Should you close blinds to keep heat in?
In the summer, you may want to keep window coverings closed to reduce heat gain. For natural light, open those window coverings that don't get direct sunlight. You may also want to try switching the ones that are opened and closed through the day to maximize light and heat from the sun when you want it.
Yes, blinds are good insulation for windows, regardless of the type of blind you use. This is because the closed blind forms a barrier (that is permeable to various extents depending on the blind), which helps to keep heat in, cold out, and to take the edge off draughts from rattly windows.
Sunshine streams in through the window, and the gap in between the window and blinds captures the heat, producing a greenhouse effect. In the winter, this is a desirable effect, and in the summer, when you want it to be cooler in your home, all you have to do is raise the blinds to leave the window uncovered.
During this research, one company found that drawing your blinds in the evening can reduce heat loss by as much as 14%. And, if you decided to pair your blinds with curtains, you could further reduce this by an additional 17%. So yes, closing blinds really does help you to save energy!
Blinds Down: Rounded Side Facing In
Tilting the blinds down significantly helps direct heat towards the center of the room, allowing you to optimally tap natural resources in the winter. During the hot summer nights, it allows warm air to escape outside, thereby helping you reduce your cooling costs.
“Generally, when it is really hot outside it is a good idea to keep windows closed during the daytime, as you don't want the hot external air to come into the house warming it up. However, after the sun goes down, the outside air will start to cool down,” Browning explains.
For the best effect you should pull up blinds during the day to allow sunlight in to warm the home. In the evening, as soon as the sun sets, the blinds can then be pulled down. With the blinds shut, warm air from the natural sunlight and your mechanical heaters won't escape from the home.
When completely closed, highly reflective blinds can reduce heat gain by around 45 percent, says the DOE. They can also be adjusted to block and reflect direct sunlight onto a light-colored ceiling, which diffuses the light without much heat or glare.
By closing the blinds, you keep direct sunlight out of your home and reduce unwanted solar heat gain. Closing window blinds help save energy in the winter since, during cold nights, heat is lost through windows. Closing the blinds will add some insulation to the windows, reducing heat loss.
While you may be focused on removing the dust in your home, according to an article published in Science Daily, letting the sunshine into your home through the windows can actually kill bacteria that live in the remaining dust and this can help decrease the risk of respiratory issues.
Should you keep windows and blinds closed in hot weather?
Chris added: "Much of the sunlight that enters your home through the windows turns into heat, so it's a good idea to keep your curtains and blinds closed, at least during the hottest times of the day. You may even want to opt for blackout curtains to keep windows covered and block the sunlight out completely."
Privacy: Blinds provide an effective way to control the amount of privacy in a room. By adjusting the slats or pulling them completely closed, individuals can prevent outsiders from seeing inside their homes or offices.

Privacy. They don't want people being able to look in windows and see them. This is especially true if your windows are a direct line of sight into a bedroom or bathroom, where people are generally naked or in the process of getting ready.
The correct way to close blinds is to lower them down to your desired position, then rotate the slats into a downward position. This ensures that they are completely shut and will provide maximum privacy and darkness.