Double Glazing will Save Energy Costs. Warmer Winters, Cooler Summers.

Save on heating & cooling costs with secondary double glazed insulated windows
The highest quality secondary double glazing for window insulation to save energy costs

SoundProof Windows & Doors. Secondary glazed windows save energy costs



Our energy efficient window systems helps maintain your rooms temperature

The best energy saving windows and doors Melbourne has to offer.

Up to 40% of all heat loss in a home or building is through the windows. Our secondary glazing energy efficient windows can stop up-to two thirds the heat loss you are currently experiencing through your windows!

The advantages of Secondary Double Glazing include more than just reducing noise, sound proofing or sound reduction. Secondary Double Glazing also reduces heat loss, has less condensation, eliminates drafts and even increases your property value.

All this can be achieved for relatively little outlay, which is recovered over the years by lower fuel bills as a result of your energy efficient windows!

Studies by the Australian Glass and Glazing Association on new homes built by one of Victoria’s biggest home builders showed an average cost payback of glazing windows to be just over five years on average. Please note that payback periods will vary depending on the initial costs, the type & amount of heating &/or cooling and therefore cost of energy used.

Window Seals

It is also important to remember that a window allowing airflow around it will be a poor insulator, no matter what materials are used and its construction. Windows that have moving sections are highly likely to have gaps between the moving frame (sash) and the window frame.

As we completely seal the secondary double glazed window frame, there will be no airflow around the window, dramatically improving the thermal insulation properties of the window.

‘U’ Values

The standard method of measuring windows energy efficiency is via the rate of heat loss through a window, which is called a ‘U value‘. A window with a U value of 4.0 W/m²K will lose twice as much heat as one with a U value of 2.0 W/m²K. The lower the U value the more energy efficient is your window & the less heat you will lose through your windows. The table below shows how our energy saving windows compare:

Window Glazing Options Glass – Gap – Glass U value
Single glazing: 3mm – 0mm – 0mm 5.9 W/(m².k)
Double glazing: 3mm – 6mm – 3mm 3.4 W/(m².k)
Secondary double glazing: 6.38mm – 100mm – 6.38mm 1.9 W/(m².k)

The U values for our secondary double glazing as shown in the table above show that if you’re wondering how to reduce heat loss through windows, secondary double glazing is the clear winner!

And when combined with Sound Proof Window’s unique draft proofing properties, means that we offer the market leading solution for reducing heat loss, as well as maintaining cooling from air conditioning units in summer.



  • Luminous and solar characteristics of glazing: EN 410 (1998)
  • Determination of UV, light and total solar transmittance: ISO 9050 (1990)
  • Determination of the thermal transmittance: EN 673 (1997)

Light Factor

  • Transmittance LT 69%
  • Outdoor reflectance LRE 18%
  • Indoor reflectance 16%

UV Factor

  • UV Transmittance TUV 27%

Energy Factors CEN (EN410)

  • Transmittance TW 53%
  • Outdoor reflectance RE 17%
  • Absorption A1 11%
  • Absorption A2 20%
  • Solar factor g 0.69
  • Shading coefficient SC 0.79
  • Solar factor g DIN 67507 (m1) 0.68