What is the best exterior paint to resist mildew?

Mold and mildew growth on exterior surfaces is a common problem, especially in humid climates. When moisture gets trapped behind paint, it creates the perfect environment for mold and mildew to thrive. The constant moisture leads to peeling, cracking, and discoloration of the paint. Homeowners often find themselves repainting exterior surfaces frequently to cover up unsightly mildew stains. Choosing a mildew-resistant exterior paint can help prolong the life of the paint job and prevent the growth of mold and mildew.

What causes mildew on exterior surfaces?

Mildew grows on exterior surfaces when the following conditions are present:

• Moisture – From rain, sprinklers, humid air, etc that gets trapped behind the paint film.
• Heat – Mold thrives in temperatures between 70-90°F.
• Nutrients – Mildew feeds on materials found in paint such as oils, pigments, and binders.
• Lack of sunlight – Shady and poorly ventilated areas provide an ideal environment for mildew.

Mildew spores are always present in the air. When the spores land on a surface with the right conditions, they grow into mildew colonies that appear as black, grey, or green spots. Over time, mildew deteriorates the paint film and leads to premature paint failure.

How does mildew-resistant paint work?

Mildew-resistant paints contain special additives that inhibit the growth of mold and mildew on the painted surface. The additives used include:

• Zinc oxide – Inorganic compound that has natural antimicrobial properties.
• Copper oxide – Also acts as a fungicide that makes the paint film inhospitable for mold.
• Sodium/potassium borates – Prevents mold from metabolizing and spreading.
• IPBC (3-iodo-2-propynyl butylcarbamate) – An organic biocide that kills mold and mildew.

These additives prevent mildew from establishing by interfering with its reproduction and ability to spread. While the paint film may still get discolored over time, the growth will be minimal compared to standard exterior paints.

What features to look for in mildew-resistant exterior paints?

When shopping for a mildew-resistant exterior paint, look for the following key features:

Mildewcide Additives

Check that the paint contains mold-inhibiting additives like zinc oxide, copper oxide, or IPBC. The higher the concentration, the better the resistance.

Breathability

The paint should allow surface moisture to escape rather than trapping it behind the paint film. Breathable paints include masonry and elastomeric paints.

Ease of Cleaning

Choose exterior paints with “dirt pickup resistance” – they stay cleaner longer. Also pick mold-resistant paints that can be easily cleaned without damaging the paint film.

UV Resistance

Exterior paints should contain UV-resistant pigments that prevent fading, yellowing, and breakdown from sunlight exposure.

Mildew Warranty

Reputable mildew-resistant paints come with a minimum 10-year mold and mildew warranty against growth on the paint film.

How should you prepare surfaces for mildew-resistant paint?

Proper surface preparation is key to getting the most benefits from mildew-resistant exterior paints. Here are some tips:

• Clean surfaces thoroughly to remove existing mildew – Scrub with detergent and water, then rinse.
• Kill mildew spores – Use a mildew remover or bleach solution.
• Remove loose paint – Scrape off any cracked or peeling sections and sand surfaces smooth.
• Fill cracks and holes – Caulk gaps and prime exposed areas before painting.
• Pick ideal weather – Paint when temperatures are between 50-90°F and humidity is low.
• Allow proper drying time – Let the first coat dry completely before adding another coat.

Proper prep removes moisture sources, kills existing mildew, and allows for maximum paint adhesion so the mildew-resistant additives can work most effectively.

What are the best exterior paint brands for mildew resistance?

Here are some top exterior paint brands recognized for their mildew and mold-resistant formulations:

1. Behr Premium Plus Ultra

Behr’s Advanced Nano-Guarded Technology and anti-microbial agent provide long-lasting protection against mold, mildew, and algae. It’s a high-quality acrylic-latex paint available in thousands of colors.

2. Benjamin Moore MoorGard

This line of Benjamin Moore exterior paints is formulated with an EPA-registered mildewcide to resist mold and algae growth. It is available in low-lustre, semi-gloss, and high-gloss sheens.

3. KILZ Exterior Siding, Fence & Barn Paint

KILZ paint contains an antimicrobial package and 100% acrylic latex polymer to inhibit mildew growth. It self-priming, low-VOC, and fast-drying.

4. PPG Sun Proof Exterior Paint

Available in satin, semi-gloss and gloss finishes, this paint uses anti-microbial technology and UV absorbers to prevent mildew and protect surfaces. It can repel water and stains.

5. Sherwin-Williams Resilience

This premium latex exterior paint resists moisture damage and has very good anti-microbial properties to minimize mildew and algae growth on the paint film. It provides long-term durability.

How much does mildew-resistant exterior paint cost?

On average, you can expect to pay $30-$70 per gallon of mildew-resistant exterior paint from leading brands. Here’s a price comparison:

Brand	Product Line	Cost per Gallon*
Behr	Premium Plus Ultra	$46-58
Benjamin Moore	MoorGard	$50-68
KILZ	Exterior Paint	$30-40
PPG	Sun Proof	$40-65
Sherwin Williams	Resilience	$67-98

*Prices vary based on sheen, quality, and retailer. Premium lines cost more.

The investment is well worth it given the durability and longevity of these mildew-resistant exterior paints. With just one extra coat applied correctly, you can go 5-10 years before needing to repaint. This saves time, money, and hassle in the long run.

What are the limitations of mildew-resistant exterior paints?

While mildew-resistant exterior paints can inhibit growth, they have some limitations:

• Not mold-proof – Mildew additives deter but don’t completely prevent mold.
• Higher cost – Mildew-resistant paints cost 20-30% more than regular exterior paint.
• Reapplication needed – Protection reduces over time so reapplication every 5-10 years is required.
• Damaged areas prone to mildew – Any cracks, holes, and wear expose unprotected surfaces.
• Not a substitute for proper prep – Surfaces still need thorough cleaning and priming.
• Darker colors more prone to mildew – Lighter paint colors resist mildew better.

The paint can only do so much if underlying moisture issues are not addressed. Proper prep work, maintenance, and reapplication are still required for maximum mold and mildew prevention.

Conclusion

Mildew-resistant exterior paint provides the best defense against mold, mildew, and algae growth on exterior building surfaces. When combined with adequate surface prep, proper application, and periodic recoating, these paints can minimize ugly mildew stains. Although they have limitations, the enhanced durability, longevity, and protection they provide make these paints well worth the investment for homes in humid climates and areas with heavy mold and mildew growth. Leading brands like Behr Premium Plus Ultra, Benjamin Moore MoorGard, and Sherwin Williams Resilience offer great mildew resistance without the harsh smells and vapors of traditional oil-based paints. For prolonged exterior paint protection, mildew-resistant latex paints are the top choice to resist ugly mildew stains.