear odd—after all, don’t we want to keep cold air out in the winter and warmer, humid air out in the summer? However, if your home is too well-sealed, it will also hold in harmful pollutants such as carbon monoxide and moisture that can damage your home as well as you and your family. To keep you safe, there must be a certain number of “air exchanges” between the outdoor and indoor air in your home.
These air exchanges are important in all homes, but especially critical if you:
- Have any combustion appliances (gas or wood furnace or fireplace, gas water heater or gas stove)
- Have an attached garage, as carbon monoxide from your garage will seep into your living area, especially if you run your vehicle to warm up in the winter before driving out of the garage
- Use any chemicals in cleaning, painting or other projects
- Have pressed wood furniture or cabinets which contain formaldehyde
- Have lead, which is found in older paint and pipes
- Have asbestos in floors or old insulation
- Have a high radon level (very common in Iowa)
- Have indoor pets or smokers in your home
- … The list can go on and on, so assume your home most likely has some harmful pollutants. Read more on the Environmental Protection Agency website.
How moisture fits in
Too much moisture also leads to major problems. Moisture can lead to mold and mildew, as well as rot wood and other building materials. Water comes into homes because of uncontrolled air flow where warm, moist air comes into contact with cooler temperatures, causing condensation. Sealing air leakage can help protect your home from moisture seepage.
Moisture is also created within your home through showering, washing and drying clothes, cooking, washing dishes, and more. Even breathing and perspiring creates moisture: the Department of Energy estimates that a typical family adds about three gallons of water per day to their indoor air.
For these reasons, moisture also needs to be vented out or removed in some way to protect your family and your home,
How to tell if you need more or less air exchange
Use your nose. If you can smell cooking odors, smell dampness, or if odors linger for hours or days, you may not have enough air going in and out of your home. If cooking smells don’t migrate to other rooms, your kitchen fan is probably doing a good job in that part of the system.
How to ventilate
There are three types of home ventilation:
- Natural ventilation, which is air movement from windows, doors and cracks in the home. This type of ventilation may still be common in older homes, but newer homes are built tighter and don’t allow for as much air leakage.
- Spot ventilation includes exhaust fans such as those in range hoods and in bathrooms. These are often used along with natural ventilation or whole-house ventilation, but may not be able to do the job alone. Word of warning: If your exhaust hoods do not vent to the outside, but instead go into an attic, you will be sending moist air into your attic insulation, which can simply move mold and moisture potential from one part of your home to another.
- Whole-house ventilation employs fans and ducting to exhaust stale air and/or bring fresh air into the house, providing controlled ventilation throughout your house. There are exhaust-only, supply-only and balanced systems that bring in and expel air.
Exhaust-only and supply-only systems can have damaging effects in certain climates and certain seasons. Too much moist air can be introduced into the home, creating moisture problems. During the winter, a supply-only system can over-pressurize the home and drive humid indoor air out through the insulation where it will condense on the cool outer wall or under side of the roof. In the summer, an exhaust-only system can depressurize the home, which can pull humid outdoor air into the wall and ceiling cavities, where it may condense and moisten the drywall. Exhaust-only systems can also pull in unwanted pollutants such as radon, that you don’t want in your home.
While balanced systems are the best option overall, they require a tight house and good engineering to work effectively. The system often includes a heat recovery or energy recovery ventilator (HRV or ERV) that improves efficiency and balances pressure by exchanging energy (from temperature and humidity) between outgoing and incoming air. In older homes, adding such equipment is often difficult and expensive.
How to ventilate and control moisture in older homes
While newer homes can effectively include mechanical ventilation systems, there are other tactics that may work better in older homes. These include the use of range and bathroom hoods (vented to the outdoors), opening windows periodically to refresh the indoor air (for example, opening windows at night to let in cool air and shutting them during the hot daytime hours during summer), running dehumidifiers in the summer and humidifiers in the winter to help with moisture control, and running a central air conditioner in the summer to remove moisture.