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What Are Glass Block Windows?

Discover all the multiple benefits that glass block windows can bring to your home in terms of aesthetics, safety, privacy, and energy efficiency.

This is a close look at glass block windows.

When you break it down to its simplest terms, windows are really just holes in the wall. At least, this is how the very first windows started. From this simple design, windows evolved into all sorts of different styles. They’re made in single-pane, double-pane, single-hung, double-hung designs and a whole huge range of different looks.

But glass block windows are a little bit different than almost all other types of windows. Glass block windows can be used for the exterior or the interior of the home. They can be put anywhere. And if you don’t want to, you don’t have to cover them with a window treatment. There’s a lot more to learn about this unique-looking window style.

Related: Egress Windows | Casement Windows | Storm Windows | Soundproof Windows | Types of Windows

What Are Glass Block Windows?

Glass block windows are so named because that’s exactly what they are: windows made up of thick, glass blocks. You’ll most commonly find them in basements and bathrooms, though they can be installed anywhere. Glass block windows can be used for exterior or interior walls.

Unlike standard windows, which are made with panes of glass, these windows are a bit like a masonry project. Glass block windows are extremely secure because they’re so hard to break. On average, glass block windows are two to three inches thick.

These windows are ideal for bathrooms because glass block windows still allow light to enter the space but they don’t compromise privacy at all. You can’t really see through glass block windows, at least not clearly.

This is a close look at the interior of a glass block window adorned with a potted plant.

The classic design of glass block windows is small, symmetrical glass blocks cut into squares. This was the design that was highly popular in the 1950s when glass block windows became a trendy design choice. Modern glass block windows are made in a huge variety of designs that use glass blocks in many different sizes and arrangements. Glass blocks may no longer even be squares. Now, these windows are styled with blocks in all kinds of different shapes and may even be curved.

It makes sense that glass block windows are popular for bathrooms, where you need your privacy. But why are these windows also used so often in basements? Because of how thick they are, glass block windows are highly insulating. This is especially useful in basements, which are often cooler than the rest of the house in winter.

Because these windows also provide security, they’re a great choice for basement windows. Standard basement windows are a weak point for homes because these windows are usually not noticed as easily and not protected as well as other windows in the home.

Due to the way they’re designed, glass block windows provide a prism-like effect. When light shines on them, it is reflected and refracted. This provides added illumination to brighten up any space.

When Were Glass Block Windows Invented?

Glass blocks started to widely come into use in the 1900s. They’ve been used in both residential ad commercial buildings of all kinds. The look really soared to popularity during the Great Depression of the 1930s, because glass is such an affordable material. Glass block window designs became popular again in the 1950s and in the 1980s, though these never totally faded from style since they came into popular use in the early 1900s.

How to Install Glass Block Windows

This is an exterior look at a glass block window above a red brick wall.

Glass block windows don’t look like other types of windows and they aren’t installed like other types of windows, either. There are several different methods that can be used to install glass block windows.

The easiest and most affordable method of installing glass block windows is to simply stack them together inside the window opening. However, there are more solid installation options. Because these windows are literally made up of glass blocks, they can also be installed like standard bricks. That means they are laid out course by course, with a layer of mortar and sand between each row of bricks. This is a very durable, strong design.

The most expensive installation option is glass block windows constructed with vinyl spacers between them. The design is expensive but it’s also more energy-efficient and more waterproof than both other two construction methods.

You can install glass block windows on your own if you have the right materials and the time. However, if you haven’t got any experience with masonry you may find this project rather daunting.

Living With glass Block Windows

This is a look at a simple dining room with a wooden dining set adorned by a large glass block window.

They can create a unique look, they’re extremely secure and they’re energy-efficient. So what’s wrong with glass block windows? One thing that you may want to consider is that these windows can’t be opened in any way. Glass block windows, by design, do not allow for ventilation. These are fixed windows. However, some designs do include a small vent with a hinge that can be opened. This is especially common in glass block windows that are installed in bathrooms.

Glass block windows add a distinct look to any space and immediately stand out. However, this style is heavily associated with older building styles. Glass block windows can look a little dated, so you want to choose the style of your windows carefully. Glass block windows are expensive to install initially, but they can pay off in energy savings and they add a lot of beauty to any space. Now that you know about this style, you know whether or not you should add glass block windows to your home design.


What do you want to know about glass block windows?

There are several questions about these windows that homeowners have the most often.

Are glass block windows hurricane-proof?

Standard glass block windows are not necessarily hurricane- or tornado-proof. However, special hurricane-proof glass block windows can be installed. These windows are constructed precisely for strength to resist high winds.

Are glass block windows soundproof?

When installed in the usual ways, glass block windows are not soundproof. The thick glass blocks do reduce noise. However, it takes more than thickness to soundproof windows. When windows are soundproofed, they are made not only with multiple layers of glass but also with a layer of plastic that absorbs vibrations to block noise.

Are glass block windows impact-resistant?

Because they’re very strong and solid, glass blocks are tough against damage. However, they’re not necessarily completely impact-resistant. If hit with enough force, even tough glass blocks can crack.

Are glass block windows waterproof?

When installed with spacers, glass block windows are waterproof and will stay that way unless the spacers between the bricks deteriorate or become damaged. Glass block windows installed with mortar are extremely resistant to moisture, but the mortar is still subject to crumbling and chipping over time that can allow moisture to seep through.

Are glass block windows energy-efficient?

Because of the thickness of the glass blocks and because these windows are designed to be fixed in place, glass block windows are extremely energy-efficient. It’s one of the main reasons why people choose this design over other types of windows.

What Do Glass Block Windows Cost?

Glass block windows are not one of the most affordable window options you can choose. There’s a lot going on with these windows. Many windows are installed as a whole unit. This is not the case with glass block windows, which are installed brick-by-brick. You will pay, on average, $150 to $200 per brick for these windows. That is a big expense. However, you will get returns back for this investment in the form of lower energy costs.