KFW 70 is not achieved, target values for gas condensing boilers

I would like to point out that heat and cold protection are very different things. The U-value and temperature profile are not everything. A small example: at e.g. -20℃ outside, the roof surface with good insulation might be about -19℃ cold, and a certain heat flow is flowing out of the house. The roof surface usually does not get significantly colder than the surroundings despite heat radiation. However, if it is +30℃ in summer and the sun is beating down on the roof, one must not assume for heat protection that the roof would be about 30℃ warm - if the roof is now insulated with well insulating material like *wool with low heat storage capacity, the roof will become much warmer than the outside temperature very quickly. This greatly increases the heat difference between inside and outside and despite the low U-value, a lot of heat flows into the house.

That is clear to me and that is exactly what the u-value calculator also tells you.

I point out that heat and cold protection are very different things.....

That is completely correct. In the summer heat period (AT 35°C), exposed roof surfaces can often reach up to 90°C, depending on the absorption rate. Assuming a desired room temperature of 20°C, this results in a temperature difference of 70 K acting as a heating potential!
In the case of the transmission model permitted for the winter load case (heating), however, only 15 K!!!
A significant difference!

Therefore, there are different planning tools for heating load calculation for heating operation and cooling load calculation for summer heat protection!

Regards

Hi, I just wanted to briefly explain what came out for me. So I am not officially making a Kfw 70 house out of it. It would be possible to achieve that through various measures, which are also the reason why most house providers manage KFW 70 even though both the insulation is lower and the heating is somewhat less efficient, therefore not officially. On the one hand, standard values were used in my case, for example e.g. a thermal bridge value of 0.05 W/m²K is added for the walls. If it actually has a value of 0.15 W/m²k, at the end 0.2 W/m²k comes out. That is of course significantly worse. You could avoid that if each thermal bridge is calculated individually, but that is very time-consuming and costs a bit more, about 2500 Euros. House providers do this once for their houses and then sell 20 or more of them and therefore have significantly lower costs in this regard. Another point would be the heating system, which was also calculated with standard values; here you could use the system with its exact manufacturer values which are actually always significantly better, but I was also told that obtaining these manufacturer values is not so easy. And then there are a few other small things like better windows or insulation wool with better U-values, etc. Or a different heating system is used right away, as I originally intended, which in my opinion is not worth it. A wood gasifier was planned, and with that, for the same house I had a calculated consumption of 26 KW/m²a. At least now I roughly know why my house will not be KFW 70. I hope it helps someone a little. Regards

...
Basically, one must distinguish between primary energy verification methods (Energy Saving Ordinance, KfW) and the actual expected real values.
There are various construction projects that have been (are being) artificially improved in the verification. If you look at real practice, KfW 55 quickly becomes just the Energy Saving Ordinance standard!

best regards

What tricks are used to make this artificial improvement?

Thanks in advance
Best regards

With what tricks is this beautifying done?..

For this, "beautifying" would first have to be defined! Intent/ calculation or professional incompetence. There are completely legal (sanctioned) methods aimed solely at the verification procedure, on the other hand illegal, frequently used possibilities that relate to HT´ or qp´´.

v.g.