Triple Glazing

What is it & is it worth it? The figures are black and white!

Triple Glazing is the introduction of a 3rd pane of glass to your windows, creating an extra cavity which is supposed to improve the U Value of the glass unit.

Is it worth it?

We don’t think so

We can and do supply triple glazing where customers really want it.

Double glazing is better than single glazing right? (YES!)

In that case triple glazing must be better than double glazing? (well not always)

The main difference in high performance double glazing vs triple glazing is the makeup of glass types in the glass unit, width of cavity and whether Argon gas has been injected into the unit during manufacture or not.

Our double glazing is made up of : 4mm extra clear glass / 20mm 90% argon filled cavity / 4mm ClimaGuard A+ 

However the cost difference vs savings is minimal. The Glazing industry is an ever changing landscape and we have seen massive changes in the technology in double glazing which puts it almost on an even par with triple glazing.

With Argon filled cavity glass units, thermally efficient reinforced Multi Chamber PVC profile, warm edge spacers and Low E glass coating. Double glazed units can actually help reduce on heating bills by absorbing natural sun light and reflecting heat back into the home . Something that is not as achievable with triple glazing due the extra pane. The extra pane also cuts down the amount of natural light into the property.

Triple glazing is often sold to people on its reduction of noise, yes that extra cavity can help reduce noise and can be a big selling point. Although if its sound deadening your after, why not look at acoustic glazing, this is not something new, just never really asked for until the advent of triple glazing. Acoustic glass is  specifically designed to reduce / block noise.


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Double Glazed Units

Made up of 2, 4mm panes of glass with Low E coatings Toughened if required (We can also provide acoustic glass used for sound deadening to same achieve the same overall thickness)

UPVC Window Double Glazed Unit

Triple Glazed Units

High performance triple glazing requires 2 panes of low e glass, made up as: 4mm clear/4mm low e/4mm low e. It is recommended by the manufacturers that this middle low e pane is toughened to prevent Thermal Stress Cracking.

UPVC Window Double Glazed Unit

Double Glazed - Glass Make Up



4mm clear glass/20mm Argon/4mm Planitherm Total+

1.2 W/m2.K


4mm clear glass/16mm Ar/4mm Planitherm One



Triple Glazed - Glass Make Up



4mm clear glass/8mm + Ar/4mm clear glass/8mm + Ar/4mm Plan T+

1.3 W/m2.K


4mm clear glass/8mm + Ar/4mm Plan T+/8mm + Ar/4mm Plan T+

1.0 W/m2.K


4mm clear glass/8mm + Ar/4mm Plan 1/8mm + Ar/4mm Plan 1

0.9 W/m2.K


4mm clear glass/10mm + Ar/4mm Plan T+/10mm + Ar/4mm Plan T+

0.9 W/m2.K


4mm clear glass/10mm + Ar/4mm Plan 1/10mm + Ar/4mm Plan 1

0.8 W/m2.K


4mm clear glass/12mm + Ar/4mm Plan T+/12mm + Ar/4mm Plan T+

0.8 W/m2.K


4mm clear glass/12mm + Ar/4mm Plan 1/12mm + Ar / 4mm Plan 1

0.7 W/m2.K



Ar = Argon gas @90% concentration


Therfore it can be proven that:

  •  - A Triple Glazed Unit can be less effective than a Double Glazed Unit (Depending on Glass Unit make up)
  •  - Wider gas filled cavities giving wider over all unit thickness can achieve significant improvements in lowering U-values

The cost of triple glazing dictates that to achieve overall energy savings, correct triple glazing needs to be specified and wider cavities are required.


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