The first two questions we are usually asked about double glazing are, “how much money will it save” and, “can double glazing reduce noise?” The answers are, “more than you think” and, “yes, absolutely!” it really is a wonderful invention. But why is double glazing so good?

Double glazing doors and windows have made our homes warmer, quieter, more energy efficient, and have even given us a welcome added layer of security! Here at KLG we offer a huge range of double glazing units to meet individual requirements for trade and retail customers. Not convinced yet? Let us tell you more about this game changing invention.

How Are Double Glazed Windows Made?

Double glazed windows are made by taking two panes of glass separated by a spacer bar and sealing them together into a single unit. The gap between the panes is filled with a gas before the unit is hermetically sealed (which means the gas cannot escape and no air can get in). The gas used varies, sometimes it’s just dehydrated air, but the most commonly used gas today is Argon.

Filling the cavity between the panes of a double glazed unit with dehydrated air or gas has the effect of reducing thermal and acoustic conductivity. This is because in this state, the molecules of the air or gas are much less mobile and so much poorer at transmitting sound or heat.

Here are some key facts about the history and construction of the double glazing unit:

• Who invented double glazing? We don’t know exactly who invented double glazing, but it is thought to have originated in Victorian Scotland by chilly innovators attempting to combat the harsh winters. We do know that the idea found its way to the USA in the 1930’s when the ‘Thermopane’ was developed by an inventor called Haven. It wasn’t until the 1970’s that double glazing as we know it today became popular in the UK.
• Why are double glazed windows filled with argon? Double glazed windows are often filled with Argon because it has 34% lower thermal conductivity than air, making it much more efficient. Other gasses are even better than Argon, but they cost a lot more so aren’t often used. The cost of double glazed windows filled with Argon is only about 5% more than those filled with dehydrated air.
• Is there a vacuum in double glazing? There is not a vacuum in double glazing. Technically speaking, a vacuum is the complete absence of matter and as gas is a matter, the gap between the panes of a double glazed unit is not a vacuum. However, the cavity is filled under vacuum conditions and the resulting space is often vacuum-like (meaning it is sealed at a lower pressure).
• What is the standard thickness of double glazing? The standard thickness of double glazing varies somewhat according to whether the unit is designed for thermal insulation or acoustic insulation, but generally the cavity width for standard double glazing windows is around 16mm.

How Much Money Can You Save With Double Glazing?

The money saving effect of double glazed windows primarily comes from how effective they are at conserving heat, and this depends on what we call the U Factor (sometimes referred to as U Value). The U Factor measures the speed with which a window transfers heat, and therefore how well it insulates.

• What is a good U Factor for a window? A low U Factor indicates a low rate of heat transfer and therefore a window that insulates well; glass with a U Factor of around 1.2 is a good rating for a window.

  To make things a little simpler, in the UK the efficiency of double glazed windows is rated A – G (A being the most efficient) and this rating takes into account the U Factor of the glass as well as other elements of the window’s construction such as types of frame (wooden frames are good insulators while uPVC frames have a longer lifespan).

• What is the average cost of double glazing a house? Well in order to work that out, we need to factor in the cost of actually installing double glazing in the first place. The cost of double glazing will depend on the quality of the product you purchase, but the average cost of double glazing a house in the UK is between £3000 – £5000.
• How much money will double glazing save? Again, it depends on the quality of the double glazing, but an A rated installation in a semi-detached house will save you around £120 a year. This means a £3000 installation would pay for itself in 25 years. However, it’s also important to factor in other long term savings and gains. For example double glazing will help to protect against future energy price hikes, will make your home more secure, and will add value to your property that you can recoup when you sell.
• Is it worth putting in double glazing? We think the financial argument alone makes the case; it’s a good investment that will likely pay for itself whether you stay put or sell up, and it’ll give you a much better standard of living in the meantime. This, plus the environmental benefits of double glazing, make it a no-brainer as far as we’re concerned!

How Long Does Double Glazing Last?

Generally, we reap the benefits of double glazing, such as saving money, better insulation and lower environmental impact over the long term. This is usually fine because double glazing units, particularly those with uPVC frames, have a long life span, and a good double glazed window should last around 25 years.

However, they aren’t indestructible and it is possible for them to fail. Whether you need to replace the entire unit though, or simply repair an element, depends on the extent of the failure. Here are some of the more common failure points to watch out for, along with some of the repairs to double glazing you can make:

• What causes condensation in between double glazing? When water vapour hits a cold surface, condensation occurs. If you’re seeing condensation on the inside pane of your double glazing, the temperature of the glass is too low for the room. You could switch to a more thermally efficient window to raise the temperature of the inside pane, but the problem will most likely be solved by simply improving the ventilation around your home, or using a dehumidifier. Condensation in between double glazing is caused by warm air getting into the cavity, which means your seal is no longer airtight. This is a problem because double glazed sealed units cannot be repaired, so you will require a double glazing unit replacement.
• Can double glazed sealed units be repaired? As your double glazed windows age, it is not uncommon for a sash to drop or hinges to become worn. If you notice air or water coming in around the sash, it may be that the window no longer closes properly. Use a credit card to check for gaps around the sash and replace hinges or adjust the sash accordingly until the seal is tight again. If the sash looks flush, it may be that the weather seal around the glass unit has gone. This can be replaced but you might consider upgrading your double glazing at this point to the latest standard. Finally, if you can feel a draught between the brickwork and the frame, it’s likely that the sealant has perished. You should be able to fix this by simply filling the area between the wall and the frame, or hiring a professional to do it.
• Can you just replace the glass in double glazing? If your glass is scratched, you will probably be able to polish out the imperfection relatively easily. If you have more significant damage to your glass work, such as a crack or a hole, it will need replacing, as sooner or later the gas cavity will be compromised. The good news is you can just replace the glass in double glazing, so this won’t be a complete refit. Similarly, anything more than cosmetic damage to the frame will also leave the glass, and your security vulnerable, so replacing the frame might be your only option.

But don’t let this talk of failures and repairs put you off; today’s double glazing units are stronger, better and more effective than ever before and will almost certainly come with a guarantee. They are built to last, and are arguably less likely to fail than single-glazed alternatives due to the huge development and investment they receive from the industry (only 7% of households in the UK now have no double glazing).

We hope our guide through the history, construction and benefits of double glazing has convinced you that it really is an investment worth making. Why not take a look at our huge range of double glazing solutions and see how we can start saving you money today?