Which window? Double or triple glazing?

Hm, this really isn’t much...

In our construction specification, the chapter on windows alone was a whole A4 page long and contained both the type of glazing, as well as the U-values of the glass and the entire window, the structure of the frames, etc.

How extensive is the entire construction specification?

In my opinion, the entire construction project stands or falls with the construction specification. You can only demand what is definitely stated there.

Statements like "quality windows from well-known manufacturers" are vague and don’t really say much...

I can therefore only join the question from : Have you already signed the contract?

Hello,

We are planning to build a KfW 70 bungalow using solid construction. The living area will be approximately 130 sqm.
In the preliminary discussion, the topic was hardly addressed; we only stumbled upon it during the building application, that for our project "only" double glazing is planned.
But now we have been reading more and more often that triple glazing is already the standard, even with our developer.

To begin with: KfW 70 no longer exists; today there is _only_ the Energy Saving Ordinance, KfW 55 and better. Since you are in discussions regarding the building application, it means it has not yet been submitted.

Without triple glazing and professional installation thereof, in my opinion you will not be able to meet the requirements of the Energy Saving Ordinance 2016. You _do not have_ to calculate that, in my opinion you also cannot.

However, I assume that you have already signed the contract. Only what is stated in the contract and the attachments counts. So if triple glazing is _only_ mentioned on the homepage but not in the contract and attachments, you will _only_ be able to purchase these better windows at an extra cost.

Rhenish greetings from on the road

We have double glazing! Built in 2014, just missed KfW 55. And no: we don’t have window shutters. Maybe we pay 100 more per year according to @BeHaElJas’s calculation?!... Who knows? Projected and taking the surcharge compared to triple glazing, I come to the conclusion: we probably can’t make up the surcharge through savings in heating costs. So if the house is compliant with the double glazing energy saving regulation, you don’t need to lose sleep over it. Otherwise, I refer to @Epis’s posts.