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Different Types of Double Glazing Units

Two panes spaced apart have been know to give better insulation than just one pane for over a 100 years a Norwegian explorer, Nansen had his cabin skylight triple glazed in the 1893, though the American patent office claim double glazing was invented in the 1930’s.  Anyway it made it way into Upvc windows and there are lots of different variations.

The basics
A double glazed unit or sealed unit comprises of two panes of glass separated by a bar called a the spacer bar the perimeter of the spacer bar has an adhesive sealant applied during production.

The Sealed Unit (SU) is custom made to order to fit the glass rebate size of the upvc window,door etc so glass made for one window will not fit another unless they are the same size. Phone Box UPVC

What’s safety glass?

Float glass when broken makes razor sharp shards not good if you fall through it see low level glazing regulations so the float glass is put through a tempering furnace the result is toughned safety glass which when broken shatters into tiny fragments which are unlikely to cause death.As used in car side windows and phone boxes (little b*stards).

Laminated high security glass
Another type of safety glass is laminated glass as used in car windscreens this is a high security glass it has a “plastic” interlayer 0.38mm thick sandwiched between two sheets of 3mm glass overall thickness 6.4 nominal you can then choose another type of glass for the other pane in your double glazing .The laminated pane will stay intact when the glass is broken its very tough stuff.  It forms the basis for the glass in front of the bank teller which has about 5 laminated layers so its bullet proof!

Its a great choice for the large panes in ground floor windows at the rear of the house if your really concerned about security. You can order it with your window order online.Another often overlooked aspect of laminated glass is that it has excellent soundproofing thanks to two different thickneses of glass 6.4mm/4mm and the interlayer stops 99% of UV rays ie you will not get a suntan but your furnishings will fade a lot less.

Spacer bars
Aluminium bar is used mainly but in the quest for lower U values (which are measured in the centre of the glass pane) composite spacer bars are now being used in high performance sealed units.The aluminium spacer bar can act like a thermal bridge between the two panes of glass when there are extremes of temperature from the room to outside.Composite bars reduce this effect as they are better insulators and also come in a range of colours see here.

Gas filled units
The sealed unit as you might expect is normally filled with air and hermetically sealed (ie air tight) Argon gas is more dense than air and offers less thermal conductivity via convection currents it gives a small decrease in U value and offers a slight reduction in noise levels when used in double glazing.

Spacer bar thickness an old double glazing salesman chestnut about the wider the spacer bar the better than performance true up to a point 16mm is seen as the optimum 20mm though is the industry standard the difference between the two thicknesses is negligible.

Blinds inside the glassUPVC Doors
Amazing but true we can put Venetian blinds inside the space between the two panes they come in a variety of colours and can be operated electrically or by a draw cord to tilt and go up and down inside the unit.They come in a range of colours and never need dusting!  You can’t order these online please contact us for a quote you can see them in display at either Coventry or Birmingham showrooms.

Self cleaning glass
We can supply the full range of Pilkingtons Activ range of self cleaning glass we didn’t believe it eitherPilkington Double Glazing but after 3 years in our Conservatory in Coventry it’s amazingly clean and no ones ever actually washed it go to our Pilkingston Activ page to learn more.Please contact us for quote for this special glass.

The U or insulation value
U value is the insulation value of a material .A cavity brick wall has a U value of approx 1.5w/m2 k.

The lower the U value the better the insulation value of the sealed unit and the lower your potential heating bills for example one pane of float glass has a U value of 5.5 a double glazing unit with two panes of float glass has a U value of 2.7 the most commonly used unit to achieve the U value of 1.8 is Pilkington's K glass.

So its quiet an improvement on the 2.7 of the old sealed unit you can buy units with U values as low as 1 below are the different types available from ufit.

Note after October 2010 you will need an energy rated window see link which will make U values Redundant. See our energy rated windows page.

Pilkingtons K glass U value of 1.8 this unit is made up of one pane of float glass and one pane of K glass on that faces the room ( there’s a label saying which way round to fit it)

Pilkingtons K glass with argon gas U value 1.6 Argon gas is pumped in between the two glass panes Argon gas conducts heat more slowly than air hence the reduced U value.

Energy Saving Double GlazingEnergy + has a U value of approx 1.1 Energy + is our own brand that we have developed it’s a pretty exotic list of components; super composite spacer bar, Argon gas, Softcoat low iron glass you can order this option online with your window order.