You can prevent mildew from living in bathroom

Home Work

September 06, 1998|By Karol V. Menzie and Ron Nodine

WHILE WE ARE on the subject of ventilation, as we have been recently, it's a good time to revisit the age-old problem of mildew in the bathroom.

Mildew likes the bathroom because it requires moisture to grow, and there is always lots of moisture there. So -- theoretically -- it's simple to discourage mildew from living on your walls and ceilings. You just reduce the humidity.

However, the problem gets more complicated when you start looking at the causes of the humidity.

When warm, moist air meets cold walls, condensation forms. The problem will be worse in winter, especially if there is little or no insulation in the walls.

Moisture gets into the air from a variety of sources -- taking a shower is the most obvious, but there are plenty of others -- bathing, cooking, doing laundry, even breathing are all activities that add to the humidity indoors. None of these are activities you can eliminate.

Humidity buildup became a more serious problem in houses during the energy crisis of the 1970s, when builders began sealing houses thoroughly to prevent air infiltration and loss of heat and cooling. The hot or cold air was sealed out, but the moisture got sealed in. There's actually something to be said for drafts.

If, however, you can't open a window, the next simplest way to get rid of moisture is to use a fan to exhaust it. Some modern building codes even specify fans, particularly in bathrooms.

If you don't have a fan in the bathroom, it's a good idea to get one. Fans themselves aren't expensive; most of the cost of installing one comes from running ductwork to the outside and connecting the fan to electricity. You might also consider installing a fan in the kitchen -- a range hood, for instance -- if you don't already have one.

Once you have the fan in place, the trick is to use it.

In the bathroom, turn it on before you turn on the shower and let it run a while after you turn the shower off. In the kitchen, use the fan while you are cooking. A whole-house fan can also help alleviate mildew problems.

In addition, there are products on the market designed to help with mildew problems. Some work better than others. Ron has a mildew problem -- two different kinds living in his bathroom.

On the wallpaper border, he gets what looks like transparent brown spots about the size of a quarter. The caulk joint around the shower is the home of the black-spot kind.

However, nothing grows on the painted walls or the woodwork. What does that tell us?

The paint is mildew-resistant, and it works; the caulk and wallpaper are not. How did this happen? Ron had the work done while he was on vacation, and while he specified what paint to use, he didn't specify the type of caulk. So the painter just used whatever he had. (This is another lesson in getting every detail into the specifications for every job.)

If you want to repaint or recaulk with mildew-resistant materials, be sure to clean and prepare the surfaces thoroughly. And don't forget to turn on the fan.

Ron Nodine is owner of American Renovator Inc., a Baltimore design-build remodeling firm, and current president of the Remodelors Council of the Home Builders Association of Maryland. Karol Menzie is a feature writer for The Sun.

If you have questions, tips or experiences to share about working on houses, e-mail Ron at or Karol at Or write c/o HOME WORK, The Sun, N. Calvert St., Baltimore, Md. 21278. Questions of general interest will be answered in the column; comments, tips and experiences will be reported in occasional columns.

Pub Date: 9/06/98

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