Effects of Painting In High Humidity On Exterior & Interior Paint
Humidity soaks your clothes and makes your hair a disaster, but it can also damage the aesthetics of your exterior paint. Humidity is one of the most common problems when applying exterior house paint. Ever walk out of your door and wonder if you’ve taken a wrong turn and ended up in a swamp? The summer humidity in the South has a way of doing that.
The good news is that humidity doesn’t have to prevent you from painting the exterior or a humid bathroom. It does require a few additional precautions, but it can be done. Here’s what you need to know about both interior and exterior painting in high humidity.
Humidity Can Cause Problems For Exterior Painting
Some exterior house painters have tried to paint in high humidity while using the wrong paint, resulting in a sticky finish. Wonder why? It’s simple science.
Most acrylic paints include water solvents alongside a few additives. For the paint to cure and form a hard surface, the water must evaporate. The same applies to mineral spirits, which are typically the solvent in oil-based paint.
Without getting too technical, high humidity prevents the solvents from evaporating. When solvent evaporation is too slow, paint additives can stain and disfigure the surface, a phenomenon known as surfactant leaching.
High Humidity Percentages
You can use exterior paints like Sherwin-Williams Latitude at higher humidity levels than most people think, but there’s still a limit.
The ideal humidity level for painting is between 40% and 50%. If you’re indoors, a dehumidifier makes it easy to attain that level. When you’re outside, though, it’s not as easy. Proper exterior paints allow you to paint in humidity of 80%-85%. Shorter periods of lower humidity at night and early morning allow the paint to dry, and this is how painters work around high humidity during the day.
Moisture Absorption When Staining Bare Wood vs. Painted Surfaces
Painting in higher humidity has far less effect when painting over a previously painted surface. Uncoated raw wood is far more susceptible to retaining moisture than coated materials. Therefore, you need the humidity to be as low as possible when staining raw wood. This includes decks, fences, wood doors, and ceilings. Staining from late morning to midday is best because the humidity is lower then.
The humidity levels above and the tips below work well for coated materials. When it comes to uncoated wood, it’s better to wait until a drier time of the year, like the late or early summer.
Tips for Painting in High Humidity
While it’s possible to paint at higher humidity levels than you may have thought, there are tips you should follow to make it successful. If not, you may have paint-curing issues that require you to strip it and start over.
To keep problems to a minimum, follow these tips.
Tip 1: Paint While the Heat Is Rising
Timing is critical when painting in humid conditions. In particular, monitor the temperature and avoid painting when it is too hot.
The best time to paint your house is a few hours before the day reaches its peak temperature. The peak temperature typically occurs in the mid to late afternoon, but you can check the hourly forecast to confirm.
If you start painting too early in the morning, the home may still retain moisture from overnight dew. If the dew point is high, aim to paint in the late morning. Late morning allows the condensation water to dry. As the temperature rises, it will help the paint dry and cure faster.
Tip 2: Test the Surface Moisture Beforehand
While we’ve been talking about air humidity, moisture in the material you’re painting will also affect the result. There are ways to test a surface before you start to ensure it is dry. If you’re painting uncoated wood, scuff-sand a small area. You want to be able to blow the dust away with ease.
You can test the moisture of a painted surface by scrubbing it with a rag to see if moisture is removed. We certainly do not expect homeowners to have access to one, but a moisture reader provides the most accurate results.
Tip 3: Paint In the Order the Sun Warms
To ensure your painting surfaces are as dry as possible, start in the area where the sun first hits in the morning. Generally, this means you will start on the east side of your house and work towards the west. Remember, the trees and other shade can affect your approach.
Paint for Bathrooms With High Humidity
Interior painting may require extra thought when it is humid, too. Your HVAC system might remove enough humidity from the air to create excellent painting conditions. Measure your home’s humidity and, if necessary, buy, rent, or borrow a dehumidifier, air mover, or high-volume fan while painting small bathrooms.
Don’t overlook humidity that isn’t related to the weather. Avoid using the shower or tub before or after painting a bathroom. It’s best to apply multiple thin coats when painting a bathroom in high humidity. Thin coats of fast-drying, zero-VOC paint will allow walls and ceilings to dry and cure faster.
The best paint for humid bathrooms is Benjamin Moore Aura Bath & Spa. Bath and Spa is the most moisture-resistant and dries quickly. The paint also resists water vapor and surfactant leaching, which can occur on interior walls, too.
Lower Humidity and Dewpoints During Early Fall
Aside from being one of the most beautiful times of the year, fall is the perfect time to escape the high humidity for painting. The temperature is moderate, and the weather typically has clear, sunny days. There are also fewer insects and no pollen to worry about entering your home.
Just keep in mind that the best time to paint does not mean a better paint job. Think of the word “best” as being synonymous with the most ideal. The fall season is always a perfect time for exterior painting, especially when the clouds clear and the humidity drops.
Getting a Great Paint Job in (Almost) Any Humidity
Conventional sources may advise against painting unless you’re in the ideal humidity range of 40% to 50%. Those of us who experience high humidity levels understand that those levels are simply unachievable or, at best, seldom. So, yes. You can paint in humid weather. Just make sure your painters know which exterior paints are suitable for it and the processes to reduce the risk of aesthetic issues.
Contact us today for your interior or exterior painting project or for more expert advice about painting in high humidity!
