Double and triple glazed windows

Whether you’re designing a new build or looking to renovate an existing home, glazing massively impacts the aesthetic of a home, but it is also crucial to consider the thermal efficiency of the different options.

Glazed windows gives personal touch to the cafeteria

Single glazed windows no longer meet building regulations on thermal performance, therefore double glazing is today the most popular form of glazing.

In double glazing windows the two glass panes are inserted in parallel separated by a cavity filled with gas which has an insulating effect.
Triple glazed windows simply use three panes of glass within a sealed frame, instead of two. So, although glass conducts heat fairly well, double and triple glazed windows reduce this heat loss using the layers of air/gas in between the panes making it a lot harder for heat to escape.

Glazing’s energy efficiency can also be improved by opting for low emissivity glass (aka Low-E glass). Low-E glass has an invisible coating that dramatically reduces heat transfer and reflects interior heat into the room. Low-E glass can make a big difference to a window’s thermal performance, whether it’s double or triple glazed.

It can be difficult deciding whether to choose double or triple glazing windows and doors, since each of them carries their own benefits. You can read all about double and triple glazing benefits on our dedicated post 


Choosing the best glazing option for your project

All VELFAC windows are double glazed as standard, and deliver impressive thermal and acoustic insulation, which can be further improved with triple glazing.

We also provide a wide range of glass options, with the result that every window can be tailored to meet energy needs, deliver precise acoustic control, guarantee privacy, and increase security. All double glazed windows within the VELFAC Glazing concept are EN 1279 compliant.

In doubt about choosing double or triple glazing for your project?



Double and triple glazed units

VELFAC 200 Double glazed windows


With U-values as low as 1.47 W/m²K, VELFAC double gazed composite aluminium / timber windows and patio doors feature uniform sightlines, whether fixed, opening or motorised, to deliver a clean, uninterrupted exterior finish. Recessed installation also delivers a 'floating' sash, adding to the contemporary finish.

VELFAC 200 Triple glazed units


Identical in design to our double glazed units, triple glazing can reduce U-values to as low as 0.8 W/m²K and are ideal for installation where improved thermal performance or acoustic control is essential. As VELFAC double and triple glazed windows feature identical sightlines, units can be combined without any impact on overall design, or on exterior facades, allowing precise thermal and acoustic control across a building.


A range of glass options

Specifying the right glass is an important way to ensure your windows deliver the level of performance you need – whatever their location. To improve performance, VELFAC glass options include:



VELFAC CLEAR glass (the standard option) delivers a light-filled interior and a clear view of the outdoor. Excellent insulation results from a heat-reflective coating applied to the inner glass surface, and the use of argon gas within the glazing cavity.

A standard VELFAC 200 double glazing window measuring W1230 x H1480mm with CLEAR glazing, achieves a U-value of 1.47 W/m²K. For even better insulation, you can choose a VELFAC ENERGY unit, which feature a combinations of triple-glazing, argon gas filling and a ‘WarmEdge’ spacer, that can achieve U-values as low as 0.80 W/m²K.

VELFAC SUN - solar control


In full sun, windows can generate a lot of heat (known as solar gain), especially if units are large or installed on south or west facing facades. VELFAC SUN25 glass features a neutral coating which reflects up to 60% of the sun’s heat while allowing plenty of natural light to enter the room. For additional solar control, VELFAC SUN35 features a slightly darker coating which (although transparent) will slightly affect the appearance of external colours.

VELFAC DÉCOR - opaque privacy glass


If privacy or security are essential, VELFAC DÉCOR opaque glass is the ideal choice. VELFAC DÉCOR is available in five different designs, including matt foil lamination to give a sand-blasted appearance and reduce risk of injury if the glass is broken. To ensure excellent performance of the VELFAC window unit, we recommend that VELFAC DÉCOR glass is installed as the external or middle layer when combined with VELFAC CLEAR, or as the internal or middle layer when used with VELFAC SUN.

VELFAC SOUND - noise reduction


Efficient glazing is fundamental to noise control, and although double glazing can reduce external noise, thicker or different combinations of glass can significantly improve acoustic performance. The Rw rating indicates the number of decibels by which a window unit will reduce apparent noise - a standard VELFAC double glazed window achieves Rw32, which can be increased to Rw41 by adjusting the thickness of the glass and the glazing rebate.

VELFAC SAFETY - safety glass


Safety glass must be installed where there is a risk of impact and injury (safe breakage glass), or where glass is used to create a physical barrier (containment glass). Depending on location and need, VELFAC SAFETY glass can be specified as either laminated or toughened. VELFAC SAFETY glass is designed to break harmlessly, to reduce the risk of injury, and can also provide additional security as it can withstand considerable force.

VELFAC SECURE - improved security


VELFAC SECURE glass is designed to minimise the risk of burglary by withstanding significant physical impact and resisting forced entry. In accordance with BS/EN 356 and BS/EN 1063, VELFAC SECURE glass meets the requirements of Class P1A to P5A (vandal-proof), Class P6B to P8B (burglar-proof) and Class BR1 to BR7 and SG1 to SG2 (bullet-proof).

VELFAC FACADE - coated glass for glazed facades


VELFAC FACADE glass is coated with non-transparent enamel to create glazed panels for visually uniform facades, for facades featuring special colour effects, or to conceal floor slabs or other internal structures behind a glass façade or window. VELFAC FACADE glass can also be used to create spandrel panels, fitted with 6mm glass, or look-alike panels – double glazed units usually combining external solar protection glass with internal enamel glass to allow closer colour matching with other windows in a facade

VELFAC FACADE glass is available in several RAL colours, and is supplied as toughened and heat-soak tested as standard.

VELFAC FIRE - fire protection


VELFAC FIRE glass is designed to be installed in areas which are designated as secure escape routes, or which are designed to protect persons or objects from fire; VELFAC FIRE glass meets European and International Standards, and has been integrity tested according to BS EN standards 1363-1/2, 1364-1 and 1634-1.