Benefits of Double Glazed Windows

Windows provide the least resistance to the flow of heat than any other building element. The lowest surface temperature inside a home occurs on the windows. Maintenance of relative humidity is limited by condensation. For these reasons, homeowners install double glazed windows to reduce the loss of heat and increase the relative humidity.  They are a great way to minimise noise and save energy. Double glazed windows mean a more comfortable home environment.


Double glazed windows are insulated glass units that combine two glass panes into single window systems. The panes are separated by a spacer and a layer of still gas or air. The panes are fitted into frames made wider to accommodate them.

The space between the panes ranges from six to 20 mm. Optimal thermal performance needs a minimum of 12 mm of space. The sealed space acts as insulation. It limits the cold air entering a home. A gas filled space increases acoustic and thermal performance. Argon is the most popular gas. Its low conductivity properties improve insulation.

The spacers are polymer or metal strips that separated the panes. They remove trapped moisture from the air space. Different glass types are used in double glazed windows. Laminate and Low-E glass further increase noise control and energy efficiency.

The thermal properties of double glazed windows depend on both air space and sash characteristics. Window limitation recognition is needed in maintaining the humidity in a building. Various factors affect thermal performance.

They include:

  • Amount of recessing
  • Location
  • Proximity of heating outlets
  • Degree if forced convection
  • Arrangement of drapes or blinds

Single and Double Glazed Window Comparison

Single glazed windows are responsible for a lot of wasted energy. Being close to a single glazed window is often uncomfortable. In summer it is too hot, in winter too cold. The belief that the window is not tight is a misconception. The problem is insufficient glazing. Double glazed windows outperform single glazed windows significantly in several areas.


The overall heat transfer is a denotation expressed as the U-coefficient or U-factor. It describes the energy conducted through building components and materials under standardised conditions. A low U-value indicates a better thermal insulation than a high U-factor. Single glazed windows have a U-factor of  5.9. The U-factor of double glazed windows is 1.1.


Single glazed windows do not have Low-e glass. Double glazed windows do. Low-e is a technical optimisation and enhancement. A nanometer-thin noble metal coat is burned into the inside surface of the outer pane. The layer is so thin it cannot be seen with the naked eye. Visible light passes the layer. Most infrared light reflects back to the outside. The objective of the process is to ideally keep internal temperature constant without a heater or air-conditioner.


The amount of solar radiation passing through a window has an SHGC rating used to quantify window energy efficiency. Single glazed windows have an SHGC of 86 percent. The SHGC of double glazed windows is 63 percent.


Windows, having a lower SHGC rating also have less Visible Light Transmission, or VLT. The VLT of a single glazed window is zero. Double glazed windows have an VLT of 80.


The three most common reasons that double glazed windows are installed are the cost and energy savings and the prevention of condensation. Double glazed windows form a barrier between the outside environment and the interior of a home. They reduce the entry of sound from the outside and internal noise does not reach the outside.

Because double glazed windows are hard to break, they increase the security of a home. They are sealed tighter than other windows. The seal makes forcing them open a tough task. Damage to furnishings is reduced. Double glazed windows reduce the amount of heat and sun that enters the house. Carpet, furniture, paintings and other household items are protected from sun damage.

Of all the benefits of double glazed windows, the most significant are the insulation properties. They reduce heat loss. They also stop heat entering the home in summer. The insulation properties save a significant amount on cooling and heating bills. Reduction of ambient noise entering the house is an added perk.

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