It has long been said that you can cool your house down with a layer of white paint. The white paint is said to reflect more light and thus keep your house cooler than darker paint colors. Recently, companies have been producing heat-reflecting paint additives. These are chemicals that are mixed with paint to resist absorbing heat. You can buy them included in the paint itself or separately.
Choosing The Right Color
Choosing the right color is the first step in cooling your home down with exterior paint. The color that you see when you look at something is a result of the wavelengths that it reflects. If you look at green paint, for example, the pigment is absorbing every wavelength except for green. So, green paint will reflect green wavelengths. Black paint reflects no wavelengths; that means that it is absorbing the entire visible light spectrum. That’s why black paint heats up more than other colors. Therefore, it stands to reason that white paint, which reflects every color, will be the coolest.
Researchers tested this hypothesis by painting some examples of home siding with different colors of paint. They found that the boards painted with white paint were as much as 25 degrees F cooler than black boards. Therefore, your first step will be to choose the lightest color that you like. White will be the coolest but light yellow will be cooler than dark yellow and so on.
Heat-Reflecting Additives
The verdict is less clear on heat-reflecting additives. The research seems to suggest that when combined with white paint, heat-reflecting additives have very little effect. White paint already rejects most heat through the visible light spectrum. However, if you want a darker color, heat-reflecting additives have been found to do some cooling. A blue wall with additives will heat up less than a blue wall without the additives.
At the far end of the heat-reflecting paint spectrum is a new type of paint that has been developed for use in laboratories and near-earth orbit. The paint is actually made with molecules that respond to light by releasing their own energy. Early research has found that the paint actually cools down as more light hits it; that means, during the summer, your walls will actually be cooler than they are during the winter. Currently, it’s being used to paint roofs. Since the roof takes the most direct light, this is the most useful application of an experimental paint.
You should be on the lookout for these cooling trends to come to home painters near you soon.