Infrared heaters throughout the entire house?

He has nothing against small houses – rather against planning a house (here quite modest in size), with features that one would rather „expect“ in larger houses, meaning because the investment is more worthwhile per area.

No. First, I not only have nothing against small houses, but I even find it actually good when someone does not build beyond their means. And second, it is not about whether the features make sense in terms of equipment level for the size category. I rather point out that the features now addressed here by the OP do not fit the category of house models he is considering. This feature set comes from the world of people who on average are ten years ahead in life, career, and self-reflection compared to the typical builders of the house models in which he is considering installing them. I see the OP starting a family in five years and changing property in another ten years. The potential second-hand buyers will be the same type who are typical builders for these young family models, and they neither seek these features nor want to pay for them. Without corresponding price reductions – as I said, I assume the full write-off of the surcharge – the house would then be a slow seller on the used market. In addition, this feature set is not foreseen in the construction of these highly space-efficient models and will pose accordingly tricky improvisation tasks to the builders (which will in the best case result in drywall oddities). As laudable as it is not to want to strain oneself size-wise with an advanced bachelor pad modeled after a show-off castle, a product of the "space miracle" category still seems unsuitable here as a basic model.

everything that goes out the window is gone, they do not stop the infrared radiation

How do greenhouses work then? (Fifth word)

How do greenhouses work then? (Fünfteswort)

Infrared comes through the glass and heats the materials inside. The heat radiation in the greenhouse warms the air. The warm air can hardly escape because of the glass. Evaporation over the plants generates humidity. Then you have greenhouse climate. If the heat were the heat source in the greenhouse, everything would go out.

I hardly dare to disagree, but with all due respect, I have learned it somewhat differently: Shortwave solar radiation (UV) can pass through glass - longwave infrared radiation that is reflected by the materials inside is much worse (heat through the air is of course even worse). See eyeglass lenses... [ATTACH alt="IMG_20210515_081958.jpg" type="full"]61366[/ATTACH] CR: NASA

Then there is also the hot water issue or legionella risk ...

Another controversially discussed point that is often used against heat pumps. Because here too, planning/misplanning is crucial. Oversized tanks and stagnant water in pipes are the problem regardless of the upstream heat generator. Even a storage temperature beyond 70°C does not help in this case. With that, you only select for the more heat-resistant strains in case of infestation. Apart from that, you would also have to flush all pipes simultaneously with the high storage temperature. But that is not done. With appropriate tank size and sufficient hot water turnover, you have no problem with legionella in your system, whether with gas, pellet heating, or heat pump.

No contradiction. The principle of infrared heating is based on warming materials, not the air. Glass is a poor heat store. Therefore, it is not sensible to hang an infrared heater opposite a window. Your thermal image shows that the glasses did not store any heat. The sun has a very broad radiation spectrum including UV and infrared. You feel UV as sunburn on the skin, infrared as warmth. Ever felt the sun through a window? Window cold, skin warm. Radiation passes through.