Think about this for a second: The average house collects a staggering 40 pounds of dust each year. And let’s take a moment to remember what makes up dust: Pet dander. Dead skin cells. Dust mites. Insect droppings.

The surprising answer: Open your blinds.

How sunshine fights germs

In a study published last year in the medical journal Microbiome, researchers at the University of Oregon described setting up a series of miniature (and very dusty) rooms. For 90 days, some of these dollhouse-size areas were kept in total darkness while others received UV light. Then, the dust was collected and the bacteria within it sampled.

“We found that household dust exposed to ordinary daylighting contained smaller loads of living bacteria, compared to dust bunnies experiencing darkness,” explains Ashkaan Fahimipour, the study’s lead author and now a postdoctoral scholar in computer science at the University of California, Davis.

The researchers also saw shifts in the types of bacteria living in those dust bunnies.

“Bacterial communities from daylit dust resembled those found in outdoor air, in contrast to dust experiencing darkness, which more strongly resembled the microbiome of human skin,” Fahimipour explains.

While some of the germs we’re exposed to in our daily lives are harmless or even beneficial, others are potentially harmful.

“Which of these are being impacted by light exposure is still an open question,” Fahimipour says.

That means it’s too early to say that sunshine definitively has sanitizing superpowers, but “based on our current understanding, I think we can say that ordinary daylighting has the potential to inactivate living bacteria,” Fahimipour says.

It’s really not a stretch to believe that throwing open your drapes is good for you. Sun-loving scientists have already amassed plenty of research that supports the benefits of natural daylight. Read on for what sunlight can do for you.

Sync your body clock

“Natural light is a primary consideration for a healthy and happy home, because sunlight is a crucial modulator of our circadian rhythm, a cycle which encompasses brain wave activity and regulates hormone production, cell regeneration, hunger, and sleep cycles,” explains Nora Bouz, a well-being design consultant. “That in turn influences our mental, emotional, and physical health.”

Our bodies are designed to be in sync with nature, Bouz points out.

“We wake up when the sun rises, reach our highest level of energy when the sun is at its highest point in the sky, and wind down and go to sleep when it’s dark,” she says.

Boost your mood

“When we’re exposed to sunlight, serotonin, one of the hormones responsible for our high energy and feeling good, is produced,” Bouz says.

You can think of serotonin as your body’s natural antidepressant. If your brain doesn’t make enough, you’ll start to feel irritable and fatigued. In some people, this can lead to to seasonal affective disorder (appropriate acronym: SAD).

Keep you healthy

Your body relies on natural sunlight to make vitamin D, which regulates over 1,000 different genes in your body. This form of vitamin D isn’t really a vitamin, per se, so much as a hormone that may help prevent health issues ranging from osteoporosis and diabetes to heart disease and arthritis.

Help you be more productive

Next time you have a ton of work to plow through, sit by a window. A typical sunny day has a “color temperature” that’s been shown to increase alertness and efficiency. Natural daylight can also lessen eye strain, which may slow you down at your computer.

Heal your skin

Blistering sunburn from hours in the sun? Obviously bad. Low levels of UV radiation—like you get from light streaming through your window? Not bad at all. Research shows that a small amount of sunlight triggers the release of a compound in your skin that quiets inflammation. That could be helpful if you have a skin condition like eczema.

Save you money

“If you have sunlight illuminating your whole house, why would you ever turn on the light?” points out Brad Roberson, president of Glass Doctor, a Neighborly company.

In a recent study to see how much natural light can save on energy bills, Roberson says, experimenters found that in addition to energy, they saved on cooling and heating. The total annual savings? 22%.

If you do decide to let more light into your home, choose sliding glass doors with UV-blocking glass. Old windows can be replaced with insulated glass units, or IGUs.

“IGUs prevent heat transfer from the summer sunshine, while also keeping cool air from escaping outside,” Roberson explains.

You’ll maintain your desired house temperature—and you just might eradicate some germs and acquire a sunnier outlook.

Stephanie Booth’s stories have appeared in magazines such as Real Simple, Cosmopolitan, Glamour, and Psychology Today.