ᐅ Window quotes as different as day and night

Investing 100 euros for a maximum reimbursement of 50 euros and ending up with nothing to show for it

I wouldn’t do that

I don’t want to say too much, but since it’s an old industrial building, what about heritage protection?

The windows were just measured again—especially the outer frame. It actually sticks out by 2cm (1 inch), not just 1cm (0.4 inch). So the plan is: 4cm (1.6 inches) of insulation on the left and right, make use of the 2cm (1 inch) projection, and reduce the width by 2cm (1 inch) on each side. This would result in a total loss of glass area of 4cm (1.6 inches) if the entire frame is plastered over.

haydee schrieb:
altes Industriegebäude wie sieht es da mit Denkmalschutz aus?

There is no heritage protection for it.

A 4 cm (1.5 inches) loss is not much. Unless they are actually loopholes.

In that case, it is fine, and it is one way to avoid insulation around them.

kaho674 schrieb:
Where can you find a person like that?

You can search for consultants in your area on the Energy Efficiency Experts website. Then you can check them out. Apparently, becoming an "energy consultant" is not particularly difficult and for many (I feel especially chimney sweeps) it’s just an additional source of income, since homeowners are required by KfW to involve a consultant. Our first one asked to be released from the contract when I brought up the airtightness concept...

kaho674 schrieb:
The windows are "masoned over" from the outside with facing brick. There is only a 1cm (0.4 inch) window frame there.

You mean the windows have a so-called “stop,” so the window opening is larger on the inside than on the outside? In that case, I wouldn’t change anything either.
Insulating the window reveal is generally a sensible measure, but it doesn’t directly relate to the energy saving regulation (EnEV); there is no requirement to insulate it. The issue is the thermal bridge at the window reveal, which can actually be mitigated quite well on the inside with a calcium silicate board.
The purpose of this measure is to increase the surface temperature of the reveal to prevent condensation and, consequently, mold.

Yes, we are also wondering why and if the window reveal needs to be insulated at all? It seems unnecessary, right? At least as far as the energy saving regulations are concerned. Only the wall matters for those.
Also, I’m wondering how exactly the 40% allowance for older buildings can be applied? So, if a new build needs to meet a U-value of 0.24, would an older building then only need to meet 0.24 x 1.40 = 0.336? That would mean our 60 cm (24 inches) brick wall with a U-value of 0.366 is almost within the standard range, and we would only need to worry about the other walls.

You have two options: either comply with the energy-saving ordinance values for every modified building component, or meet the overall values of the reference building plus 40%.

The latter becomes difficult if, for example, you only want to renew the roof, because you would very likely also need to upgrade the heating, walls, etc., to achieve the required values for the entire house.
Since you are planning a comprehensive renovation anyway, the 140% rule works in your favor because it allows you to compensate, for example, the (too) poor external wall with better windows, increased roof insulation thickness, or a lower thermal bridge factor.
This works similarly to a KFW efficiency house.