Have you ever seen a window that looked like this? Maybe you’ve had one yourself. Chances are if you have seen or experienced one of these, your first thought was “I’ve got to get a new window because this one is so ugly.”
Regrettably, the issue is much worse than that, and may indicate that you need to consider replacing all of your windows.
This fogged look indicates that the window seal has failed and that the window has lost any efficiency benefits that it originally had.
Unfortunately, to get to this point, this window began its descent into total failure as long as a year ago, and it also probably indicates that other similar windows may have already begun to follow suit.
Today’s excursion into the eight areas of concentration as you are researching new vinyl replacement windows for your home deals with a part of thermal windows that is rarely discussed with homeowners.
Window Spacer Systems
The window spacer system is what we are talking about, and there’s a reason that it doesn’t get discussed a lot...the exchange can get kind of into the weeds. But, as you can tell from where we started in this conversation, it’s an important one.
Most windows perform well when they are first installed, but this has to do with performance even as soon as a couple of years down the road.
On the surface, a window spacer system performs a basic function. It holds the two (or three) panes together and seals them so that the argon or krypton gas stays inside.
But to insure long lasting replacement window performance, the best spacer systems need to do these three things very well:
- Minimize the transfer of heat and cold between the panes of glass
- Provide structural integrity for the glass unit
- Insure a long lasting seal
What Causes Seal Failure in Windows
Let’s unpack each of these areas. But before we do, first things first, let’s figure out what actually causes the “seal failure” that leads to that ugly, inefficient window.
In its simplest form, seal failure is caused by glass movement. The easiest analogy to illustrate this is for you to imagine a table with a razor sharp edge. Now imagine a rope laying against that sharp edge. As long as the rope doesn’t move nothing happens to it, but the minute the rope starts to move and the more (and faster) that it moves...well, you get the picture (you know the picture at the beginning—the ugly window).
Understand...glass (the rope) is always moving, you can’t make it stop.
How Do Window Spacer Systems Work
That’s where the window spacer system really comes in. What a great spacer system does is recognize that while glass will always move, the effects of that movement on the long term performance of that window can be mitigated.
So, now lets’ go back and take a look at each of those three parts of an exceptional window spacer system.
Spacer systems minimize heat and cold transfer via a process called conduction. Conduction is mainly about how heat and cold transfer through materials.
This is so important because changes in temperature are a major driver in how much glass moves.
Different Types of Spacer Systems
So, when assessing spacer systems for windows, one of the things to think about is the material that the spacer is made of as certain materials conduct heat and cold at a higher level than others. There are typically four main types of materials used in spacer systems.
- Tin-plated steel
- Stainless Steel
- Non-metallic materials (foam, rubberized, vinyl, etc.)
The aluminum and tin-plated steel spacers conduct (let heat and cold pass through) at a higher rate than their stainless steel and non-metallic counterparts.
This should make some sense, especially if you’ve ever had aluminum framed windows. In the winter if you touch the frames while inside your home, they’ll be just about as cold as the temperature is outside your home. Not good, as higher conduction rates lead to more glass movement.
Testing window spacer systems for this is called “warm edge testing.” Non-metallic spacers perform just slightly better on this test than stainless steel, but the difference is negligible.
Great Spacer Systems Provide Great Structure
Providing structural integrity is of utmost importance when it comes to exceptional spacer system performance. If the intention is to reduce the effect that glass movement has on the seal of the spacer, the glass movement must also be controlled.
This is an area where metallic spacers excel compared to the non-metallic ones, especially the foam and rubberized ones, due to the fact that they are more malleable which can allow for excess glass movement.
Within the metallic group, however, one of the things to make sure and notice is the corners. Some aluminum spacers have plastic corner keys that can expand and contract, while the tin-plated steel spacer systems typically have mitered corners that can also allow for additional glass movement.
Stainless steel spacers offer continuous corners. Between the structural integrity inherent in stainless steel and the minimal movement afforded by the corners, the stainless steel spacer system is the right choice.
How the Best Spacer Systems Protect the Seal
The last quality of superior window spacer systems has the most overall effect on the performance longevity of the glass unit. As mentioned, glass movement can’t be stopped. You can control the effects of this movement based on how long the seal lasts.
Other than lower conductivity rates, and structural protections, there are a couple of other things that premium spacer systems for windows incorporate.
- Secondary seals—All window spacer systems are sealed to the glass using some sort of polyisobutyl seal (called “butyl” within the industry). In this picture you'll see that as the dark gray. The best systems offer a secondary seal, the light gray. Often this is silicone based as the desire is not only to take advantage of the “two seals are better than one” idea, but the flexible base of a silicone sealant cushions that movement of the glass at the edges of the spacer system.
- Edge deletion—As low e glass systems have evolved, silver has become a common component. Silver has a tendency, especially in humid environments, to expand putting a great deal of pressure on the seal. While very few glass system manufacturers do this, the very best literally scrape the low e off on the edge of the glass that comes into contact with the butyl seal. This process obviously adds cost, but can add 10 to 20 times more than the standard life expectancy for the sealed glass unit.
We believe that the spacer system (as the name implies), is a truly interdependent system. For performance that’s guaranteed to last a lifetime, we believe that if the unit doesn’t excel at all three areas, the whole entity falls apart. This is why we use the stainless steel window spacer system.