Double glazing is found in offices, homes and government buildings across the world, thanks to its remarkable insulative properties.  It will considerably outperform a single, ordinary pane of glass in impeding the flow of heat, and for this reason it’s a weapon of choice for homeowners looking to reduce their bills during those icy winter months.

But does double glazing keep heat out as well as in?  The answer is yes: a less often-touted benefit of double glazing is that it’ll help keep your home cooler in summer – which is invaluable if we’re to get a good night’s sleep during those July heat waves.

sun through window

How does double glazing work?

Double glazing works by limiting the amount of heat energy that can transfer from one side of the window to the other through convection.  It does this by placing two separate panes of glass parallel to one another, and leaving an empty space in between.  When one side of the glass becomes hotter, its molecules begin to vibrate very quickly, causing a chain reaction that spreads across the solid glass.  But this heat energy is unable to pass through the empty space on the other side, since there are far fewer particles through which to transfer the energy.  The heat is thus slowed down.   This effect is even more pronounced in modern forms of double glazing, which substitute empty space for a vacuum, or an inert gas like argon.

How do I compare different sorts of double glazing?

In order to see how effectively your window will contain heat (and noise), check its energy efficiency rating.  This score is presented on a scale of A+-G, with A+ being the best and G being the worst.  While a window’s rating will indicate its real-world performance, this performance will be impacted if the window suffers damage over time.

When the seal around the edge of a double-glazed window breaks, the gas trapped inside will be able to escape.  This effect becomes especially obvious during winter, when water droplets begin to condense between the window panes.  This is evidence that water vapour has found its way in through a gap, which means that the gas inside your window has escaped.   This will vastly reduce its ability to repel (and contain) heat, and so the window will need replacing.  Fortunately, this sort of wear-and-tear takes many years to manifest, but with the right maintenance, the day of failure can be delayed considerably.

How else can I keep my property cool during summer?

Of course, double-glazing isn’t the only way we can prevent heat from entering our homes.  In hotter climates, it’s common practice for windows to be fitted with shutters, which block heat from entering the house.  For obvious reasons, this is less common in the UK, but we can apply the same principle and close our curtains or blinds when the sun is beating down on the sides of our houses in the height of summer.

Looking for new windows for your home? Browse our sliding sash or casement windows or find out about our handmade bespoke windows.