Triple Glazing

leveller2911

Mr.Generous wrote: »

The bigger the gap in a sealed unit the better the sound insulation I have been told, there must be some advantage as the early units were on typically a 12mm bead whereas now 20mm or larger is the norm. How would argon filled K glass compare to triple glazing cost wise and insulation wise?

Thats not correct as sound travels easily through air. What does make a difference is having different thicknesses of glass so typically 6mm outside pane and 4mm inside pane. You can get acoustic glass which has a coating I believe but Ive never used it.

As I posted previosuly when the air gap goes above 12mm its actually no better.

As an example if you have 2 sealed units ,both with 4mm Softcoat Low E glass as the inside pane and clear 4mm glass on the outside pane and both filled with krypton . The one with an air gap/spacer of 10mm wide will have a U value of 1.1 but if that space is made wider and 20mm wide the U value goes up to 1.2.The idea being a lower U value is more efficient so its not alway true that increasing the spacer makes it more thermally efficient.

If there is no gas in the unit at all then the air gap does make a differnce. the difference between a good DG unit and a good TGU really isn't much of a cost saving and as with DG they will need to be replaced eventually.

malc_b

A few other points to consider for DG vs TG. 1st, Weight. TG is 50% heavier so large windows, patio doors, etc. become harder to open and close. 2nd, it is a good idea to understand what the A,B,C rating is all about. Modern windows have coating so the they have a thermal gain due to the sun. There is some magic formula that calculates this which I assume takes an average since there can't be a thermal gain from a north facing window, can there?

So a C rated is a loss of -10 to -20 kWh/m2/yr. In other words if you have 1m2 window and you pay 5p a unit for gas then over a year a C rated window will cost 50p - £1. B is 0 to -10, i.e. 0 - 50p cost. A is 0 to +10 so that 0 to gaining 50p off your gas bill. A+ is 10 to 20, so 50p to £1 off your gas bill. A++ is 20 to 30 so £1 to £1.50.

Because of this solar gain a TG window can actually have a lower ABC rating than a DG window as the extra pane cuts down the light through put and the heat through put, even if the U value is better.