Keeping out the dampness. Left unchecked, excess humidity can create havoc in a house-rotting wood, peeling paint, and fostering rust and mildew. Keep your house well ventilated. Close windows on humid days and open them when the air is dry. If a closet or a room without a window is damp, install a vent, louvered door, or exhaust fan-or all three if the problem is severe. As a last resort, use a dehumidifier.
Install an exhaust fan in the bathroom, or open the window a crack whenever bathing. Install a hood vented to the outdoors over your kitchen range to carry off the water vapor created by cooking.
If you have a clothes dryer in a utility room or basement, check its connections and make sure that it is vented to the outdoors. Amazingly, the average dryer extracts a pound of water out of every pound of clothes. Attics and crawl spaces Warm, moist air, such as that generated in cooking, can seep into an attic. In winter it may freeze on the backside of roofing material, then thaw in spring and drip down to rot wood and saturate floor insulation, reducing its effectiveness.
If the insulation has no vapor barrier, install polyethylene sheeting under it or paint the ceiling with vapor barrier paint. Be sure your attic is properly vented. Cover crawl spaces with 6-mil polyethylene to keep water vapor from rising from the ground into the house.
House walls
Water vapor can penetrate interior wall materials and reach exterior walls, saturating the insulation or peeling exterior paint. Repaint the interior walls, using a vapor-resistant prime paint under the finish coat, or install tiny vents in the exterior siding to let trapped moisture escape.