Q: : Are the mold-resisting properties of such resistant paints purely chemical or also physical in nature? If chemical, how long will the properties last and when should I paint my bathroom again?

A: For the most part, mold resistant paints do so through chemical processes. Similar to many antimicrobial products, the paint contains mold prohibiting chemicals which impair a molds ability to develop. Without knowing a specific brand that you have an interest in using though, we can't offer much more advice. Your question about the longevity of the chemicals also varies from product to product. But in all honesty, you sound like someone who is absolutely sure that mold is going to attack your paints … and that isn't necessarily going to happen.

I assume that the pride you take in maintaining the bathroom carries through to the rest of the home. As such, you can probably do more to prevent mold growth through maintenance actions than through the use of mold-resistant paints. Mold grows freely in any environment containing air, organics (food), and water. Your maintenance on the other hand, can easily control two of those three factors.

Remove the organic compounds that mold can grow on. This includes cleaning dust, dirt, or debris (leaves, grass, etc.) from indoor areas. Control the presence of moisture on interior surfaces. This may be as simple as fixing leaks, or it may include running a bathroom fan for 5-10 minutes after you shower, which will remove excess humidity from the room.

Even though you can't see it, mold is growing somewhere in your home. It may be in small quantities on your clothes, your shoes, or your draperies. It may be settling on the carpet, just waiting for the right amount of moisture. The "ball is in your court" then as you can diligently control moisture and dirt indoors, which will inhibit the possibility that mold will occur.

So your question of when to repaint again is really dependent on your commitment. Your commitment to perform regular home maintenance may allow the paint to last 10 years or more. And in all honestly, you could get this kind of life from most any paint, regardless of whether it contained an anti-microbial compound or not.

- Travis West

Travis West is the president of Building Air Quality Inc., a Houston-based indoor air quality consulting firm. He can be reached at twest@baq1.com, or toll-free at 866-367-1177. )

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If you have a question for a mold expert, please send it to Brett Lyon, senior editor of construction.com at brett_lyon@mcgraw-hill.com.