ᐅ General Questions About Insulation

Hello forum community,

some of you might shake your heads in disbelief, but I have to ask a few beginner questions. Maybe they have already been answered, but during my quick browse today I couldn’t find anything on these topics. So here are my questions:

We want to build a house, as the topic suggests. Of course, it will be an energy-efficient or passive house. There are classifications like KfW 70, 55, 40 (energy efficiency standards). Naturally, we want to keep costs within a reasonable budget. I am interested in the required insulation values for each of these categories. Since thicker insulation means more weight, a prefabricated house might eventually be ruled out. Currently, I am looking at a solid construction house with walls using Duo Therm insulation but I am not fixed on that. A 30cm (12 inch) wall has a U-value of 0.21 W/m²K. How does that compare to the U-value of triple-glazed windows? And what about the corresponding roof insulation? A table with these values would be helpful. Who actually defines the classifications? Or is it all determined with the blower door test?

The rest is probably standard: solar panels on the roof, likely an air-to-water heat pump, underfloor heating, and of course, a mechanical ventilation system with heat recovery to prevent mold. Perhaps you can understand and expand on my basic considerations? I want to avoid compensating for poor insulation with a larger heating system, but on the other hand, I don’t want to overspend on insulation either...

Best regards,
Axel

Almost 150 posts and no personal opinion? What’s the reason? Too many questions or the wrong forum?

Since thicker insulation naturally means more weight, prefab houses eventually become impossible.

Explain this causality...

Certainly, when the material thickness increases, the component’s weight also goes up... but I have never seen "weight" used as a deciding factor in house construction. Where do you plan to build? On a houseboat?

DuoTherm... that didn’t ring a bell for me either. A quick search... ah, Lego bricks.

I am interested in the required insulation values for the different classifications.

These are derived from the respective terms. Each corresponds to xx% of the primary energy demand Qp of the respective reference building (plus a slightly higher transmission heat loss Ht).
Take a look at the Wikipedia article on "Energy standard."
In my opinion, the insulation values for individual components are not capped at fixed maximums; rather, a balanced result from all components must reach the Ht value.
Heating technology then comes into play in combination with the primary energy consumption.

And, of course, controlled ventilation to prevent mold.

A controlled ventilation system is neither for nor against mold. A ventilation unit in your house primarily ensures the minimum air exchange rate required by standards. Besides that, it’s quite a luxury.

Regarding the U-values you mentioned for comparing requirements of different KfW standards, I would gladly share an official article... but since linking isn’t allowed here, I’ll send it via private message.

Regards,
Kalksandstein

Hello Axel,

Seneca schrieb:

Probably some will shake their heads in disgust, but I have to ask a few beginner questions.

Wrong adjective...

Seneca schrieb:

Maybe they have already been answered, but in my brief scan today I didn't find anything on this.

... that fits better; a "brief scan" is simply not enough. Also, you write without punctuation ... it’s quite hard to read.

Seneca schrieb:

As here, we want to build a house. Of course, an energy-saving house or efficiency house. There are classifications like KFW 70, 55, 40. Naturally, it should all stay within budget... I am currently interested in a solid masonry house with Duo Therm walls.

So a "Lego house," as my predecessor called it, or a "squeaky house," as I call it.

From these first sentences, it’s clear that you have little to no understanding of what you are about to undertake; an extremely bad starting point for building a house...!

Seneca schrieb:

Perhaps you can understand and expand on my basic considerations? I don’t want to compensate for poor insulation with a bigger heating system, nor do I want to spend too much on insulation...

Here we are back to the "brief scan." Many users on this forum have taken great care to share their experiences. Click through the various subforums and gradually educate yourself step by step as you approach building your house.

It is not enough to be simply driven by the desire to build a house and to do it as cheaply as possible. By the way, a forum like this cannot fill knowledge gaps 100%; it can only provide guidance on how to get help. From what I read, your first step should be to hire professional help (also during the build as construction supervision). Then, the basics and connections within the valid energy-saving regulations will become clear.

Best regards

Hello Saneca,

like the two previous posters, I can only recommend that you start working on this thoroughly and early. Read forums, visit trade fairs, go to model home parks, and talk to people from construction companies, banks, and suppliers of individual trades. You will find that when you speak with 10 people, you get 20 opinions, but with every conversation, you become a bit wiser and new questions arise. I also strongly recommend finding an independent construction supervisor.

And definitely don’t be misled by any internet prices. For some trades, you can manage with the standard option, but for many, you want a bit more. Yesterday we went through the sample rooms in advance, and you start wanting this and that as well. On top of that, there are many additional costs not included in the construction and service specifications, such as typical ancillary building costs and much more.

So, building expert, I find it a bit unfair to simply dismiss my questions just because you don’t like my German or my punctuation. And you’re even a moderator here? You should set an example, not just complain. Then the usual advice about the three Rs (Read, read, and read). Why don’t you address my questions first like Karliseppel did, and then you can criticize my German.

Now to the topic. I admit that I don’t know much about house building compared to you. That’s actually why I was thinking about a prefabricated house. And that’s why I’m here. However, I didn’t realize this was such an exclusive group where questions don’t even get answered. Anyway, thanks to Karliseppel for the link in the private message; that gave me something to read and will help me avoid more beginner questions in the future. (But I thought that’s what forums were for?)

Best regards, Axel