Out of sight, out of mind.
Let’s face it: Unless a problem arises — like a wet spot suddenly appearing on a living room ceiling — attics are pretty much ignored. So when a problem rears its head, leading to a trip to that forsaken spot, seeing dark, ugly stains on the rafters can come as a surprise. Clearly, the stains were caused by water saturating the wood.
But how did those stains get there? The roof sheathing is solid, the roofing shingles are relatively new, and there’s no obvious source of water infiltration. And yet there’s obviously a moisture problem. The next question is: How do you solve it?
First, let’s look at the source: In winter, moist air is transported from the heated area of the home into the unheated attic space, where it not only settles on the wooden rafters and plywood roof sheathing, but also melts the snow on the roof, leading to ice dams. On a cold day, you might even see frost on those wooden components.
The secret to a healthy attic keeping it the same temperature as outside! This is accomplished by a combination of ventilation and insulation. Attic vents will keep air circulating, and help keep humidity down. Fresh, cool air is drawn in through the vents installed in the eaves or soffits. Hot, moist air is expelled through the roof ridge or gable vents. Some vents include fans that move the warm air, but you shouldn’t have both systems at once, because that will defeat the purpose of expelling hot air.
Of course, the less moisture there is in the air that’s traveling from the heated home to the cool attic, the less moisture there will be to cause a problem in the first place. Excessive use of humidifiers and failing to use a bathroom fan that’s vented to the outside can contribute lots of unnecessary moisture to the attic dilemma. Keep the moisture in the house down, and the moisture in the attic will stay down as well.
The other factor in the healthy-attic equation is insulation. The goal of insulation in winter is to keep the house warm and the attic cool. The recommended level of insulation today for climate Zone 5 is R-49; that translates to about 13 inches of cellulose and 22 inches of fiberglass.
There’s another benefit to insulation: Not only will the living space stay warmer and the attic stay drier, but better insulation will cut heating costs, too. Stay warm, stay dry, save money. It’s a win-win-win answer to those ugly attic stains.