Types of Window Glass

It's surprising how many different options there are for types of window glass.

There are plenty of aspects to consider when selecting your window glass (not necessarily in this order).

• Optical clarity / privacy
• Energy performance
  
• Safety
• Security
• Aesthetics

And the glass needs to work alongside the other parts of a window.

The priorities differ for different spaces in your home so it's important to consider each window in turn.  You may well need several different types for different windows in your home.

For example you will need privacy in the bathrooms and perhaps your stairwell, downstairs windows need to be more secure than upstairs windows and perhaps you want to make a decorative statement with one of the windows that faces the street.

It's often possible to mix and match different characteristics in one window (more on this at the bottom of this page).

The following types of window glass feature on this page...

Standard float glass

Float glass is the glass that's used as the base for all other types of window glass.  It's the lowest cost but has no features in terms of security, safety, energy, privacy or color.

It breaks pretty easily into dangerous shards and has poor energy characteristics when used as a single pane so it's well worth considering other types of glass for your home.

Standard float glass characteristics

Toughened glass / tempered glass

Toughened or tempered glass is stronger than ordinary types of window glass which makes it harder to break and therefore safer.  The main safety feature of tempered glass is that when it breaks it shatters into lots of small pieces which won't give you large lacerations if you're unlucky enough to be in the way.

It's a good idea to get all your skylights made of the toughened or tempered type of window glass, if not laminated glass.

If your window is less than about 1 ft 6 ins (45 cm) most building codes require tempered glass for safety.

For those interested in the chemistry, toughened (or tempered) glass is created by carrying out an annealing process on standard glass.

Toughened / tempered glass characteristics

Laminated glass

Laminated glass is very safe and it's the best type of window glass when it comes to security because it's really hard to break through it.  It's made of two thin sheets of glass glued together by a plastic layer that is flexible.

It takes a lot of time to break in through a laminated glass window.  Once it breaks, the pieces are held in place by the plastic layer.  Any intruder then has to break the glass then somehow get through the laminated layer.  Not a quick task as you can see in the video below (after the characteristics table).

This is a great video that demonstrates how differently standard, toughened (or tempered) glass and laminated glass behave when they are broken.

Laminated glass characteristics

Plastic glass

This section refers to acrylic, plexiglass / perspex and there are other brand names out there for this type of window glass (sorry, plastic).  Plastic glass is safe because once broken, any shards aren't as harmful as glass.

Modern plastic glass is optically clear, has good insulating properties and it's up to 10x more resistant to breaking than glass.  It's used in some skylights and can be used to retrofit secondary glazing.

Plastic glass characteristics

Patterned glass

Patterned or obscured glass is created by giving one side of the glass a shape that distorts the direction of the light rays while still letting all the light through.  This type of window glass is described as translucent.

The quality of light through translucent glass gives a wonderful glow with only ephemeral hints of what is going on behind the window, hence the privacy.

Here's a few examples of patterned types of window glass.

Patterned glass characteristics

Etched glass

Etched glass is where the surface of the glass remains flat but it is etched or ground to give it a cloudy appearance.

The whole pane can be etched and some window suppliers offer patterns if you want to make a bit more of a design statement.

The pictures below show a few possibilities for etched types of window glass.  Essentially any design is possible.  To maintain privacy make sure that the majority of the glass remains cloudy.

Another idea is to leave a small amount of clear glass around the edge of the pane.

Or get half of your pane etched to provide privacy where required, but let maximum light through where possible.

Etched glass characteristics

Mirrored glass

Mirrored glass may not seem an obvious choice for your home.  We're more used to seeing it in the interview rooms on our favorite crime dramas or on sky scrapers.

Mirrored glass is great if you need privacy and still want to be able to see the outside clearly.  However, there will be a slight degree of light loss because mirrored glass tends to have a slight tint to it.

Mirrored glass also helps to keep the internal temperature down as it will reflect a certain amount of the sunlight.

Remember that with this type of window glass you'll still need curtains or some other window treatment because at night when light levels inside are greater than the outside, the mirror effect is lost.

Your window supplier may have different colors of mirror glass available.

Mirrored glass can be used as a real feature if it's used on the whole home.

Here are two of my favorite mirror houses....

Mirrored glass characteristics

Fire resistant glass

Fire resistant glass is only required in residential settings when a larger than usual proportion of the the external walls is constructed with glass.  If you imagine a room with a high ceiling height with glass walls on two sides - then fire resistant glass might be required.

Fire resistant glass means that the glass will stay intact in case of fire for longer than normal glass and will also keep the temperature on the other side of the glass lower than normal glass.

