Here’s What Happens to Rooms That Get Exposed to Direct Sunlight


We’re always looking for easy, natural ways to stay healthy, especially during cold and flu season. From home remedies like wearing cold socks to bed to cocktails that double as cough syrup, we’re prepared to keep our immune systems working at their peak performance.

Besides keeping our immune systems in tip top shape, we’re also looking for ways to eliminate germs from our homes, and it turns out that there’s an easy way to do this…almost too easy. What do you have to do? Open the curtains.

In a recent study at the University of Oregon, researchers compared the effects of sunlight, UV light and darkness on dust that came from real homes in Portland. They extracted dust from these homes and transferred it to dollhouse-size rooms that they left outside while keeping the inside temperature in each room a normal, consistent inside temperature.

One room was kept dark. One room was only exposed to ultraviolet light. One room was exposed to daylight through regular glass windows.

Researchers tested the dust in the miniature rooms after 90 days. Why 90 days? That’s how long dust can hang around inside your house…even if you vacuum.

Researchers were surprised at what they discovered after analyzing the bacteria in the dust. Twelve percent of the bacteria in the dark room was viable bacteria (bacteria that’s able to grow), while only 6.8% of the bacteria in the room exposed to daylight was viable, and just 6.1% of the bacteria in the room exposed to UV light was viable.

UV light has already been known to be a great disinfectant. In fact, it’s used to clean drinking water. Ashkaan Fahimipour, lead author of the study and a postdoctoral researcher at the University of Oregon’s Biology and the Built Environment Center, was surprised that the daylight performed so similarly to the UV light.  

Most glass filters out UV light, so even without the UV light, the daylight was an effective way to kill germs.

We already knew that daylight was an effective way to keep the winter blues away and save electricity by keeping indoor lights turned off during the day. Now we know that daylight can also help us stay healthier by cutting the number of germs in our homes and offices in half.

Excuse us while we go open the curtains in every single room in our home.

Are you going to let daylight in your home more often?