Spring melt and wet cellars
Heavy snow melts in a few weeks, and the ground beside a foundation takes in that water. Older cellar walls let some of it through as damp patches, and the air in the cellar stays humid into summer.
Gutters that end at the wall and soil that slopes toward the house make it worse.
Older brick and stone
Brick row houses and stone foundations were built to breathe. When the mortar ages or a gutter fails, they take in water and hold it.
Cohoes and the older parts of Albany have many houses like this, and the damp often starts in one wall.
Cold windows in winter
Warm indoor air meets cold glass and leaves water on the sill. Over a whole winter that water soaks the frame and the wall below it.
Wiping the sill and running a fan in damp rooms helps more than most people expect.
Bathroom fans that do not do their job
A fan that vents into the attic instead of outside pushes steam into a cold space, where it condenses on the roof deck. A fan that is too small cannot move enough air.
A fan that barely holds a sheet of paper to the grille is worth replacing.
What to aim for indoors
The EPA suggests keeping indoor humidity below 60 percent, ideally between 30 and 50 percent. Source: US EPA, A Brief Guide to Mold, Moisture and Your Home.
A small humidity gauge costs a few dollars and tells you more than your nose does.
