When sunlight pours through a window, it can quickly turn a comfortable room into one of the hottest spaces in the house. Closing the blinds may help a little, but the glass, blinds, and surrounding area can still feel warm long after the sun moves away.

That leads to a common question: What can you put on windows to keep heat out?

The main options include:

• Solar control window film
• Exterior solar screens
• Awnings and exterior shades
• Cellular shades
• Blackout curtains
• Blinds
• Replacement windows with energy-efficient glass
• Trees and strategic landscaping

Each option works differently. Some block sunlight after it has already entered the home. Others reduce solar energy before it passes through the window. The right choice depends on how much heat you want to reduce, whether you want to preserve natural light, and how permanent you want the solution to be.

For many homes, professionally installed solar window film provides the best combination of heat reduction, visibility, appearance, and cost.

Why Do Windows Make a Room So Hot?

Windows allow several forms of solar energy to enter a home, including visible light, ultraviolet radiation, and infrared energy. Once that energy passes through the glass and reaches floors, furniture, walls, and other interior surfaces, it is absorbed and released as heat.

This is known as solar heat gain.

The National Fenestration Rating Council measures a window product’s ability to resist this heat using its Solar Heat Gain Coefficient, or SHGC. A lower SHGC means less solar heat passes through the window.

Heat can also move through a window by conduction. When the exterior glass becomes hot, some of that heat transfers through the window assembly and into the room. This is one reason an uncovered west-facing window can continue warming a room even when the air conditioner is running.

Windows have a significant influence on the energy performance and comfort of a building. The U.S. Department of Energy identifies reducing unwanted summertime solar heat gain as an important part of improving window performance.

The most effective heat-control products either reduce the amount of solar energy entering through the glass or prevent the sunlight from reaching the glass in the first place.

Solar Window Film: The Best All-Around Solution

Solar control window film is a thin, professionally installed material applied directly to existing glass. It is engineered to reduce the amount of solar energy that enters through the window.

Unlike ordinary plastic sheets or decorative coverings, architectural window films are designed specifically to manage sunlight. Depending on the product, a film may reflect, absorb, or selectively filter different parts of the solar spectrum.

The result can include:

• Cooler rooms
• Fewer hot spots near windows
• Reduced glare
• Better protection against ultraviolet radiation
• Improved daytime privacy
• Less strain on the cooling system
• Continued access to natural light and outdoor views

The International Window Film Association explains that window film can reduce heat entering through glass by reflecting or absorbing portions of the sun’s infrared and ultraviolet energy.

Window film is particularly useful when a home has windows that are structurally sound but allow too much heat into the room. Rather than replacing the entire window, homeowners can improve the performance of the existing glass.

Professional window film also works continuously. You do not have to remember to close it before leaving the house, adjust it throughout the afternoon, or reopen it when the sun moves.

Does Window Film Have to Be Dark?

One of the biggest misconceptions about residential window tint is that it must be dark to block heat.

Modern solar window films can be nearly clear while still reducing a meaningful amount of solar heat. Some products are designed to target infrared energy while allowing much of the visible light to pass through the glass. This means homeowners do not necessarily have to choose between a cooler room and a bright, open interior.

The International Window Film Association confirms that window film can appear visibly clear while still improving comfort, reducing ultraviolet exposure, and controlling glare. Darker films can still be appropriate when additional glare reduction or daytime privacy is desired. However, darkness alone does not tell you how much heat a product will reject.

When comparing films, look at performance measurements such as:

Total Solar Energy Rejected: The percentage of incoming solar energy rejected by the glass and film system.

Solar Heat Gain Coefficient: The fraction of solar heat that is allowed to pass through the window.

Visible Light Transmission: The percentage of visible light that passes through the glass.

A professional installer can compare these numbers and recommend a film that matches your comfort and appearance goals.

Exterior Solar Screens

Exterior solar screens are mesh panels installed on the outside of a window. Because they intercept sunlight before it reaches the glass, they can be effective at reducing solar heat gain.

They are particularly useful on windows that receive intense direct sunlight for several hours each day.

However, exterior solar screens have some drawbacks. They can darken the view, change the exterior appearance of the home, collect dirt, and require seasonal removal or maintenance. Their effectiveness also depends on the density, condition, and placement of the screen.

Solar screens may make sense when a homeowner wants an exterior solution and does not mind reducing visibility. For homeowners who want to preserve a cleaner view through the glass, window film may be more appropriate.

Awnings and Exterior Shades

Awnings, shutters, and exterior roller shades prevent sunlight from reaching the window. From a heat-control perspective, stopping solar energy before it strikes the glass can be highly effective.

These products can work especially well over windows that receive predictable direct sunlight. The disadvantages are primarily related to installation, appearance, operation, and cost. Exterior shading may require structural mounting, professional construction, wind-resistant hardware, and periodic maintenance. Fixed awnings also have to be designed carefully. A poorly sized awning might block valuable winter sunlight while failing to provide enough shade during the hottest part of the summer.

Exterior shades can provide excellent heat control, but they are generally more visible and mechanically complex than window film.

Cellular Shades

Cellular shades, sometimes called honeycomb shades, contain small air pockets that help reduce heat transfer through the window area.

They can improve comfort, particularly when they fit tightly against the window frame. They can also provide insulation during colder months, making them a useful year-round interior covering. However, cellular shades work best when they are closed. This means the homeowner must sacrifice natural light and the outdoor view whenever heat control is needed. Solar energy can also pass through the glass before reaching the shade. The shade may absorb some of that energy and become warm, leaving part of the heat inside the room.

Cellular shades are often most effective when combined with solar window film. The film reduces solar heat during the day, while the shade provides additional privacy and insulation when closed.

