ᐅ KfW financing – is it necessary or not?

Okay, although the topic isn’t really about showing the whole house or comparing energy use against the energy savings from insulation, let’s go with it. So, theoretically, living in a 2m² (22 sq ft) cave would be the most energy-efficient, since it’s small enough for your body heat to provide enough warmth. You’d eat berries and occasionally catch a fish. But surely you don’t mean that seriously; nowadays we live in houses as we do, and our discussions have to be based on that reality.

Now, comparing old buildings to new ones: if a new build uses 5,000 kWh/a heating energy and an undamaged, uninsulated old building consumes 20,000 kWh/a, then the 15,000 kWh/a difference adds up to the 500,000 kWh of embodied energy you mentioned after just over 30 years.

Or calculated over 40 years:
Old building: 0 kWh (existing) + 40 * 20,000 kWh = 800,000 kWh
New build: 500,000 kWh (embodied energy) + 40 * 5,000 kWh = 700,000 kWh

I’m not eager to do the exact math, but the break-even point where the old building surpasses the new build in total energy balance should be around 35 years. So where exactly is the advantage of existing buildings much better now?

*The values of 5,000 kWh for a low-energy new build and 20,000 kWh for an old building come from a quick online search as averages for a 160 m² (1,722 sq ft) house.
*The 500,000 kWh value for the construction of the new build was taken from MayrCh.

Regardless of whether the question was about renovation or new construction: as @nordanney already mentioned, an older building can be renovated to be energy-efficient with significantly less energy input, which changes the cost calculation somewhat.

The fact that subsidies do not make this even more attractive is likely a failure of policy, or perhaps the result of lobbying efforts.

On the other hand, new construction (at least of multi-family buildings) is indeed desired in urban areas with housing shortages. Since these types of buildings are intended to have longer lifespans than those discussed here, I consider it reasonable to build them as energy-efficient as possible.

hampshire schrieb:

No, the house is actually very efficient. We just didn’t build it according to KfW standards – for example, the heating system.

How did you do it then?

Oetti schrieb:

And Super gasoline just comes straight from the ground next to the gas station and therefore produces zero CO2 during production and is better because of that?

If you criticize the environmental costs of battery production, then please include in your calculations the environmental damage caused by crude oil extraction and its transport to the refinery. I mean, oil is well known for practically flowing from the tap, being absolutely clean, and never spilling when "pumped." Then please also calculate that the refining process is very energy-intensive to actually turn crude oil into gasoline. Please also account for what happens to the waste products from production (keyword: heavy fuel oil). Oh yes, and don’t forget the trucking from the refinery to the distributor or gas station. And then also remember that the gasoline is finally burned in the engine.

So, when I look at the entire environmental balance of gasoline—from the point of extraction as crude oil to the moment it is burned in the engine—I honestly don’t find gasoline or heating oil to be any more environmentally friendly than batteries.

Exactly!
It’s always a comprehensive assessment, especially including personal lifestyle. This is the general consensus here.
For example, my parents didn’t even know the word ecology. Back then, they used garden chemicals now mostly banned, lived in basically uninsulated houses heated with oil or wood. This was not that long ago.
And yet, in their overall ecological balance, they achieved results that none of us would even come close to today, nor would we want to.
No car, no travel, vegetables and fruit only from the garden, forest, or neighbors, very little meat—and when they did eat meat, it was self-slaughtered—homemade pasta, and no unnecessary consumption or energy-consuming technology, and so on...
This is not the old cliché “everything was better in the past” because it wasn’t, and I do appreciate innovation, comfortable living, and nice things.
But this generation could truly call themselves super-ecologists in their total balance, given the normal, possible life they had.
When I compare this to our (including my own) current consumption, none of us can really claim to act ecologically, with or without certification.
For this reason, I view all these certificates critically, since the lifestyle common today cannot be ecological at all.
We would have to give up so many conveniences (which I’m reluctant to do), and many simply couldn’t manage that at all.
We should be honest with ourselves about that, with or without KFW or whatever.
The best thing is for each person to start individually...
I welcome every nature-preserving action; for example, I will hardly landscape my property at all and simply leave it as meadow. But I am aware that even the excavator digging the foundation irreversibly damages the ecosystem of this beautiful, large meadow—whether I build a parking lot, playground, or house on it.

Neueshaus2020 schrieb:

Okay, the topic isn’t really about seeing the whole house or comparing energy use to the energy savings from insulation, but alright. So, it would be most energy-efficient to live in a 2m² (22 sq ft) cave, since it's small enough for your body heat to provide sufficient warmth. Then you’d just eat berries and the occasional fish. But you can’t be serious—this is how we live nowadays, and we have to discuss at this level.

Now, comparing old buildings to new ones. If a new building consumes 5,000 kWh/year (annual heating energy) and an uninsulated old building uses 20,000 kWh/year, then the 15,000 kWh/year difference adds up over just 30 years to the 500,000 kWh of embodied energy you mentioned.

Or calculated over 40 years:
Old building: 0 kWh (existing) + 40 * 20,000 kWh = 800,000 kWh
New building: 500,000 kWh ("embodied energy") + 40 * 5,000 kWh = 700,000 kWh

I’m not interested in calculating it exactly, but the breakeven point where the old building surpasses the new one in total energy balance should be around 35 years. So where is the benefit of existing buildings really better?

*The values of 5,000 kWh for a low-energy new build and 20,000 kWh for an old building are averages found in a quick online search for a 160 m² (1,722 sq ft) house.
*The figure of 500,000 kWh for new build construction is taken from MayrCh.

Please really leave out the undertone in the statements; this should be an open discussion.
Of course, saying a 2 m² (22 sq ft) cave and berries as well as body heat as the only heating source is a simplistic dismissal.
But when you then write "this is simply how we live," that could justify or excuse anything. We heat, drive cars, fly on vacation, indulge... that’s how life is today. I don’t agree with considering today’s lifestyle—which I also partly live—as an unchangeable and justifiable right, as you put it. Perhaps the way we live, build homes, drive, and consume really needs to change fundamentally and drastically.
I don’t have a solution, certainly not, but I don’t think it’s appropriate to see our current way of life as justified simply because it’s possible. It’s nice that it’s possible, but if it becomes impossible for ecological reasons, then it just won’t be possible anymore.

Neueshaus2020 schrieb:

All well and good, MayrCh.

But we are not talking about the total energy required for building the house; rather, it’s about the surcharge that insulation or another heating system needs, which reduces energy consumption. The question from the thread starter was clearly whether to go for KfW 55 or not. The question of whether to build a new house at all is not part of this. So your argument completely misses the point.

No, I don’t think so, because @MayrCh’s statement can certainly be included by the questioner in their overall consideration of building new. When I look at the many aspects presented here, I can arrive at a different conclusion regarding KfW than I would without considering those factors.
Therefore, the questioner will decide for themselves whether this is relevant to their decision or “missing the point.” None of us know what is important to them, so we should not dismiss differing contributions. For example, I find the different perspectives interesting, even if I ultimately decide differently.