Proper ventilation is important to protect your home from moisture damage during the winter and to reduce heat buildup during the summer.
Even if your home is very tight, some moisture will travel to the attic, where it can cause a lot of damage if it’s not vented outdoors; you’ll see problems such as wet insulation (which is ineffective), water stains on your ceilings and ice dams on the roof during the winter.
Your home needs at least two ventilation sources for circulating air though the attic. Vents high—at or near the top of the roof—and low—at the lower edge of the roof—let air circulate naturally.
At the top of the roof, you can use continuous ridge vents, static roof vents, gable end vents or wind-driven turbines. At the lower edge of the roof, install continuous soffit vents or several single vents in the roof overhang; make sure these vents aren’t blocked by attic insulation and allow air to circulate naturally.
Attics with a ceiling vapor retarder should have a minimum of one square foot of vent area for every 300 square feet of ceiling area. If your ceiling doesn’t have a vapor retarder, your attic needs twice the amount of vent area, or one square foot for every 150 square feet of ceiling area.
Good natural ventilation makes a power ventilator unnecessary for most homes. However, if you can’t get enough air flowing through your attic on its own, a power attic ventilator is an effective, but expensive, solution to solve moisture problems and cool an attic. The best place for a power attic ventilator is near the top of the roof on the side facing away from the prevailing winds. During the winter, a humidistat automatically starts the fan to remove moisture from the attic; during the summer, a thermostat starts the fan when the attic gets too hot.
Here are a few more home ventilating tips While keeping the air moving through your attic is the most significant ventilation issue in your home, there are some other things you can do to promote proper ventilation there.
- A basement usually doesn’t need to be ventilated, but a crawl space containing water pipes or other utilities does. Install vents that can be opened in the summer and closed tightly in the winter to reduce heat loss. You’ll need about one square foot of vent for every 150 square feet of floor in the crawl space. Vents at each corner of the crawl space provide the best air circulation.
- A whole-house fan can be a good substitute for air conditioning, reducing indoor temperatures by several degrees. All you do is open your home’s windows during the evenings in warm-weather months and start the fan to draw cool air into your home and expel warm air into your attic and out the attic vents. You can expect lower air-conditioning costs through the prudent use of this energy-saving system.
- Install an exhaust fan in each bathroom to remove moisture from morning showers or steamy baths, as well as putting one in the kitchen to vent moisture and cooking smells. Note that exhaust fans remove heated or cooled air as well as moisture and odors, so use them only when needed. When you go shopping, make sure the fans you buy are properly sized for the rooms in which they’re located and their planned usage.
Can your home be too tight?
Tightening up your home with caulk and weather stripping, installing insulation and sealing ducts to reduce energy costs will have a significant effect on the way your home operates, as well as your comfort. However, it is possible to get your home too tight, causing it to trap stale air and moisture inside. One sign that you do not have enough ventilation in your home is the appearance of condensation on walls, attics or crawl spaces.
In extreme cases, a gas furnace, gas water heater and other fuel-burning appliances can use more than their fair share of the air in your home for combustion, creating a negative air pressure inside and causing the appliances to back-draft. This can lead to a number of problems—including carbon monoxide poisoning and even death. The same thing can happen if you have a wood-burning stove, a fireplace or an attached garage where you let your car idle to “warm up.”
The smart thing to do is to have a blower test performed after you’ve completed all your energy-saving improvements to check the amount of fresh air coming into your home. If it’s not sufficient for healthy living, you can add an air-to-air heat exchanger to your heating and cooling system to bring in fresh air. In addition, hire a technician to check your furnace and water heater flues to make sure they’re drawing properly and sending combustion byproducts up their flues and out of your home. If they’re not working properly, you may need to have the technician add a fresh-air intake to these devices.
In the future—when you’re replacing the heating system in your home—choose a direct-vent sealed combustion furnace or install an energy-saving ground-source heat pump.
Buy a carbon monoxide detector
To protect your family from carbon monoxide (CO) poisoning, have all fuel-burning heating appliances checked by a qualified heating contractor every year. And be on the alert for these signs of carbon monoxide poisoning:
- Your entire family is sick at the same time with flu-like symptoms such as headaches, nausea, fatigue and dizziness.
- Flu-like symptoms decrease while you’re away from home.
- Illness is present when gas appliances are in use.
- Excess moisture appears on the inside of windows.
Because carbon monoxide can’t be detected in any other way, buy at least one battery-powered CO alarm or an AC-powered unit with a battery backup for each level of your home and near sleeping areas. Other beneficial features include a digital display, which allows you to see both the level of CO as soon as it’s present and the memory of the peak level. This information lets emergency personnel know how high the level was—and how to treat victims of CO poisoning.
Follow the manufacturer’s directions for placement and installation. After you install your CO alarms, make sure you test them regularly. And when they’re ten years old, replace them. When a CO alarm sounds in your home, never ignore it. Get your family out of the house immediately, and open the windows to allow the CO to dissipate. Call emergency personnel from a neighbor’s home or a cell phone once you’re out of the house.
The material in this article was adapted from a new book, Home Tightening, Insulation and Ventilation, released by the Iowa Energy Center at Iowa State University. Besides offering much more detail on the topics discussed here, this book also covers how insulation can pay for itself in just a few years, talks about why ventilation is one of the keys to year-round energy savings and lists many sources of more information on energy efficiency and renewable energy topics. To get your free copy of this book:
- Download a PDF copy
- Call your utility company to see if you can stop by the office and pick up a copy;
- Request a copy by e-mailing the Iowa Energy Center at iec@energy.iastate.edu;
- Call the Iowa Energy Center at 515-294-8819 to ask for a copy by mail.