How to move from KfW55 to KfW40+?

Construction expert, one more question (because I'm interested). The 55 has different values....

You mean: HT doesn't play a role and I might be able to lower Q_p enough with the solar system + buffer?

Because the 40 Plus has a different HT value, which is not influenced by the photovoltaic system.

Best regards, Thorsten

But Ht plays a significant role. More precisely, I even believe that Qp with heat pump (thanks to the political primary energy factor) and controlled residential ventilation is already met, but Ht is probably the critical point and that is where it becomes extremely difficult with monolithic construction.

Normally, the wall should have a U-value of 0.15 and that requires either a T7 or the corresponding aerated concrete block with a lambda of 0.07. A 0.08 with 49cm achieves 0.16 – meaning that other components would have to overcompensate for that, which unfortunately is difficult because these are also weighted down by factors, for example the roof with a calculated KFW40 U-value of 0.11 already offers hardly any savings potential.

I have calculated back and forth, and meanwhile I think that with monolithic construction, KFW55 is just still economically feasible to realize and then according to reference values according to the technical data sheet because the flat WB approach already ruins everything. The required 0.035 for the WB surcharge can also be simply demonstrated WITHOUT exact WB calculation using Form D (KFW thermal bridge short method). All valid from 01.04.2016.

Calculations:

U-value Energy Saving Ordinance 2016: 0.28
KFW 55: 0.28 x 0.70 = 0.196; 0.20 according to reference values
KFW40: 0.28 x 0.55 = 0.154; worse values here must be overcompensated elsewhere

WB surcharge KFW40: 0.05 x 0.55 = 0.0275; In my opinion this is achievable with monolithic construction; The locally based brick manufacturer advertises 0.025 with exact calculation

, a very valuable contribution in my personal perception.

I don’t fully understand the topic yet. I’m currently considering whether I could get my Kfw70 (which has better values, somewhere between 70 and 55) down to KFW55 with photovoltaics + buffer (long-term value of the house). Now: Most likely no, that little bit of auxiliary energy just doesn’t make up for it. "Politically declining PEV of electricity" notwithstanding. I could achieve Q_p, but not the rest anymore (unless I redo the insulation, make the floor slab thicker + insulate, ...). I can forget it; the substance as it is built is, in hindsight, hard to positively influence towards KfW criteria, I believe.

Most people don’t immediately realize that this whole primary energy calculation according to KFW depends on many factors (including those mentioned above), but also on the "type of fuel" of the heating system.

What, in my personal perception, is very relevant for the people living in the house: The annual heating energy demand (energy carrier) = annual costs. The primary energy demand is a derived, calculated (partly quasi-statically defined) value, usually depending on the energy carrier ... (and its future price development).

Certainly, you can invest in the KFW class, which does not pay off in this respect, but makes ecological sense and is fun. You have to be able to afford that. Here too, the calculation is not quite so simple ... when do I invest in ecology, not in my personal business case?

Nevertheless, the topic of energy and living is fascinating and beautiful as well as exciting for me.

Best regards, Thorsten

Good evening Thorsten,

Building expert, one more question (because I am interested). The 55 model has different values....

You mean: HT doesn’t play a role and I might be able to get Q_p low enough with the solar system + buffer?

Because the 40 Plus has a different HT value, which isn’t influenced by the photovoltaic system

Honestly? I’m not interested in these number games, that’s probably why I don’t keep track of them and could only give you half-baked answers; which I of course won’t do. If one of our interested parties wishes to go into detail on this, the relevant expert will join at the next appointment.

I know someone who knows about this; that’s all that matters to me

Rhenish greetings

Good evening,

this is the matter of experts and laymen.

Normally, the wall should have a U-value of 0.15, and for that, a T7 or the corresponding aerated concrete block with a lambda of 0.07 is required.

Aerated concrete is best suited because, due to its uniform porosity, it has uniform thermal conductivity and a high heat storage capacity. It ensures a high airtightness of the building envelope, thereby avoiding corresponding energy losses.

I have calculated back and forth, and meanwhile, I think that with monolithic construction, KFW55 is just still economically feasible.

Anything from KFW 55 onwards certainly raises the legitimate question of amortization. However, it is completely irrelevant whether construction is to be done to KFW 55 standards using ETICS or monolithic construction. The additional costs for both construction methods are almost identical.

There have been passive houses with monolithic construction using 36.5 cm stones for years; even as multi-storey apartment buildings. By the way, anyone building a multi-family house as a capital investment primarily decides based on the yield calculation available to them; it can therefore hardly be as uneconomical for the builders as you are currently trying to portray. That a good part is owed to green conscience as well as political will goes without saying.

Ask Aunt Google if you don’t want to believe me

Rhineland regards

That means a photovoltaic system with battery storage might possibly be sufficient to reach KfW 40+?
Then with a €15,000 subsidy, not much of an additional cost would be necessary.

Best regards,
dsin8788

What is meant by that or what is behind it?