I've stated this many times now when I first bought the Dulux Exterior paint to compare to Black Widow. I also see that some folks are still recommending exterior paints. Bad idea!

Exterior paints contain many things that aren't meant for interior use. They contain mildicides, fungicides, pesticides, etc.

From Bob Vila:

One of the most important things to be aware of is that paint is formulated for either interior use or exterior use, and they have different properties: Interior paint is formulated for: Scrubbability and stain resistance; Good hiding ability; Splatter resistance; Easy touch-up. Exterior paint is formulated for: Color retention; Resistance to fading; Flexibility to withstand expansion and contraction due to weather; To provide a mildew resistant coating; Resistance to tannin bleed. Don't think that you should use exterior paints indoors on the assumption that it is "tougher". In fact, some of the highest-grade exterior paints can be worse to use indoors than a lower-quality interior paint.

From True Value:

Health Risks of Exterior Paint Used in Basement

Question:
What is the impact of using exterior paint inside? We used the True Value All Weather Exterior Paint on the inside of a basement. Should there be any difference in smell after 2 years? Is there any reason that this would be harmful? What is the difference between the interior and exterior paints? Is it a health problem?


Answer:
Exterior paint is not durable for inside use. It may chalk excessively and/or the paint would not stick to the surface if it needs to be repainted. Exterior paint also contains mildewsides/fungicides that may smell when there is high humidity. It can even pose a health hazard due to the greater concentration of these mildewsides that are not normally used inside. Exterior paint used indoors may also worsen allergies.

From Natural Handyman

Dear NH,
Is there any reason why I can't use exterior paint on the interior walls?
BM

Yes, there is. Exterior paint contains certain fungicides and UV protective additives that are not approved for interior use. Because of the extreme conditions exterior paints are designed to endure, the strength of the preservative chemicals used may be unhealthy in closed inside areas.

This begs the question, "Why do you want to use exterior paint inside your home?" If you are looking to get some of the qualities of exterior paint, such as mildew or water resistance, there are interior paints and additives that can do the job just fine.

For example, there are special bathroom and kitchen paints that have very durable, eggshell finishes plus tremendous mildew resistance. There are also additives, known as mildewcides, that are designed for interior use. They can be added to any paint, even flat ceiling paints and texture paints, to make them more "bathroom friendly" and mildew resistant.

And this from CIL:

Q: Can I use exterior paint inside?

A: We do not recommend that you use an exterior labeled paint for interior use. Exterior paints are designed for specific use on exterior surfaces, hence performance and film integrity may be compromised if used on interior surfaces. Additionally, exterior paints typically have included in their formulation mildewcides, to resist the growth of mildew on the dry paint film, and the level of mildewcide in the exterior paint may be above the level recommended for interior use.

From Lowe's:

When painting indoors, use paint marked as "Interior" or "Interior/Exterior." Exterior paint is not for indoor use. Plus it doesn't dry as quickly and has a stronger odor — an important factor inside the house.[/quote]

From House Painting Info:

[quote]Paints that are dedicated for exterior use have concentrated mildewcides and fungicides that could have heath risks if used indoors. Plus, exterior paints have more VOC’s, which means the paint will have a potent smell when compared to its interior counterparts.

Exterior paints, especially acrylics, are designed to fast dry and resist the worst that the environment can offer. Because of this, exterior paints won’t easily flow out smoothly on a surface and will more difficult to use. Many quality interior paints have the same great attributes as exterior paints without the health risks or problems of exterior paints.

I hope this helps keep people safe! Do not use an exterior paint indoors!

mech

These are obviously valid points but to be fair they are questions and answers that are completely out of context. We are talking about painting an area a fraction of the area that would normally be painted with interior paints in the context of home painting. I would whole heartedly agree that it would be ill advised to paint your home interior with exterior paints. Do keep in mind that many interior paints also contain these sorts of chemicals in smaller amounts.

According to the customer service representative at Behr, exterior paints are allowed, by law, to have a higher content of mildicides etc than interior paints. If someone knows the exact limits for each, interior vs exterior, we could easily do a calculation to see which is more dangerous, 50 square feet of screen surface painted with an exterior paint or 500 square feet of wall surface painted with an interior paint that contains these mildicides and fungicides.

No I do not recommend using exterior paints to paint the interior of your home.

Using Behr Exterior Ultra UPW 4850 for a screen, in particular a retractable screen, it is a good choice. Many of the attributes that make it a good exterior paint also make it an excellent paint for a flexible screen substrate.

Some even contain pesticides, UV protection chemicals, etc. The thing is is this. Everyone of the experts that had a comment on it says the same thing. Do not use exterior paints inside. And by recommending it here you're opening up a big can of worms for this site when a father of an asthmatic kid who uses your suggestion from here to use an exterior paint.

I even noticed that MississippiMan used an exterior paint in his trials and I can guarantee you he did not get that from us!

I would tread lightly when messing with health issues.

mech

I agree that everyone should thoroughly investigate matters when it comes to health issues. Whether it be UV problems/ pesticides / paint / or chemicals.

Thanks for both of your input on this matter.