Most people assume the gap between the panes of a double glazed unit is just air. In many modern units, it is filled with an inert gas instead, most often argon and sometimes krypton.
You cannot see the gas, but it makes a difference to how well the glass keeps your home warm.
Why fill the gap with gas?
Heat travels across the cavity between the panes, partly by moving through the gas and partly by the gas circulating in the gap. Argon and krypton are heavier than air and conduct heat less well, so they slow that heat loss down.
Both gases are colourless, odourless, non-toxic and do not react with anything, so they are perfectly safe.
Argon
Argon is by far the most common choice. It is relatively inexpensive and gives a useful improvement over air in standard units. Combined with Low E glass, it is what makes most modern double glazing perform as well as it does.
Krypton
Krypton insulates better than argon, especially in narrow gaps. That makes it useful where space is limited, such as slimmer units for older frames, and in some triple glazing. It costs more, so it tends to be used where those benefits really count.
Does the gas leak out?
Over many years, a small amount of gas slowly escapes through the edge seal. That is normal, and a well-made unit keeps the great majority of its gas for a long time.
When a seal fails completely, the gas escapes and damp air gets in, which is when the unit mists up. At that point the unit needs replacing. See why double glazing mists up.
Which should you choose?
For most standard windows and doors, argon-filled units with energy efficient glass are the sensible choice. Krypton is worth discussing if you need a slimmer unit or want the best performance from a narrow gap.
We make our own sealed units, so tell us about your frames and we will recommend the right specification. Contact us for a free quote.
