ᐅ How to Achieve KfW40 Standard? Energy Systems and Cost Efficiency

As mentioned, it’s all a matter of calculations. You can also choose a different insulating brick with significantly better values. In the end, it’s about doing the math. However, don’t forget the comfort factor, as KFW standards are not a guarantee for comfort. Upgrading will always incur some costs—it’s just a question of where it fits best and has the most impact.

pagoni2020 schrieb:

As mentioned, it’s all a matter of calculation.

This applies to the general contractor (GC). They build using “their” brick, “their” insulation, and their options.
Therefore, you should inform the GC about the KfW40 requirement so that THEY can implement it. If a GC generally builds with Poroton, they won’t touch Ytong.
This reply is not directed at you @pagoni2020 but at the original poster.

@ypg: Yes, you’re right, and that’s exactly how we’ll do it.

I’m familiar with many homes built by the general contractor, and they all offer good value for money, with excellent support. But of course, these are budget builds.

Typically, these are KfW 55-standard houses made of aerated concrete, with external thermal insulation composite systems (ETICS), ground source heat pumps from Tecalor, and deep boreholes. There’s little turnover among the tradespeople—always the same two or three site managers (which is good). Materials are affordable and acceptable but nothing extraordinary outside the mainstream. Changing insulation panels or the entire ETICS finish, for example, is unlikely. It’s standard off-the-shelf design, not haute couture.

I’m pretty sure that in the end, it will be the homeowners who decide to add a photovoltaic system later on. KfW 40 or KfW 40+ standards will probably be rare in his projects as well.

In this respect, I’m particularly interested in your opinions on the size, orientation, and economic viability of a photovoltaic system on a 30-degree gable roof with an east-west orientation. Although economic viability isn’t everything. We would also like to have a climate-friendly and future-proof feeling about the whole energy technology setup. Especially since my wife has been dedicated to saving the world for several years now, and I do my best to help along. ;-)

We’re building here for my parents, so we need to keep an eye on the budget. However, we definitely want to build in a way that the house could eventually become a possible retirement home for us. We would then sell our current home.

We’ll definitely bring in an energy consultant at some point. I’m just the type who likes to gather some knowledge first so that the tradespeople’s advice doesn’t sound like gibberish to me. So, thanks again to everyone for the advice—and maybe more will come...

Wishing you all a Happy New Year in advance!

If your wife (and you) want to save the world, then buy an existing property.
Building a new house, especially a single-family home, is not the ecological way to go 😉
I follow @ypg build just like your general contractor always does. That’s the most likely way to succeed.

That sounds reasonable, as having a reliable general contractor (GC) is already half the battle and saves you a lot of trouble and energy 😀!!!

Regarding photovoltaics, there is a forum you can easily find on Google. In my opinion, they mostly speak “in another language” there... fortunately, it’s a bit more straightforward here, which suits a simple character like me.

A photovoltaic provider has already been mentioned to you earlier in this forum. If you also include the GC’s electrician, that would be a good start. In our case, the electrician working for the GC made a very good offer, and we will likely accept it because everything comes from one source. It might be a few dollars cheaper elsewhere, but having everything from one source is more important to me.

In the other forum, the general opinion is that photovoltaics always pay off and should be installed as large as possible, even more than the 9.8 kWp if possible. Ultimately, there is no one-size-fits-all calculation; we will achieve KfW40Plus standard, but only because we wanted a high insulation standard anyway. We will need to install a battery storage system regardless, which we will almost get paid for through the feed-in premium.

As has been pointed out here sometimes, you can justify many things with storage systems. Regarding the panels, there are thousands of opinions: some offer longer warranties, others higher efficiency, and others better prices... For me, reliable installation is very important too. It’s like with cars—there are valid reasons for everything from Dacia to Lexus.

In our case, it will probably be Solarwatt panels with a 30-year warranty and glass modules, because the electrician sells and knows them, and they are supposed to be good. But the other providers certainly have their advantages as well.

In your case, it might be difficult to build a budget house now for the parents, which they will later live in as a desired KfW-xy energy-efficient house.

Just based on feeling, I would consider building the parents’ house now to the current energy standard without specific KfW measures. That way, you already have a really good house, and the parents probably use very little energy anyway, so they are naturally frugal when it comes to consumption. If you ever want to live in it later... who knows what life will bring, then you could implement the appropriate and currently feasible measures, whether photovoltaics or something else. Until then, what is considered state-of-the-art today will already be outdated.

The phrase "saving the world" referred to energy technology and was not meant entirely seriously. I just wanted to express that the economic aspect is not everything. You also need to have a good understanding of the technology.

Existing buildings are almost as rare here as plots of land. So: a nice dream...