Too many windows for the Energy Saving Ordinance 2016

Hello everyone,

my architect called me today and said he can’t meet the energy value for the Energy Saving Ordinance 2016, we might have to make fewer windows or redesign something, add more insulation....
By now I feel like this architect has no idea what he’s doing, he has already made mistakes with the drawings and couldn’t handle his software properly....
The plan is a small bungalow with a 35° roof that can be expanded if necessary.
The wall is planned with 17.5 cm Poroton, 12 cm insulation, 11.5 cm clinker. Now he says the energy value is far from the target value, we might have to use wooden windows, fewer windows bla bla bla... ?!?!?!?
That’s not normal yet, he’s doing something wrong, isn’t he? In the north I haven’t planned a single window!
I urgently need your professional knowledge!!!
Attached is the floor plan of my ground floor (the bottom is south)
Regards Christian

My opinion, there are too many windows, many of which are also very large or even floor-to-ceiling. The wall would need 24 cm Ytong plus insulation plus clinker.

Ultimately, you have to calculate that. But aiming directly for wood windows is exaggerated. Passive house standards can be achieved with plastic windows. Making the stone thicker would also be a waste of money. Thicker insulation would be effective and efficient.

Dear Ilalei, please quickly forget what Nordlys wrote. Neither are there too many windows, nor are they too large, nor is there anything wrong with floor-to-ceiling ones. Also, the wall construction with aerated concrete plus insulation is worse than your previous one, and the brick veneer doesn’t help you with your problem either. Five mistakes in two sentences. Respect!

First of all, regarding windows in general, the weak points are the frames and the component interfaces. The larger the window, the smaller the percentage share of frames and interfaces.

You could easily extend your 17.5 cm wall by 2 or 4 cm of insulation. No reason to switch to aerated concrete. Aerated concrete is the building material for monolithic buildings. Using it with insulation makes no sense.

Now to the most important point, the Energy Saving Ordinance compares your building with an exactly identical building with standard components. If you have 100 windows, your Energy Saving Ordinance comparison building also has 100 windows.

So there is quite a bit of evidence that your architect has no idea. The number of windows factor cancels out if you did not have the idea of installing simply glazed box windows.

I find my mistakes correct. We have a similarly sized bungalow (108 sqm living space) also with a 35-degree roof. It has fewer windows, only one floor-to-ceiling element, it has 30 cm Ytong plastered, it has zero extra insulation, gas and solar, no controlled residential ventilation, nothing, it easily meets the energy saving ordinance and is not far from KFW 55.

Window is not just window. Nordlys yours may have a better U-value.

I would inquire about the additional cost for plastic windows with a better U-value. Plastic windows are available in the passive house standard and wooden windows do not necessarily mean a better U-value.