Fire resistant glass characteristics

Wire glass

You usually see wire glass in large buildings such as schools and hospitals.  It can be useful in a residential setting when you want fire resistance and the appearance isn't important.  I have seen it used in sheds and other outdoor utility buildings.

The wire makes it safer and somewhat more secure in terms of fire resistance and ease of breaking.

It's available in both clear and patterned glass.

Wire glass characteristics

Low emissivity and solar control glass

Low emissivity (or low-E) glass controls solar gain by reducing the transmission of infrared radiation (heat) while still allowing most of the light to pass through.  It also works in reverse, so in winter the heat is kept inside your home.

Consider specifying low emissivity glass in large areas of glazing in the following areas:

• Conservatories (a room with glass walls and glass roof).
• Large areas of glass that face the sun.  This depends on the hemisphere you're living in (south facing for northern hemisphere, north facing for southern hemisphere).  Read more about orientation towards the sun.
  

This type of window glass is often tinted to be sure to see a good sized sample before you order.  Also, I've heard that it may cause disruption in cell phone reception.  Check with your window supplier.

Low emissivity glass characteristics

Colored and tinted glass

Colored or tinted glass can be used for a whole pane but is more commonly used in stained glass windows.  Stained glass windows add to the aesthetic of your home and are also another option to add privacy.  Stained glass panels can sometimes be installed as an internal window.

Some window suppliers have off the shelf stained glass designs you can choose from.  If you want to have a design made be sure to ask your window supplier how this might be possible.

Colored glass characteristics

Self-cleaning glass

Self cleaning glass - sounds like science fiction but it's really truly available!!  A coating of titanium dioxide is applied to the glass.  Self cleaning glass has a blue tinge to it so it works best when the whole area receives direct sunlight.

Balconies are an ideal setting to use self-cleaning glass.

I found this great article on self-cleaning windows which is well worth a read if you're considering self cleaning for one of the types of window glass for your home.

Self-cleaning glass characteristics

Electric Glass / Switchable smart glass

Electric glass or switchable smart glass refers to panes of glass that can change properties at the touch of a button, or on movement sensors.

It can be used in both internal and external applications.  There are a few different types available:

• Privacy glass where the glass changes from clear to translucent.
• Solar glass where the solar control qualities (the low-emissivity) qualities can be turned on and off.  The glass always appears clear.
  
• Blackout glass where the glass changes from clear to totally opaque.
  

Noise reduction glass

There is no special glass as such that reduces noise.  Noise reduction in windows is achieved by using double or triple glazing (see below).  The gas filled space in between each pane of glass acts as a sound break.

Double and triple glazing

Double and triple glazing refers to using two or three panes of glass respectively in the same window area rather than a special type of window glass.

The area between the two (or three) panes of glass is sealed and the air replaced with gas (usually argon).  The argon gas creates a heat and sound break.  The spacer contains a desiccant which prevents any moisture build up.

For more on the performance of windows take a look at the window efficiency page.

Secondary glazing

If you aren't planning to replace your single glazed windows then secondary glazing may be an option for you.  This is where an extra pane of glass (basically a second window) is installed on the inside of the existing window.

Secondary glazing is much more affordable than double glazing and it can be a DIY job.

Double / triple glazing characteristics

Glass block

Last but not least of the types of window glass is glass block.  I've left it until last because it's more of a glass wall than a window.

Glass blocks are made by fusing together two halves to create a vacuum inside so they're effectively double glazed.  This gives glass block the insulation qualities equivalent to a double glazed window.  They're also hard to break which makes them secure and safe.  Of course a glass block wall does not open so it can't be used as a fire escape route.

They come in a number of finishes including totally clear.  Similar to normal glass, the patterned versions provide privacy and still let the light through.  They're suitable for both internal and external use.

Glass blocks are assembled like a wall and the mortar lines create louvers which create shade in the summer when the sun is high and let the light through when the sun is low in the winter.

If you're thinking about using glass block, some suppliers supply the wall already mortared together.

Glass block characteristics

Window films

For nearly every type of glass there is a window film that does the same job.  For example:

1. Obscuring window film
2. Mirror window film
3. Safety window film
4. Colored glass film
   
5. UV / solar window film

This is really useful if you're remodeling and you don't necessarily want to replace your windows.

Indoor decorative glass

Fabric glass

Fabric glass is where a piece of fabric (usually see through fabric) is sandwiched between two layers of glass.

This type of window glass is used more in indoor window and glass applications that for windows to the outside.

Painted glass / verre eglomise

Put simply painted glass or verre eglomise this is where a design is painted onto the glass.

You could use a plain color as a backsplash or a more elaborate design.

I hope you've found this page on types of window glass useful.  Now take a look at the other pages on window design.

More window design