Have you ever been told “There’s no difference between interior and exterior paint; it’s just a sales gimmick?” This is probably not true. (I say “probably” because some people do go overboard in trying to sell their products, and there’s no question there are poor quality paints out there.) Interior and exterior paints are exposed to totally different challenges, and it makes sense that they would be different. Any reputable paint manufacturer will produce two different products.

Exterior paints face an uncontrolled environment:

• They are typically exposed to marked changes in temperature so they must be able to expand and contract without splitting and cracking.
• They are exposed to water in the form of rain and high humidity in the air, so they have chemicals added to make them resistant to moisture, and to mildew and other fungi.
• Sunlight fades colours; exterior paint should be resistant to fading.
• Exterior paint gets maximum air circulation, so chemicals such as solvents, fungicides, and pesticides can be added in higher concentrations without fear of making indoor air unhealthy.

Used indoors, an exterior paint may dry too quickly to roll on nicely, and may smell unpleasant over a long period of time

Interior paint can be used in any controlled environment, where it will not be exposed to temperature changes, humidity, and direct ultraviolet light from the sun:

• Interior paint is designed to be washable.
• It is stain resistant.
• It hides flaws easily and is easy to touch up.

Interior paint will not stand up to the weather outside, and doesn’t damage indoor air quality as much. Formulations are available for high humidity areas such as kitchens and bathrooms, and for areas that need extra durability. These paints will perform better than exterior paint meant for a different purpose.

Remember that there are now environmentally friendly, hypoallergenic, and recycled paints on the market too.