Double Glazing

How does double glazing work?

Glass is a great conductor of heat, therefore with single glazing, much of the heat from inside the house literally goes out the window.

A double-glazed window uses two panes of glass, separated by a 6-12mm gap which is filled with air (or an insulating gas such as Argon Gas). As air is a poor conductor of heat, significantly less heat is lost through a double glazed window.

Double Glazed windows are also known as an Insulating Glass Unit (IGU).

Retrofit double glazing involves the removal of the existing window glass and the replacement with a high performance sealed IGU.

If timber is used, the window frame is modified in-situ and fitted with the unique Thermawood Retrofit Double Glazing System with new glazing beads.

If the window frame is aluminium, it is provided with a set of frame adaptors and the replacement of opening sashes.

All the double glazing Thermawood Otago installs is indorsed by the Insulating Glass Unit Manufacturers Association. IGUMA sets the industry standards of quality and performance of double glazed units. Only members of this association are regulated by these standards.

Benefits of Double Glazing

Improved Insulation

Double glazing provides efficient insulation for significantly improved thermal retention. Warmer in winter, cooler in summer. Teamed with high performing insulation, the Thermawood Retrofit Double Glazing System can create an optimal, well ventilated environment that has a high level of Indoor Air Quality (IAQ). The World Health Organisation recommends that the optimal indoor temperature for good health should be between 18ºC and 21ºC.

For the greatest thermal performance, we recommend using Low E (low Emissivity) Glass and Argon gas in the IGU. (See below for more on these products).

Reduced Condensation

Condensation forms when warm air containing moisture meets a cold surface. Cold enough for dew point to be reached. Double glazing enables a thermal barrier to form between your home interior and the cold moist air outside. Therefore, condensation is dramatically reduced. On some South facing windows, you may notice condensation forming on the outside of the window – highlighting the efficiency of your double glazed windows.

Added Value

The proven benefits of double glazing have meant astute buyers are expecting double glazing as a feature of their new property. Your home will become more desirable when it comes time to sell your property, and with the Thermawood Double Glazing system, the original character is still maintained and thus the architectural aesthetics of your home are not compromised.

Environmentally Friendly

Double glazing can reduce your energy consumption, saving money and assisting in saving energy. Many older homes use more energy to both heat and cool due to poor insulation qualities. Double glazing can substantially reduce energy cost and consumption by retaining heat during winter and by staying cooler during summer.

The Thermawood Retrofit Double Glazing System is produced locally in Mosgiel using recycled milk bottles. The system is environmentally sound which, is something we take great pride in.

Reduced Noise

Double glazing helps reduce noise levels in the medium to high frequency range (such as voices). An even greater degree of noise reduction can be achieved by choosing laminated/acoustic glass. (See our product info for more on these products).

Increased UV protection

With the use of laminated glass, you can cut out 99% of UV rays to help protect damage to furnishings. Please contact us for more UV reducing glass options

Performance and Lifespan of Double Glazing

The performance of double glazing depends on a number of factors including glass type and insulating property (Standard air v Argon gas) used, so it is import to consider what your requirements are before starting.

The performance of double glazing is directly correlated to the integrity of the seal around the IGU itself. The seal is what keeps the airspace (or Argon gas) contained within the two panes of glass, therefore the seal needs to be kept free from moisture. The breakdown of the seal becomes visible when moisture starts to appear in between the two panes of glass – causing the double glazing to fog inside. Fog inside double glazing cannot be fixed, the whole double glazed unit will need replaced.

The Thermawood Retrofit Double Glazing System is the only system that provides complete, concealed ‘drainage’ – it is the unique ‘dry’ glazing system. This adequate drainage prevents the breakdown of the seals and the integrity of the IGU’s.  

The Thermawood Retrofit Double Glazing System provides reassurance you will get longevity from your double glazing, no matter what the conditions.

Enhancing the Performance of your Double Glazing

The inclusion of Low Emissivity (Low E) Glass offers greater thermal performance to your double glazing and should be considered especially in the colder climates zones throughout NZ. Low E glass improves the insulating performance of the Insulated Glass Unit (IGU) as it traps the heat inside the building.

The performance of an Insulated Glass Unit (IGU) in reducing heat loss can be enhanced even more by careful consideration of airspace thickness and/or by using Argon Gas. Larger airspaces 12 - 16mm provide better insulation than the minimum 6 and 8mm and it is always advisable to achieve the 10mm or wider airspaces to maximise the insulation performance of the IGU (Note: 8mm minimum airspace required for Argon Gas filling). By using Argon Gas especially when you are limited to a minimum airspace in some frames it will provide better insulation than air.

Insulating Glass Unit (IGU) type

Heat Loss Reduction

(Dependent on glass thickness and airspace between the panes of glass)

Low E and Argon

71% – 77%

71% – 77%

47% – 54%

Single Glazing (1-4mm clear glass)

0% – 1%

For more information or technical specifications please contact us

0800 2 GET GLASS


03 4884000

71 Maclaggan Street, Dunedin


©2017 Thermawood Otago Ltd