Professional rundown of window security and window types

 Windows are the weakest point in a building envelope and are the target for entry of many intruders.

From an intruders point of view, when they look at a home or building they are naturally scanning for the weakest points of the building envelope. These are the points where they’ll try to gain entry into the home.

There are a variety of window types and they each represent a different level of challenge for an intruder to breach.

Here we’ll list the different types of windows commonly found in North American homes and discuss the design, operation and vulnerabilities of each window type. After that we’ll discuss the most effective type of high security window available.

Double Hung Window

Double hung windows

The double hung window is an American classic. As seen in the image the double hung window gets its name from the fact that in the window frame there are two sashes which are hung, thus double hung. If the top sash is fixed in place it would be called a single hung window.

Over the years the double hung window has gone through many upgrades and improvements to make it more energy efficient.

“Upon closer inspection, a double hung window is more of an aesthetic window than it is an energy efficient window.”

But style and building heritage being as it is, double hung windows are not going to be going away any time soon. 

The action of a double hung window is for the two sash to slide up and down in the frame allowing for air to flow. You can pull the upper sash down to allow the hotter air inside a room to escape while at the same time raise the lower sash to allow the inflow of cooler air.

It is an elegant design which has its originations in Europe. The principals at play in the use of the window are to take advantage of the physical properties of air, that being, hot air rises and cool air sinks.

Double Hung Window drawingModern designs of the double-hung window

strive to create as tight a weather seal around the perimeter of the sash while at the same time making the sash as easy to slide up and down as possible.

“This apparent contradiction of design objectives makes the double hung window an  engineering challenge.”

On the one hand you want the sash to slide up and down easily so it is nice to operate.

On the other hand you want that sash  to fit into the frame as tightly as possible to increase weather tightness and the ability of the window to keep wind and water out. There is almost no security considerations regarding the design of a double hung window. There is a sash lock which connects the two sash together when they are both in the closed position, but the sash lock is built into the window strictly to increase the weather tightness of the window and not as a anti-intruder security measure. 

Security Window Learning

Double Hung Security

Quite often the sash lock is never used which leaves a simple to open window for an intruder to enter. When the sashes are locked to each other it is difficult to raise the sash to gain entry, but this small obstacle can be overcome by simply prying the two sash part where they lock.

Of course there is the good old ‘place a stick’ on the upper sash which inhibits the sash from being lifted up. So let’s say you have successfully secured the sash and an intruder can’t open the window in  the usual way, then the next option is for the intruder to break the glass.Burglar entering house

One of the advantages of the double hung window is that there are two glass units (one in each sash), this makes the opening smaller and more difficult for the intruder. 

Can I convert my double hung windows to security windows?

Double Hung Window Parts
Pella drawing

Suppose you were to want to place high security glass into one or two of the sashes of the double hung window. This is highly unlikely and would almost definitely not work unless it was a very very small window.

The reason is this, as stated earlier, a double hung window is designed to be easy to lift and lower the sash, if you put high security window glass in one of the sashes then the weight of the sash becomes very problematic.

Therefore this type of design is practically never done. In conclusion regarding double hung windows it can be understood that the love of the window particularly in New England and other northern states is for the architectural style it represents and not really the energy efficiency.

Furthermore, the actual design of a double hung (or single hung) makes it almost impossible to put a high security glass unit into the sash.

So while a double hung is a beautiful window to look at and use, it does not give itself to high security requirements.

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Slider windows – Slider window security.

A slider window is almost exactly like a double hung window except that the windows slide horizontally and not vertically as in a double hung window. Slider windows are often used in where the width of the window is greater than the height, which makes them useful for basement windows. Although they are often found on all floors of a home.Slider Window Drawing

The security level of a slider window is almost exactly the same as the double hung, but with one main difference. On a slider window the sash does not need to be lifted because the action of the sash is to slide it to the left or the right. In this case the sash may be considered to be more accommodating for heavy security glass, but that is only part of the story.

The fact remains that the sash of a slider is still very easy to remove due to the fact that it only has one connection point to lock it in place and that is against the other sash. So as a security window, a slider is not a very good choice.

Casement Windows – Casement Window Security.Double casement drawing

Casement windows are a popular style of window when the design of a home is more contemporary. Casement windows have cleaner lines than a double hung window and the operate in a completely different way. Casements window are designed around the same principals of a door. The sash in these types of windows swings outward while it stays attached to the window frame on the left or right side.

The swing action is not unlike a door but the the hardware for a casement window is quite different. Casement windows have one sash which is hinged to the frame. the sash in a casement window holds the entire insulated glass unit, unlike a double hung where there are two separate glass units. There are three basic hardware components on a casement window.

