Glass windows connect us with the world around our homes, while keeping the worst of the weather at bay. The thin, transparent surface of the single pane of glass has one significant downside – it’s a terrible insulator. In fact, it amplifies the effect of the heat from the sun, and the larger the window, the more noticeable it is. During winter, your appliances will need to work extra hard as the process known as conduction allows your precious heat escape out through the single glass window pane. This issue gives rise to a common question – can you retrofit an extra layer of glass on top of the old existing one to improve the insulating properties? This is referred to “double glazing”.
How Does Double Glazing Work?
Double glazing functions by incorporating two glass panes separated by a gap of around 12mm or more, typically filled with an insulating gas such as argon. Argon is an inert gas, meaning it doesn’t easily react with other chemicals or gases. Argon is much denser than air and has a far lower heat conductivity – approximately a third less than air. The insulating gas and the gap between the panes act as barriers, reducing sound and excessive heat from the outside. Well-insulated window frames are also necessary in order to not diminish the insulating effect of double glazing.
Additionally, some double glazed windows have a low-emissivity (low-E) coating. Low-E coatings will minimise the amount of ultraviolet and infrared light that can pass through glass without changing the amount of visible light that is transmitted. When heat or light energy is absorbed by glass, it is either shifted away by moving air or re-radiated by the glass surface back into the surrounding environment.
How Much of a Difference Does Double Glazing Make?
Double glazing offers numerous benefits that make a noticeable difference to a building’s level of comfort and energy efficiency. According to Sustainability Victoria, double glazed windows can reduce heat loss or gain by about 30% compared to single-glazed aluminum windows.
In addition to improving the R-value performance of the overall wall system in which the windows are installed, double glazing makes a real difference to acoustic noise levels, reducing the levels of outside noise intrusion, and improving privacy for the residents of the home. It also helps reduce condensation buildup on windows, particularly in colder weather. In Australia, the main benefits of double glazed windows will be felt during the hottest months of the year. Just place your hand up close to a single pane window on a hot day and notice the amount of heat radiating through the glass surface!
Can I Double Glaze My Existing Windows Myself?
While it’s technically possible to double glaze existing windows through several DIY methods or retrofitting options, it’s generally not recommended. The process can be complex and challenging, requiring specialised tools and an experienced hand to ensure proper installation. DIY double glazing can also weaken the structural integrity of the windows if not done correctly. Professional installation will almost always offer a neater finish and a higher quality result. A professional window installer should also be in a position to offer warranties and guarantees on their work and materials supplied, providing peace of mind and protection against potential issues which may crop up in the future.
Are there Any Downsides to Double Glazing?
While double glazing existing windows offers significant benefits there are a couple of downsides worth mentioning. The most obvious downside would be the cost of installation. Also, double glazing is not entirely risk free. Over time, some double glazed windows have been known to develop seal failures, leading to moisture buildup and fogging up between the panes. In addition, some individuals may prefer the aesthetic of single-pane windows, especially in historic properties.
Alternatives to Double Glazing Existing Windows
If double glazing your existing windows is simply not an option for you, consider some of these alternative options:
Window tinting is an alternative to double glazing existing windows as it provides a layer of film that helps reduce glare and UV radiation. While it doesn’t offer the same level of insulation as double glazing, it will block unwanted sunlight glare and reduce the need for air-conditioning during summer. Window tinting increases privacy during the day and costs far less than retrofitting an extra layer of glass to your existing windows.
Interior blinds are also effective at blocking sunlight, reducing temperature gain and may offer complete visual privacy when closed. While interior blinds come in various styles, materials, and opacity levels, they are most effective against radiant heat when the surface of the blind that is facing the window has a reflective coating. When combined with an air-gap of a couple of centimeters, reflective surfaces will reflect not just the light but also the radiant heat back toward the source of the heat.
Exterior blinds are also a traditional yet popular alternative, blocking direct sunlight before it hits the window glass. Exterior blinds come in different styles and materials and can be raised and lowered manually or via a motorised system.
Replacing Existing Windows with New Double Glazed Windows
This is by far the best solution if you can afford it. If retrofitting the window glass isn’t your cup of tea, and if your budget doesn’t allow you to replace all of your window glass with the double glaze variety, consider which windows are responsible for the most heat gain during summer time, and replace these first.
Top of the priority list would be the largest windows which are exposed to direct sunlight for the longest period of time throughout the day. If you are checking this out during winter, remember that depending on the design and layout of your house, the windows most exposed to the sun during winter may not correlate with those which receive the most direct sun during the summer months. Contact a reputable local glass installation company, ask them about warranty periods, and make sure you file away a copy of the invoice for their work.
Upgrading your windows to the double glazed variety is one of the many things you can do to better insulate your home and cut down on your energy bills. Other upgrades you may like to consider are removal and replacement of any damaged insulation, or the installation of a whirlybird on the roof of your house.