ᐅ EIFS / exterior wall / insulation / energy experts’ experience reports

Hello,

Stefanoi schrieb:
Would it still be possible to explain the advantages/disadvantages of a thicker wall in exchange for less external thermal insulation composite system (ETICS) ..

That is only possible if you want to build purely monolithically; otherwise, you have to include ETICS.

You want to achieve KfW 55, so ETICS must be considered, and based on experience, 24cm (9.5 inches) Poroton blocks and 16cm (6.3 inches) ETICS are necessary. A precise calculation might even show that you need 18cm (7 inches) ETICS; this largely depends on the location of your plot.

If you decide against KfW 55, you do not need ETICS and can build monolithically with a wall thickness of 36.5cm (14.4 inches). The wall thickness depends on the choice of the block (lambda value) but is mainly determined by structural requirements.

Kind regards

Quote from Bauexperte:
"...With these measures, it is possible to build a solid and durable single-family home whose future occupants will not feel like they are living in a technology-heavy plastic shell...."

I understand that this statement is not meant negatively, but we have never regretted our decision for a "technology-heavy plastic shell" (timber frame prefabricated house with external thermal insulation composite system). KFW 70 standard (as Bauexperte rightly noted, meeting KFW 55 would have cost us about €20,000 more), ground-source heat pump, mechanical ventilation with heat recovery. Very comfortable living environment, walls feel "warm" in winter, no issues with moisture – even in the cold climate of Upper Franconia.

Best regards...

Stefanoi schrieb:
...Now I’m just curious about what kind of building envelope one should aim for?
The 24 cm (9.5 inches) plus 16 cm (6.3 inches) exterior insulation system planned for my project feels to me like a bit less masonry and too much insulation.

Taste is very subjective and individual. In my opinion, it is not a reliable guide for a sound decision. Either you pragmatically pursue the goal of cost-effectiveness, or you let yourself be guided by feelings, assumptions, and guesses.
There is no "ultimate" wall construction, only a suitable solution that best fits the individual overall conditions in their entirety.

Stefanoi schrieb:
...Would it still be possible to explain the advantage/disadvantage of a thicker wall with less exterior insulation? ..

Probably worse thermal insulation, better soundproofing.
Kind regards.

Bauexperte schrieb:
Hello,


In conventional home construction, you should expect to spend about 20-25 thousand euros more to build a KfW 55 energy-efficient house. This additional cost comes from thicker masonry, stronger insulation, and a lot more technical equipment. So, as €uro probably suggests, the question arises whether the cost-benefit ratio justifies it.

I have often discussed this with our structural engineer, and we mostly agree that focusing solely on the KfW standard should not be the ultimate measure. If a single-family house is built according to current technology and standards, it is certainly not a bad house; a key point is that the building envelope should meet the values of a KfW 70 energy-efficient house.

The insulation and technology demands coming from Brussels are a tricky matter; after all, those officials don’t have to pay the bill themselves. The lower the target—such as KfW 55—the more money has to be invested. Therefore, it’s not just about the payback of the required funds, but also a personal question: is borrowing at 1 or 2 percentage points lower interest really worth all the technical complexity? Is a house built according to the current Energy Saving Ordinance really worse?

I therefore always recommend our clients adapt the building envelope, including glazing, to meet KfW 70 standards (without external thermal insulation composite systems, ETICS). Renewable technology should be used where possible—preferably a geothermal heat pump; if not, alternatively an air-to-water heat pump; and definitely a ventilation system should be installed. With these measures, a solid and durable single-family home can be realized whose future occupants will not feel like they are living in a technology-heavy plastic shell.

In the coming years, many new technologies will enter the market, ranging from small wind turbines on the roof to battery-storage modules for electricity. Once we reach that point—and if the above recommendations were already considered during construction—then it will be possible to retrofit a fully self-sufficient house. I am confident that at that point, there will be plenty of subsidies available again and—perhaps even more importantly—homeowners’ finances will have recovered from the efforts of today’s new builds.

Best regards

Hello Bauexperte,

Until now, I have been a silent reader in this forum and, of course, a prospective homeowner. Your text literally spoke my mind and dispelled my last doubts about my wall construction and building technology. Especially your last two paragraphs are, in my opinion, an honest and objective assessment of the very confusing topic of energy, building services, and building envelope. I find the hype around Passive House or KfW 55 as the sole forward-looking building approach exaggerated or not always feasible. The middle ground you described above represents for me personally and for my construction project the OPTIMAL SOLUTION, which I had already planned but was unsuccessfully seeking professional confirmation for.

Thanks for that!!!

Kind regards Dudlove

Hello,

Dudlove schrieb:
..I think the hype around Passive House or KfW 55 as the sole future-oriented building standard is exaggerated and not always feasible.

Extremes are rarely truly practical. The real truth usually lies somewhere in between.
It is not difficult to find this balance if you first determine the actual demand (output, energy) for heating, domestic hot water, and ventilation if applicable.
The overall context of the individual building project is always decisive, not isolated details such as the insulation value of a heat recovery ventilation unit.

Best regards

€uro schrieb:
Hello,
extremes approaches are rarely truly sensible. The real truth usually lies somewhere in between.
It is not difficult at all to find this balance if you have first determined the actual demand (performance, energy) for heating, domestic hot water (DHW), and possibly ventilation.
It is always the overall context of the individual construction project that matters, not isolated details like, for example, the insulation value of an exterior wall.

Best regards.

Hello €uro,

what you write is absolutely correct. But I have been reading in various forums about building for quite a while now, and whenever the question arises, "Which type of block should I use? External wall insulation systems (EWIS) or solid/masonry construction? Heating system? Controlled mechanical ventilation... and much more." the typical answer is usually: everything has its pros and cons, or it depends on the specific case. And that is true. The problem is that a future homeowner, who spends their valuable time in such forums looking for information, often has little knowledge of the subject and cannot make much sense of such general answers. Not to mention that they will never truly grasp the overall relationships between the building envelope, technology, economics, ecology, and whatever else. Certainly, many answers or forum posts are technically correct, but a person seeking help (without expertise) rarely finds anything useful in them.

This is not a criticism; I think this forum is great and I have already learned a lot for my own benefit. But I found Bauexperte’s post excellent: simple, honest (at least that’s how it feels to me), and it clearly outlined a great middle ground. And what’s more, it matches exactly how I want to approach my own building project.

Best regards, Dudlove