Fish Window Cleaning Blog

Developed in 1934 by American refrigeration engineer Charles D. Haven, these windows became available on the market in 1946 and were known as Thermopane units. Interestingly, the Old John Hancock Building (as it’s now known) in Boston was the first major architectural project to feature Thermopane units, using 16,205 of them!

Fog, seals and other factors

There are a few aspects to consider when it comes to how to clean this type of window. First is to know if the windows are just foggy, something that may make windows appear dirty when, in fact, they are not. Next is investigating the seal. Often the seal of a double paned window is actually damaged, not dirty, and needs to be replaced. Finally, you need to know how to access the panes in order to clean them.

Are the windows just foggy?

The design of Thermopane windows makes them prone to fogging up inside. This can make them look dirty because it reduces visibility through the window. As a first step, you want to remove any condensation that has built up between the panes.

The safest way to draw out the moisture that’s trapped between the panes is to place a dehumidifier next to the foggy window. Set the dehumidifier as close to the window as possible. There are small dehumidifiers you can purchase as well that can sit right on the windowsill, or you can try making your own dehumidifier. For example, get a small container that fits on your windowsill and fill it with baking soda. The baking soda will harden as it absorbs moisture. You can also use charcoal (get a large can with a lid, put the charcoal inside and punch holes in the side of the can and the lid.)

You can also drill small holes at the top and bottom of the window where you can insert an absorbing fluid or pellet. We recommend that you get a professional to do this job because it involves breaking the seal and it could damage your windowpane. There are also concerns with glass shards if your drilling is not in the right location. With these windows, slight abrasions or cracks on the panes themselves can defeat the purpose of the insulation, as can broken seals.

Addressing the seals

Windows with two panes also have two seals — one protecting against moisture and one adding to the strength of the window. The seal holds the window spacer in place, which is an important element in the insulation factor of these windows. Depending on a variety of factors, this type of window has a 10- to 20-year life span.

Seals are important for any window, especially so when there are two panes of glass. In addition to losing efficiency with age, seals can wear if there’s too much water retention in the window frame, or if a water draining issue is present around the window. In addition, sunlight builds heat on windows, which causes panes to expand and contract, which puts pressure on the seal and weakens it over time.

A reputable window cleaning company will be able to detect if the seals are broken and if the window needs to be replaced. This can be difficult to determine on your own, but mistaking a broken seal for a dirty one can have consequences. Once the seal fails, moisture, dirt and insects can make their way into your double-pane windows, causing further damage if it goes unnoticed.

How to clean double-pane windows

To clean this type of window, you need to remove the seal and then clean each piece of glass. Take a look at how the window is framed and determine whether you’re dealing with a metal, plastic or wood sash. This will help you understand whether you can disassemble it easily or if it’s a more difficult task. For example, if the sashes are made from wood, you may need a solvent to loosen the glue so that the pane removal is easier.
 

Take your time removing the seal so as not to break the glass. After cleaning, you need to reseal the panes. Be mindful of any moisture that can be present when you’re sealing the window because that will impact the integrity of the seal. This is a difficult and precise task, but not impossible to do yourself. It’s a good idea to do this with a partner so you don't have to try to hold the glass and remove the seal at the same time.

Hiring a professional window cleaning service

With many years of experience cleaning multi-pane windows, we strongly recommend that you have a professional do this cleaning for you. The proper sealing requirements for this type of window are tricky and, if not done properly, can lead to further issues.

Many property owners consider replacing these windows with single-pane windows after this experience — sometimes because of pane breakage and sometimes because it’s just too much work to do the job effectively on your own.

FISH Window Cleaning has been offering interior and exterior window cleaning services for more than 40 years. With 270 franchises nationwide, there is likely a FISH Window Cleaning service near you. Before you give up on these windows, request a free estimate of window cleaning services. We are a licensed, insured and bonded professional service with experience in all types of windows, and it could save you some headaches in the future.