Back To Ventilation

Residential Ventilation Checklist

• Vent sources of moisture directly to the outside. This is especially important for the bathroom, which normally produces more moisture than any other room in the house, and for the dryer, which produces more moisture than any other appliance.
• Do not vent moisture directly into the attic. The last thing you want to do is put warm, moist air into the attic. In cold climates this can contribute to icing and resulting leaks.
• A whole-house fan is acceptable because of its usual location, installed in the attic floor near a gable vent, and because it is not directly connected to a source of moisture. The whole-house fan can help to remove cooking odors and can cool the entire house when it is not hot enough to turn on the air conditioning. Use caution: natural-draft heating appliances could be adversely affected by too much exhaust - products of combustion could be drawn into the house.
• If you cannot vent the bathroom directly to the outside, install the vent up through the attic and down through a soffit vent. This will prevent water from dripping back down into the vent as it would if you installed the duct straight up through the roof. Wire the bathroom vent to a timer switch, so that people can turn it on without having to remember to turn it off.
• Always vent the clothes dryer to the outside with a smooth-walled (do not screw into walls of duct), metal (not plastic) duct that is as short as possible. To prevent a house fire, check the duct for clogs regularly. Do not vent the dryer directly into the laundry room. This puts much too much moisture into the house.
• Kitchens should have a vent hood with an exhaust fan. The vent hood should have a back draft flap to keep out insects and cold air - but some cold air will inevitably seep in.
• Install ceiling fans to improve ventilation and distribute heat. To disperse heat properly, run the ceiling fan in reverse, so that it pushes warm air up against the ceiling and down along the walls, where people tend to sit.
• Do not block air intake vents for heating or air conditioning equipment. Blocking these vents will starve the equipment for air, causing it to run inefficiently.
• If your unfinished basement has windows, keep them closed on hot, humid days to prevent moisture from condensing on the walls continuously, all day long. Open the windows once the humidity drops below the natural humidity of the basement, so that moisture doesn’t build up inside.
• People, in their zeal to do a good job, sometimes pack insulation into the eaves, blocking the soffit vents, because they don’t know that the vents exist or don’t know what they are for. If you are installing insulation in the attic for the first time, do not cover the soffit vents with insulation.
• If your attic is already insulated on the floor, make sure insulation is not blocking the soffit vents. This is more of a problem for loose-fill, since wind can scatter the fill around. To prevent loose-fill from scattering and covering the soffit vents, you can install baffles between the rafters. You staple the baffles to the underside of the roof sheathing, and the baffles maintain 2 inches of ventilation space next to the sheathing.
• Wind coming through soffit vents can also push batt insulation up off the floor, causing cold airflow against the ceiling and cold spots high up on exterior walls. Baffles installed near the eave should also prevent this problem, by keeping the batts from flipping up and over.
• If you are going to install batts or spray foam between the rafters, you should extend the baffles all the way up to the ridge vent. This will keep the sheathing dry and prevent it from rotting invisibly behind the insulation.
• Likewise, when you insulate between the floor joists in the ceiling of an unconditioned basement or crawlspace, you should leave some space between the insulation and the sheathing (subfloor) to allow water vapor to escape.