How to keep MILDEW out of your CLOSET

Closet doors are meant to keep closed, right?  Unless you are Martha Stewart, it’s likely your closet doors don’t stay open very long–if they close to begin with!  The problem comes when humidity and closed doors combine for a stinky problem: mildew and mold.

We sometimes think that mildew is a less toxic form of mold, but it is still mold nonetheless.  Mildew is a subclass of mold that exhibits a white or gray, flat, powdery growth, while the rest of the molds can get more fuzzy and colorful.  Both release spores, but unlike other molds, mildew doesn’t penetrate surfaces and grow into the materials it lands on (though it can still cause cosmetic damage). Instead, it grows on top of flat surfaces and often collects in places like cardboard boxes or your vintage leather jacket in the closet.  Not good!  (What is Mildew, Really? The Difference Between Mold and Mildew)

Since we know that mildew is a form of mold, we know that it needs several things to grow: a food source (ie. leather, clothing, and dust in general), moisture (even excess humidity) and air (although stagnant air is best because lack of circulation keeps humidity at surfaces high).  So, the best ways to keep mildew at bay in closets is to:

• Clean out the dust and seal off any sources of dust

• Keep the humidity down and ventilate

• Store items for longevity and air circulation 

How the heck does dust get in the closet when the door’s closed?

Incredibly, some closets are like dust magnets.  If your closet is part of a tiled or vinyl floor area, dust bunnies can usually slide right under the door due to the slick surface.  If you have any penetrations in the ceiling (like a light bulb), then your closet may be part of a hidden circulation system where the framing in your walls conducts air currents throughout your home.  For example, closets near bathrooms may unknowingly supply air to the bathroom exhaust fan, if the fan’s ductwork is not sealed well in the attic or the lightbulb box is not sealed to the ceiling.  Then there are the closets that double as storage areas and HVAC equipment rooms.  If the HVAC unit is not sealed well, it just pulls air from the surrounding home into your closet.

1. Seal

The way to keep out the dust is to seal these small air passages: at the ceiling, remove the light fixture and either use a caulk gun (less messy) or a spray foam can with a straw (very messy, be sure to cover everything!)  to seal the electrical box to the drywall.  If the closet is an upper story, you may be able to do it from above in the attic with less mess, and sealing all the ceiling penetrations may help with dust house-wide.  If you notice a lot of dust forming on the floor, it may be worth caulking the baseboards to the floor (if it’s tile or solid-surface) to seal that up as well.

2. Clean 

Next, removing the dust should be part of a larger goal to store items properly so that cleaning will be easier and mildew will be less likely to form.  You’ll need a HEPA vacuum with brush attachments, and various storage containers.  If possible, empty the closet.  This will allow you to see all the walls and floor to see if there are any water leaks coming in that could be causing the mildew.  If not, use the vacuum to clean ALL the surfaces so you can get a fresh clean start!

It’s a great time to wash clothing and purge any items that you don’t use anymore by donating them.  Clean clothing is less likely to smell and deteriorate from body sweat and dust mites as well.

Stop right there!  If you had mildew in your closet before, you need to make ventilation changes to stop it from recurring.

3. Ventilate/dehumidify

Mildew sometimes forms in closets because of lack of ventilation.  The great thing about moving air is that it lowers the moisture content of surfaces that come in contact with it.  If the air is not moving, the moisture content of surfaces tends to equalize with the stagnant air, and over time, mold is able to grow.  Also, if your closet is located on the corner or north side of a building, the insulation in the wall may not be sufficient to prevent warm house air from causing condensation on the cold wall.   Here are some tips:

• Add a closet-sized dehumidifier or desiccant bag (see our article here for recommendations)

• Add a small fan to the light socket so air can continuously circulate

• If there is a gap at the bottom of the door, install a fan in the top of the door to pull air through the closet and exhaust it at the top (or better yet, through the opposite wall).

4. Refill the closet

Ok, you can start restocking the closet but remember this important point: maintain space between items so that air can freely circulate!  Don’t overstuff or compact items against the wall, either.  Wire shelving is great for maintaining circulation from top to bottom, too.

Storage containers matter, too–if possible, don’t use cardboard boxes because cardboard holds moisture, and it’s a favorite food for all kinds of pests: mold, roaches and silverfish like to eat it, and mice like to use it for bedding!  If you’ve cleaned and dried your clothing and excess bedding, packing them in clear storage bins is ideal so that you can easily see what’s in each.  For wool and moth-prone items, you can add cedar blocks to the bin to keep pests out.  These garment bags are great to keep dust off hanging clothes.

After mildew remediation, it’s important to check on your closet at least every few weeks until you’re sure that the changes are producing their intended effect: the ability to close the closet door without mildew taking root!