Guide

Mold in Closets and on Clothing

Why closets are the perfect trap

Mold needs a surface with enough moisture for long enough. A closet on an exterior wall assembles all of that without any leak being involved.

• The wall is cold. It is an exterior wall, often with less insulation than the rest of the room because of framing and the way closets get built
• There is no air movement. A closed door and a packed rail means the air in there is static, so humidity at the wall surface is higher than the room meter suggests
• There is no heat. Closets rarely have a register, so the space runs several degrees below the room
• The contents absorb. Cotton, wool and leather all take on moisture from the air and hold it
• Nobody looks. The back of a full closet goes unexamined for months

The mechanism is the one described on humidity and mold. A room reading a comfortable 50 percent relative humidity can be well above that at a cold surface with no circulation, because relative humidity rises as temperature falls. Mold responds to conditions at the surface, not to the meter in the middle of the room.

Diagnosing it before you treat it

1. Empty it completely and look at the back wall, the corners, the ceiling and the floor
2. Feel the exterior wall. Noticeably colder than an interior wall is the tell
3. Check whether the pattern follows the wall (condensation) or drips down from one point (a leak)
4. Put a hygrometer in there with the door shut for a few days and compare it against the room
5. Check for a pattern that appears in winter and improves in summer, which confirms condensation
6. Look above: a closet under a bathroom or under an attic hatch has other candidates
7. Check the exterior of that wall for grading, gutters or a downspout discharging at it

If it is worse after rain rather than in cold weather, it is not condensation and you are looking for water entry. See musty smell but no visible mold.

The clothes

Usually saveable

Cotton, linen, synthetics and most everyday washables. Brush off loose growth outdoors first so you are not putting it into the machine, wash normally, and dry completely. Sun and air help, both because ultraviolet is unkind to mold and because outdoor drying is thorough in a way a crowded wardrobe is not.

Harder

Wool, leather, suede, structured tailoring and anything with interfacing. These can often be recovered by a specialist cleaner, and telling them what they are dealing with gets a better result than not.

Not worth it

Anything that still smells musty after a proper wash and full dry has growth remaining in the fibre. Repeated washing rarely fixes what one thorough wash did not. Items with visible growth through the weave rather than on it are generally a loss.

Do not put anything back until the closet itself is fixed and dry. Returning a clean wardrobe to the conditions that ruined it is the most common repeat.

Fixing the closet

1. Clean the surfaces. Non-porous surfaces with detergent and water. Drywall with real growth may need removing rather than cleaning
2. Leave the door ajar, or fit a vented door. This single change fixes a surprising number of these
3. Pull the rail and the contents a few inches off the exterior wall so air can reach it
4. Stop packing it solid. Air needs a route between garments
5. Get the surface temperature up: insulate that wall properly if it is accessible during any other work, or leave the door open when the heating runs
6. Keep the house between 30 and 50 percent relative humidity through the heating season
7. A small dehumidifier or a low-wattage closet heater as a last resort, not a first one
8. Wire shelving rather than solid shelving, because it does not block airflow

What not to bother with

• Moisture-absorbing tubs. They pull a trivial amount of water compared with what a cold wall condenses, and they create the impression of action
• Cedar. It deters some insects. It does not control humidity or mold
• Air fresheners, which mask the signal you actually want
• Painting over growth on drywall. It bridges the surface, it does not remove anything, and it fails
• Bleach on drywall or wood, for the reasons on does bleach kill mold

If the same thing is happening behind furniture on exterior walls elsewhere in the house, the problem is house-wide humidity rather than that closet. Start at humidity and mold and preventing mold.

Common questions

Why only this one closet?

Almost always because it is on an exterior wall, often on a north or west elevation, and often with an uninsulated or poorly insulated wall behind the hanging rail. Packed clothing stops air reaching that surface, so it runs colder than the room and collects condensation.

Can mouldy clothes be saved?

Washable fabrics usually, with a normal wash and thorough drying, ideally outdoors in sun. Leather, suede and structured garments are harder and may need a specialist. Anything that still smells musty after washing has growth left in it.

Will a dehumidifier in the closet fix it?

It helps but it treats the symptom. The cheaper and more durable fixes are airflow and surface temperature: leave the door ajar, pull the contents off the wall, and stop packing it solid.