Home Improvement Exterior Remodel Doors & Windows

Glass Block Windows: Cost, Benefits, Disadvantages, and More

Is Glass Block Right for Your Home?

Modern bathroom with large, open shower, jet tub
chandlerphoto / Getty Images

Glass block windows have long been used in homes as a way to bring natural light and a feeling of openness to rooms yet maintain privacy by preventing others from seeing clearly into your home. If you want privacy with art deco-style, you can do no better than by creating a curved glass block window on the front of your home, glass block in your foyer, or a glass block privacy screen in the bath.

What Are Glass Block Windows?

Glass block windows are thick blocks of glass, between 2 and 4 inches thick, that are inset into a window frame. The multiple blocks of windows are constructed like a brick wall using mortar, which is then sealed with silicone caulk. Because of the way they are constructed, glass block windows tend to be very solid and waterproof.

Tip

Prefabricated acrylic "glass" block windows that look like true glass block windows offer another option. They are lightweight and some models are operational. However, acrylic glass block can still chip, crack, and otherwise become damaged.

Is Glass Block Expensive?

The average range of installing a glass block window runs from $466 to $977. However, a very large window or wall of glass block can cost as much as $5,000 to install. Installing a prefabricated glass block window can cost as much as installing a regular window of the same size. If the glass block window is built on-site, there will be additional labor, time, and cost.

The type and color of the glass blocks will impact the cost of installation. Here's the breakdown of the average cost per block (blocks come in packs):

  • Glass: $10
  • Colored: $20
  • Acrylic: $500 (prefabricated, does not come as a single block)

Where to Use Glass Blocks

Benefits of Glass Block

Glass block is used in place of conventional clear glass exterior windows at the front of the house or on bathroom windows. It is also used as an interior non-load-bearing wall alongside foyers or in bathrooms.

Privacy is the top reason this material is installed. While lounging in the bathtub, you can get a reasonable amount of natural light filtering through an exterior glass block window, but no one can clearly see inside. Even someone who looks right up to the glass will only see vague images inside.

You can also use it for an interior screen, such as in a bathroom to shield the toilet area from the rest of the space while letting in more light than a conventional interior wall. 

Disadvantages of Glass Block

Glass block looks as substantial as brick, but it does not have load-bearing capabilities. It cannot carry loads other than its own load.

Homeowners may lose sight of this because glass block is installed much like brick with mortar. But you need to think of glass block just as you would a window: a fully self-supporting opening with fragile glass inside.

For exterior walls, you will find that glass block is so heavy that it requires a sturdy base with a properly built sill and cripple studs running vertically below it.

True glass block windows can have small vents built into them, but it's impossible to open up the entire window.

Maintenance and Durability

Glass block windows will last up to 30 years with very little maintenance. Washing them as you do other windows is sufficient. Use a power wash on the outside for an extra cleaning.

You may need to repair any chipped glass block mortar to keep the window stable. Resealing mortar with silicone caulk should be done every couple of years to keep the window in great shape.

Glass Block Window Trends

Glass block windows have come in and out of fashion throughout the 20th and 21st centuries.

Through glass blocks were developed in France in the 1930s, the best-known trend for glass blocks was in the 1940s. Film noir movies popularized the look of glass blocks. Areas that saw a lot of new, designer-driven building during the 1940s received glass blocks.

Much of the South Beach area in Miami, Florida was built up in the 1940s and this naturally included glass block windows and walls used as architectural features in homes and other structures. The glass block look was revived in the 1980s and 1990s, not just in Florida but in Los Angeles.

Glass blocks, also known as glass bricks, resurfaced around 2018 and 2019. New styles were developed, and not all glass brick had the traditional wavy-glass look anymore.

Glass Block Installation

A regular window can often be replaced with a glass block window. Instead of building glass block windows and screens from scratch, pre-fabricated kits make the job easier. Installing glass block in your bathroom or even exterior can be a frustrating project because the material is so heavy and requires a precise opening (glass block cannot be cut).

But prefabricated glass block window units operate just like any other kind of replacement window. They have the glass blocks already installed in the unit, and the units have nailing flanges on the perimeter. These prefabricated glass block window units are then installed just like any other type of window.

If you are installing your own glass block, do not use regular brick mortar. You will need to use a premixed glass block mortar and seal it with silicone caulk.

Regular brick mortar cannot be used because it has high water content, and this water gets pulled away by capillary action by the porous brick. Glass is not porous and so will not pull the water away. Glass block mortar is drier than brick mortar.

Glass Block Tips

  • Glass block isn't always used for privacy. You can purchase clear glass blocks, such as the Clarity line from Seves Glass Block, which is nearly as transparent as window glass.
  • Because glass block is hollow inside, it does have some insulating properties, much like window glass IGUs (insulated glass units).
  • Glass block windows are a security feature when used for exteriors. Glass block is very difficult to break through.
FAQ
  • Can you see through glass block at night?

    You can see hazy, unclear shapes, shadows, and figures through glass block at night.

  • Are glass block windows more energy efficient?

    Thick glass block windows offer about as much insulation and thermal protection as double-pane windows and they are more energy-efficient than single-pane windows. You can find factory-built glass or acrylic block windows that are eligible for the Energy Star label, but many glass block windows are built on-site, which means they cannot have an Energy Star label.

  • Why does glass block break?

    Glass block windows are much harder to break through than regular windows. But even though glass block is thick, the blocks can break, chip, or otherwise become damaged for a few reasons. There is no room for expansion in a glass block window, which could cause cracks or other damage. Also, glass, regardless of thickness, is fragile and can be chipped. The window itself is extremely heavy, which could cause the glass to shatter.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. How Much Does It Cost To Install Glass Block in 2022? HomeAdvisor.

  2. Clarity. Seves Glass Block.

  3. Are There ENERGY STAR Glass Block Windows? Energy Star.