Double or triple glazing in new buildings - triple glazing allegedly unnecessary expense

I consider the idea of double glazing (in the south) (and thus possibly making sliding doors easier) quite reasonable; this would have to be considered on a case-by-case basis.

I see it differently, see also "Are three window panes better than two?" (not linkable here, but easily googlable with quotation marks), for this I also recommend the sister article on the topic "warm edge," in which ...

... however, are not yet mentioned. The term is probably also a protected trademark – how far the concept is patented, I have not yet researched. But I do not see it as a fundamentally new reinvention of the wheel.

Swissspacer = a very well-known manufacturer in expert circles for thermally improved insulated glass edge seal = warm edge = definitely sensible = significantly less condensation at the glass edge and energy savings = at low additional cost. Today I would always choose windows with triple glazing with Ug 0.6.

I would always choose windows with triple glazing with Ug 0.6 today.

I would also choose triple glazing. It’s somehow standard these days... I think. We ordered our windows from a friend who is a window dealer in Poland. They are aluminum windows from Aliplast (Belgian manufacturer). For the Polish dealer, it was a given that all windows get triple glazing (Ug 0.5!), warm edge from Swissspacer. They are installed according to RAL on "warm window sills" with Illbruck compression tapes. All floor-to-ceiling windows also receive a Purenit base instead of doubling the frame. I thought if all this is already understood as standard in Poland for self-installation, it has long been the case in Germany...

You can do the calculation yourself. Simply put, we compare only Ug (i.e., the value of the glass alone). The heat output through this window area is the product of area, temperature difference, and U-value. 5 large double windows (e.g., terrace) each 4 m² give 20 m² of glass area. With 20°C inside and -5°C outside, there is a 25 K temperature difference. U-values are given (as said, we simply take only the losses through the glass area, i.e., Ug). 20 m² * 25 K * 0.6 W/(m²*K) = 300 W or 20 m² glass area * 25 K * 1.1 W/(m²*K) = 550 W. You have to heat the difference of 250 watts more, i.e., over a (constant -5°C cold) 24-hour day 250 W * 24 h = 6000 Wh = 6 kWh. Now the temperature difference is not constant, but you can look up how large the accumulated temperature difference is depending on location (search for Heizgradtage, "Gradtagzahlen-Deutschland.xlsx" or similar). Let’s assume a typical German value of 3500 K*d = 84000 K * h. Then the total heat loss for the 20 m² glass area with Ug=0.6 would be 1008 kWh per year and with Ug=1.1 would be 1848 kWh per year, i.e., 840 kWh more. What do the 840 kWh of _additional_ heating energy cost you? With gas it’s a relatively simple calculation, with a heat pump it might be trickier if its efficiency varies sharply depending on outside temperature. With your location (warmer by the sea, colder in the low mountains) and window area, you can calculate yourself; it’s sufficient to calculate with the Ug difference of 0.5. But the 50 € is certainly far too little, even with pre-war gas prices that still wouldn’t work. The specialist advisor/salesperson probably still has to sell a few double-glazed windows. Best regards

Many thanks again for the many statements! We will probably go with the triple after all.

for the detailed calculation!

So I wouldn’t skimp on the glazing either, I think you made the right decision there.

In our old building, we replaced our double-glazed windows with good triple-glazed ones and the difference is significant. Only in the attic did we choose new roof windows with double glazing. Since we only sleep up there and still have shutters for heat and cold, that is sufficient.
On the ground floor, the last 3 new windows will finally be installed soon and I am looking forward to it because there really is a difference. Admittedly, I am talking here about double-glazed windows from the 90s... but I believe with 3 panes you simply achieve more, even or especially today.

Although I am talking here about double-glazed windows from the 90s... I believe you simply achieve more with 3 panes, even or especially today.

There are very different types of glass, which is why double glazing does not necessarily have to be worse than triple glazing (for trademark reasons, I am temporarily not providing any references to my external posts).