Double Glazing will Save Energy Costs.
Warmer in winter & cooler in summer.

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 Sydney 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!

Secondary double glazing has benefits beyond only reducing noise, sound proofing or sound reduction. Additionally, secondary double glazing decreases heat loss, has less condensation, eliminates drafts, and even raises the value of your home.

And because we completely seal around the frame of the new door or window, unlike occasionally with classic double glazing, there is never any gap between the frame and the walls, retrofitted double glazing has better insulating capabilities than traditional double glazing.

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 costs of energy used.

Window Seals

A window that allows air to flow around it, regardless of the materials used or the way it was built, will perform poorly as an insulator. There is a very good chance that windows with movable sashes will have gaps between the moving frame (sash) and the window frame.

The secondary double-glazed window frame will be entirely sealed, preventing any airflow around the window, greatly enhancing the window’s capacity for thermal insulation.

‘U’ Values

The rate of heat loss through a window, sometimes known as the “U value,” is the common way to gauge how energy-efficient a window is. The amount of heat lost through a window with a U value of 4.0 W/m2K is double that of a window with a U value of 2.0 W/m2K. You will lose less heat through your windows and your windows will be more energy-efficient if the U value is lower. Our energy-efficient windows are compared in the table below:

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 the unique draft proofing properties of Sound Proof Windows, it means that we provide the industry’s top solution for decreasing heat loss and sustaining cooling.


  • 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