Failing Window Seals


One cold morning after waking up, you notice some condensation on your double glazed window or patio door. Wiping away doesn’t help and the moisture stubbornly remains in view. Unfortunately this time the condensation sits between the two glazes of glass and this typically occurs when the seals on your windows are damaged or broken.
Halloween just behind us, what can be scarier than broken window seals, that let cold and damp in?

What are Window Seals?

Window seals Double glazed windows and patio doors are manufactured to have a factory seal around the perimeter. This seal is designed to hold the sheets of glass apart and acts as a frame holding the structure together. The gas between the glazes of the window which is actually a thermal break separating the inside and outside temperatures. This includes many benefits such as the ones we explored in a previous blog post ‘8 Ways Double Glazing Enhances Your Home’ Adding of different gases (like argon and krypton), films and coatings between the glazing increases the insulating properties of the window.

Why do Window Seal’s Break?

There are number of reasons why window seals can deteriorate and brake. Effective working window seals are an absolute necessity for proper insulation to avoid heat escaping from your home. That is why it is important to prevent seal damages. We have collected the common causes for window seal damages:

• Water
Condensation and moisture resulted damages are the most common cause for window seal deterioration. When the window is exposed to condensation for a long period of time it deteriorates window seals. For example when the window sits in the water it slowly seeps in and damages the seals.

• Mould
Rubber seals are particularly sensitive to mould damages. Regular condensation on your windows makes them exposed to mould growth. This can be detected easily as it causes discoloration on the seals. Moulds reproduce by means of tiny spores which can be effectively killed by alcohol based cleaning products, or vinegar if you prefer green cleaning methods.

• Temperature & Climate
Significant fluctuation in the outside temperature can cause damage because hot air softens perimeter seals and glazes can bow outward.
Another problem is that in the UK humidity levels and wet winter makes condensation inevitable. In this climate perimeter seals tend to dry out, crack and allow moist outside air to infiltrate.

• Strong cleaning products
Using harsh cleaning products such as bleach might also eat away at the seal, it is smart to choose milder cleaning products for our windows.

• Faulty installation
Other reasons for your double-glazing unit failing include faulty installations or faulty production methods which is why it’s paramount to consider the quality of your windows when purchasing them.
The best defence against failure is prevention. It is wise to examine windows, frames and seals couple of times a year. At Crystal Clear all of our windows are “A-Star” rated and come complete with a 10 year piece of mind guarantee.
You can also protect your double glazed windows by ensuring good air circulation to avoid excess moisture. Keeping the window seals clean and well-sealed with paint makes preventing future damage easier. There are more companies offering weather resistant paint systems (primer, undercoat and gloss) such as the Dulux Weathershield System.

3 Tips on How to Treat Broken Window Seals

1. Check your warranty

The most reputable double glazing suppliers offer 10 years of guarantee which means if the seals are failing on your windows or doors they will be replaced for you. Premature seal failure will often be a sign of a defective product. Glass manufacturers tend to include their name or ID, as well as a manufacturing date or date code, near the spacer or bottom of the glass so you can determine whether a failed glass unit is still under warranty.
If you are looking at getting your double glazing replaced, ensure any guarantees are insurance backed.

2. Replace the window

Because of the high humidity climate in the UK, broken window seals often result high condensation and moulding. This can ruin the aesthetic of the window and diminishes the view. Having new and quality double glazed windows professionally installed is a good investment to prevent future seal failure.

3. Replace the seal

If you like DIY jobs, replacing your own window seals could be the solution for you. The work is bit time consuming but absolutely doable. You’ll need the following tools for the job: a replacement gasket, a slender flat knife, needle noosed pliers and a sharp pair of scissors. There is quite a selection of replacement gaskets on the market. If you are not sure which one to choose, pick a universal one.

1. Prise out the existing seal and remove it along its full length. Use your scissors or the needle noosed pliers for the removal.

2. Clean the window edges with some window cleaner. Ensure it is cleaned properly.

3. Measure your new seal along the width of the old one, which you have just removed.
For movement allow an additional 15 mm.

4. Cut off a section at one end and cut the end at 45 ° working inwards. Avoid overlaps to make sure no water can penetrate into the frame. Use your thumb to push the seal into place. It should clip into place with no creases or gaps.

5. Cut off the excess on the opposite edge and push the gasket into place. Mark the gasket seal on the point it reaches the corner and cut it off on the mark. As earlier, cut off a section at one end and cut the end at 45 ° working inwards. Ensure the seal is in the correct position.

6. Follow the same procedure for replacing the remaining seals.

Need a hand?

At Crystal Clear, all of our windows are “A-rated” and come with a 10 year peace of mind guarantee to cover you and your home. Looking to replace or upgrade your window? The team would love to hear from you! Give us a call on 0117 911 0272, or just pop into our showroom to meet with our experts face to face and see examples of our range up close.