How Do Windows Fog Up in a Home?


Have you ever noticed that the windows inside your house are fogging up? The thin layer of condensation can be a little annoying because it blocks your view of the outside, but it can also be a sign that there is another issue with the humidity levels within your home, inefficient ventilation, or even the window itself.

Foggy windows typically occur more often in the cooler months of the year. The condensation occurs when the cold air coming in through the glass panels combines with the warmer air inside your home and react to create a thin layer of moisture that coats the entire window. 

What causes windows to fog up?

There are many reasons that windows can fog up in your home. If you touch the tip of your finger to the glass and discover that the condensation is on the inside of the window, chances are that the humidity levels within your home are too high. Homeowners should be careful of excess humidity in their homes because it could lead to much more serious problems like mold and mildew. 

To fix humidity levels, consider investing in a dehumidifier and see if that helps with the foggy windows. However, more often than not, the reason that the windows are fogging up in your home is because the window seals themselves are failing. This is normal and can be caused by a number of things, included excessive rain like that of a tropical storm or mere old age of the window. 

When your windows are fogging up excessively, chances are that the seals are breaking down and that you will likely either need to replace the seals or the entire window itself. Consult a professional for an expert opinion before you make any decisions on your own that could end up being more costly than necessary. 

Why are window seals important?

The majority of windows in homes are insulated windows. The way that insulated windows work to increase energy efficiency in your home is with two panes of glass with a thin layer of air between them that keeps the warmer air inside of your home rather than letting it escape. There is a seal around the insulated glass unit (IGU) to ensure that this energy efficient situation can occur.

When the seal around the IGU breaks down, whether it is because of extreme weather, high levels of heat, or old age, moisture can sneak in between the two panes of glass and create the condensation that results in foggy windows. As previously explained, this is more common in the colder months of the year when the cooler outside air mixes with the warmer inside air.

How do you fix foggy windows?

Once it has been determined that the failed seal is what is causing your insulated windows to fog up, you have a couple of options. Firstly, you can have the seal or the IGU replaced. This process is usually cheaper than replacing the entire window, but it can also be very difficult and shouldn’t be attempted by someone who isn’t familiar with windows. 

An insulated window is more complex than it looks and is composed of many different parts, so if you aren’t a professional, it’s better for the homeowner to seek out the help of one if they want to simply replace the seal or the IGU. However, in most cases it is just better to replace the entire insulated window, especially if the seal has failed because your windows are old.

While it may be more expensive to purchase new windows, it can actually be much more cost effective in the long run to replace foggy windows because it will increase the energy efficiency of your home. Thus, if you install windows with fresh seals, there is a higher likelihood that the heat will stay inside your house where it belongs and lower your energy bills. 

Do defogging sprays help windows?

Perhaps you don’t want to go to all the trouble replacing your window units or there is something else preventing you from seeking that solution. There are various defogging sprays on the market that will keep your windows clean and free from condensation using a complex mixture of chemicals. Another common, homemade solution is to apply shaving cream to the windows to prevent fogging.

However, treatments with defogging sprays and shaving cream are only temporary solutions. They will take care of the symptoms of foggy windows, but they will not fix the root of the problem. Even though defogging sprays and professional defogging treatments might be less expensive than installing new windows, it might be better to simply forego a bandaid fix and replace the windows.

Final Tips and Tricks

When the seal in your insulated window fails, it allows moisture to creep in between the two panes of glass that are designed to hold the heat inside of your home and prevent it from escaping outside into the cold. This moisture leads to condensation and the annoying foggy windows that homeowners often have to deal with in the cooler months. 

The easiest solution to this issue is to replace your windows, or at least the seal and IGU within the insulated windows. It is up to the homeowner to decide which is the right choice for them and their home, but it is undeniable that, once the seal breaks down, the only solution is to get a new one.

When purchasing new windows, always be sure to buy the most energy efficient ones so that your home can stay cozy in the cold seasons and you can cut your energy costs significantly. It’s also a good idea to buy windows with a lifetime guarantee so that you know the seal around the IGU is going to hold for a signficant amount of time.

Finally, make sure that the new windows are installed properly. If you aren’t confident replacing them yourself, don’t hesitate to hire a professional. Your home and your wallet will thank you at the end of the day.