1. Sash Hinge

2. Hand Crank

3. Sash Locks

 Because there is only one sash in a casement window and the hardware is different from a double hung, there are considerable energy efficiencies gained by the design. When in The closed position, the sash of a casement window is compresses around the entire perimeter in direct contact with the weatherstripping on the frame. This compressed weather tight seal is enhanced by the extra pressure exerted from the sash locks and the hinges. Laboratory measurements and testing has proven over and over the superior wind and water resistance a casement has over a double hung window. 

Intruder breaking into casement windowCasement vs Double Hung Security review

It would seem to reason that one could also anticipate that a casement window would offer a higher degree of security. Unfortunately this isn’t so, even though it is more weather proof, casement windows offer little gain in security. In fact there are some features which may make them even a bigger security weakness when compared to double hung windows. Namely, the whole window is filled with with just one glass unit.

By comparison, if there is a 30” wide x 60” high double hung window and a casement of the same size, then a comparison of the glass units will offer an insight. In the double hung there will be two glass units 30” x 30”.  This means that if the glass in the lower sash of the double hung gets smashed then the space to enter the home is 30” x 30”. Alternatively, if the glass in the casement window is smashed then the space to enter the house is 30” x 60”. So simply from a “entry hole” size comparison the casement window offers an easier passage into the home.

Double Hung Window vs Casement Window

As mentioned elsewhere in this article, it is important to note that the hardware used in common windows is very light duty hardware and is only designed to keep out the breezes of the wind and the rain falling from the sky.


So even though a casement window has a crank handle to open or close the window and there are sash locks on the frame of the window (maybe even multipoint hardware) it is not heavy duty hardware and does not represent a meaningful obstacle to an intruder. For example, it is very common for the hardware of casement windows to be attached to the frame and sash with screws which are less than 1/2” long. Pulling out a 1/2” screw from plastic or wood is a very easy feat.

Can casement windows be made more ‘burglar proof’?  

The short answer is NO. It is not possible to take a standard casement window and try to dress it up with some after market parts to make it ‘burglar proof’ this is because the overall engineering of the window is based only on weather-tightness and ease of operation. It is essential to recognize that a true security window is a combination of materials and engineering which is designed to be secure from the start. Taking one type of window and trying to magically change it into a high security window is an impossible task. The best you can do with a common window is to add some type of after market enhancement in the  hope it SLOWS DOWN the intruder. 

To further the point, impact resistant glass which is required for a true ‘burglar proof’ product is much too heavy for regular casement hardware. Especially because the action of a casement window is to swing out from the house, where it will also be exposed to the additional stresses of wind and heat. As it stands right now, most window manufacturers will not create a casement window wider than 36” simply because regular glass is just too heavy, not to mention high security glass which is magnitudes heavier.

Awning Windows – Awning Window Security

Awning Window
Milgard window

Awning windows are similar to casement windows in many ways therefor many of the same arguments made above regarding casement windows are the same for awning windows. The main difference between  casement and awning windows are similar to the comparison of double hung and sliders.

That is, awnings use similar hardware to a casement but in a different orientation. Awning windows have the sash connected to the frame by hinges on the top of the window, so the sash swings out from the frame much  like the cover over a mail slot.

Similar to the casement window, awnings only use the most light duty of hardware because the requirement of the hardware is to keep out wind and rain, it is not designed to keep out thieves or intruders. For the same reasons as the casement and double hung, after market treatments do not have the ability to convert a common awning into a security awing, it simply doesn’t work like that.

Fixed windows (Non-operator) – Fixed Window Security.

In a fixed window there is no sash and no operating hardware. it is simply a glass unit mounted into a frame. It could be imagined that for a fixed window it would be possible to place security glass into it. But this concept should be considered from an engineering point of view and looked at rationally.

Frame construction of common (or typical) windows is a mass production, lowest price wins, state of affairs. This means that the only level of certainty you have when buying a typical window is that it will keep out most wind and rain. There is never security built into common frames, and it would be dangerous to think so.

So it is impossible to take a regular window frame and put high security glass and to be able to reasonably call the window a “security window”.

At best it should be called “a security glass unit inside a common window frame”.Burglar coming in window

In the aftermath of a break-in and robbery to someones home, there is always a very detailed investigation into what the exact weakness was that the intruder exploited. The purpose of this article is to elucidate upon the different characteristics of window construction and to breakdown the possible weak-points of common window designs. More importantly, this article is designed to give you the education before hand of what you need to think about regarding window security. 

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