Argon Filled Double Glazing

Energy efficiency is probably a relative term, but as a homeowner you can now gauge how efficient your double glazed windows are through a simplified rating system established by the British Fenestration Ratings Council (BFRC).

Under this system, an A-graded window would be excellent and a G-rated unit the least thermally efficient. There are of course several variables that go with the letter grade, and these include U value, energy rating, effective heat loss and solar gain. The most current building regulations stipulate that house windows have at minimum an overall rating of C.

It is common knowledge that spacers can be filled with either air or gas. Cost-wise, ordinary air-filled windows are the cheaper choice. However, when it comes to energy efficiency and performance, you will find argon-filled double glazing the wiser investment.

First, as an inert gas, argon is relatively nonreactive. This nonreactive property helps to ensure a longer shelf life for your window frames. Dry air is commonly a mix of oxygen, nitrogen, carbon dioxide and even trace elements of argon. However, more often than not, the oxygen component is a source of potential problems. Oxidation could give rise to issues such as rust and corrosion in double glazed windows that use metal framing.

Second, argon is more viscous than dry air. In general science, viscosity is equated with resistance to flow. The higher the viscosity, the greater the resistance, the slower the flow. Since molecular movement is inhibited in argon gas, the rate of heat transfer and heat loss are also reduced in the double glazing assembly.

Third, argon is denser and heavier than dry air. The higher density of argon makes the double glazing installation more resistant against convection currents and less prone to condensation. Condensation happens when air rises, then cools, so that gas reverts back to the liquid phase. By coupling argon's high density with desiccant and a very good sealing system, argon-filled double glazed windows will stand a better chance against moisture build-up.

All in all, the inert properties, high viscosity and high density of argon make the gas a suitable material for spacers in a double glazed window. Apart from the letter grade, proof is in the U values too. Regular argon-filled double glazing units with a 16 mm spacer have an estimated U value of 2.6. A lower heat loss measure of 1.6 can even be found in argon-filled assemblies that employ low-thermal-emissivity coated glass.

If you want to find out more about argon filled double glazing then click on the link to read an independent guide to the subject.

Sarah Clark is a freelance author who writes for many popular home & garden publications.

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