Blackout Curtains and Thermal Drapes

Blackout curtains are one of the simplest ways to make a room feel darker and somewhat cooler. Heavy thermal drapes can also reduce heat transfer around a window.

They are useful in bedrooms, theaters, nurseries, and other spaces where blocking light is not a problem. The major limitation is that blackout curtains control heat by covering the window completely. You lose the view and most of the daylight while the curtains are closed. Curtains also sit inside the room. Sunlight can still pass through the glass and heat the curtain material. Some of that heat is then released into the surrounding space.

They are a practical low-cost option, but they do not provide the same always-active solar control as window film.

Trees and Strategic Landscaping

Landscaping can also play a powerful role in reducing heat entering through windows. Strategically planted trees and shrubs can block or filter sunlight before it ever reaches your home.

Deciduous trees are especially effective because they provide shade during the summer while allowing sunlight through in the winter after their leaves fall. Placing trees on the south and west sides of a home can significantly reduce afternoon heat gain.

Shrubs and hedges can also help by shading lower windows and reducing reflected heat from nearby surfaces like patios or driveways.

However, landscaping is a long-term solution. Trees take time to grow, and placement must be carefully planned to avoid blocking views, interfering with structures, or causing root issues. Maintenance is also required to keep plants healthy and properly shaped. While trees and shrubs can reduce heat naturally, they are often most effective when combined with other solutions like window film for immediate and consistent results.

Blinds

Blinds are helpful for controlling brightness, privacy, and the direction of visible light. Light-colored or reflective blinds can also reduce some heat gain when fully closed. However, standard blinds are not primarily designed as solar heat-rejection products. Gaps between the slats allow light and heat to pass through, and the blind material itself can become warm. Like curtains and shades, blinds also have to be closed to provide their maximum benefit.

Blinds are valuable for privacy and light management. If the main problem is a room becoming unbearably hot, they may work better when paired with a solar control film.

Low-E Replacement Windows

Replacing older windows with high-performance low-emissivity, or low-E, windows can improve insulation and solar control.

Low-E coatings are microscopically thin layers applied to glass to manage heat transfer. Certain low-E glass systems are designed to reduce infrared heat while continuing to transmit daylight. The Department of Energy notes that spectrally selective low-E coatings can filter a significant portion of normally transmitted heat without eliminating natural light.

Replacement windows may be the right choice when the existing windows are damaged, leaking, fogged between panes, difficult to operate, or near the end of their useful life. However, replacing a complete window system solely to address solar heat can be an expensive project. When the frames and insulated glass units remain in good condition, window film may offer a more targeted way to improve solar performance.

What About DIY Reflective Film?

Home improvement stores and online retailers sell temporary reflective sheets, static-cling products, and adhesive films marketed for heat control. These products may provide some short-term improvement, but their performance, clarity, durability, and compatibility with the glass can vary significantly.

Poor-quality materials may:

• Bubble or peel
• Distort the view
• Leave adhesive residue
• Fade or discolor
• Create uneven absorption across the glass
• Provide little verified performance information

Not every film is appropriate for every type of window. Glass thickness, pane configuration, coatings, shading patterns, window orientation, and existing damage can all affect product selection. The International Window Film Association recommends evaluating factors such as the type and location of low-E coatings before applying film to low-E windows.

A professional installer should identify the glass and recommend a compatible architectural film rather than applying a generic material based only on darkness or appearance.

Which Windows Should You Treat First?

You do not always need to apply film to every window in the home.

Start with the rooms where heat creates the biggest comfort problem. These commonly include:

• West-facing rooms that become hot in the afternoon
• South-facing rooms with prolonged sun exposure
• Large living room windows
• Sliding glass doors
• High windows and skylights
• Home offices affected by glare
• Bedrooms that remain warm into the evening
• Rooms with hardwood floors, artwork, rugs, or valuable furniture

Treating the most problematic exposures first can make a noticeable difference in how the home feels.

A professional consultation can also help identify why the room is hot. Window film can address solar heat entering through glass, but it cannot repair failed seals, missing insulation, air leakage, undersized air-conditioning equipment, or poor ductwork.

What Is the Best Material to Put on Windows to Keep Heat Out?

For most homeowners who want to reduce solar heat without covering their windows, professional solar control window film is the strongest all-around option.

It works throughout the day, preserves more natural light than curtains or blackout shades, and can be added to existing windows without a complete replacement project.

Exterior shades and solar screens can be highly effective when blocking sunlight before it reaches the glass. Cellular shades and curtains can provide additional insulation and privacy. Replacement windows may be appropriate when the current windows are damaged or outdated. Natural landscaping provides privacy and filters the light.

In many homes, the best solution is a combination. Window film handles daily solar heat and glare, while blinds or shades provide adjustable privacy and nighttime coverage.

Keep Your Home Cooler Without Losing the View

You should not have to keep your curtains closed all summer just to make your home comfortable.

Optimum Window Tint installs residential solar window film throughout Utah to help homeowners reduce heat, control glare, protect interior surfaces, and enjoy more consistent comfort. We can evaluate your windows, discuss clear and tinted film options, and recommend a product based on the glass, window orientation, appearance, and performance you want.

Request a free window film quote and find out which windows are contributing the most unwanted heat to your home.

Request a Quote

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Sources

• U.S. Department of Energy – Windows and Energy Efficiency: https://www.energy.gov/energysaver/windows
• U.S. Department of Energy – Window Types and Technologies: https://www.energy.gov/energysaver/window-types-and-technologies
• National Fenestration Rating Council (NFRC): https://nfrc.org
• International Window Film Association – Heat Control: https://iwfa.com/heat-control
• International Window Film Association – Window Film FAQs: https://iwfa.com/faq
• U.S. Department of Energy – Landscaping for Energy Efficiency: https://www.energy.gov/energysaver/landscaping-energy-efficient-homes

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