Maintenance  Mildew Prevention/Control Mildew is actually a mold, carried by spores — which are nearly everywhere. They land on surfaces all the time — sometimes they "take" and grow and you have a problem. Mildew is unsightly. It suggested a lack of cleanliness and care. But mildew problems are more than aesthetic. Mildew can actually attack and degrade certain materials, eventually destroying them. Especially indoors, mildew can cause bad smells and aggravate allergy problems. How to stop mildew? First, know what mildew "likes" and avoid providing it. Mildew likes moisture, with relative humidity of 70 percent or higher, and temperatures between 77 and 86 degrees (although some kinds of mildew can occur from freezing temperatures to nearly 100 degrees). Finally, mildew needs to eat — the presence of some organic material, like soil, grease, or food (even stains can do). To deny these conditions and prevent mildew: Keep it clean. Use good maintenance practices inside and out. Control the climate. Indoors, use AC, fans, and dehumidifiers to keep the air out of optimal ranges. Outdoors, plan plantscaping with care. Don't create heavily shaded, closed-in areas that block air circulation and sunlight from your building's facade. Chemical mildew inhibitors and fungicidal sprays can also help in problem areas. When it's time to renovate, consider finishes with dirt-resistance. If mildew is a real problem in your area, there are finishes available with built-in mildewcide. For best results, combine mildewcide with dirt-resistant finishes.