Construction costs are currently skyrocketing

There is a difference between exhaust air without heat recovery and ventilation with heat recovery. In one, the heat stays inside and the moisture goes out, in the other, both go out. And now we can do some calculations. Heating 1 cubic meter of air by 1 degree requires 0.33 Wh. With a temperature difference of 20 degrees and 500 cubic meters of air exchange, 3.3 kWh of heat energy are lost through the exhaust hood. With a recirculation hood and ventilation with 80-90% heat recovery, it's only a fraction of that. In grandma’s uninsulated house from 1965 with 250 kWh/sqm, that doesn’t matter. In new buildings, it does not.

And how do you come up with the 500 cubic meters? I’d have to run it full blast for a whole hour. In reality, full blast runs for a maximum of 10 minutes during a frying process, and even then only for red meat or the famous herrings. With a short pre-run and a somewhat longer post-run. And you have a 20°C difference during cooking times at what percentage of the heating season? Let me be very(!) generous and assume 0.5 kWh heat loss per cooking process during the heating season. In reality, it will be even less, arguments see above. Cooking daily on 120 days per year then makes 60 kWh. I recover half of that alone as waste heat from the stove. The rest is produced in the new building with an annual performance factor of 3. That is, sorry for the expression, a drop in the ocean. People just make good money on recirculation systems.

And how do you come up with the 500cbm?

That was from the 500cbm per hour and because it’s so easy to calculate in your head. It’s clear that you don’t run it at full power for an hour. But the fact remains that a range hood is designed for about 10 air changes per hour, which is quite a lot.

And 20°C difference do you have during cooking times at what % of the heating period?

Not exactly our place of residence, but nearby and at a similar altitude

I have a 20 degree difference on average for 3 months, plus almost as much in March and November. That is probably the entire heating season for us. At the latest from April, the heat pump should only be needed for hot water, probably much earlier.

That was based on the 500 cbm per hour because it’s so easy to calculate mentally. It’s clear that you wouldn’t run it at full power for an entire hour. But the fact remains that a range hood is sized for about 10 air changes per hour, which is quite a lot.


Not exactly our place of residence, but nearby and at a similar altitude

I have an average temperature difference of 20 degrees for 3 months, plus nearly as much in March and November. That is probably our entire heating period. By April at the latest, the heat pump will probably only be needed for hot water, likely even well before then.

Well, then I’ll stick to my numbers, which I already consider very conservative in the sense of being exaggerated. If I convert that to kWh of electricity for the heat pump, it’s peanuts – for that I get a very low-maintenance and affordable range hood that fits my cooking needs (which, as we have seen here, vary greatly).
In a passive house, however, I would actually use recirculation.

Another topic...

Which base plaster? Gypsum or lime? The wet rooms get lime-cement. The price difference between gypsum and a pure lime plaster is €1400.
Exterior wall: filled Poroton MZ70, ventilation system with heat recovery (HRV)

On the base plaster there will be 1mm of fine plaster - price unknown yet.

If you swear by healthy living conditions and absolute mold resistance: lime plaster. Otherwise, regular gypsum plaster will do. If you plan to do the work yourself after plastering and prefer smooth walls, I would reconsider. Because you can achieve that most easily with painter's fleece, but then you don't need to use lime plaster. Lime plaster usually doesn't get 100% smooth, or you have to apply a gypsum filler (often with dispersion) again, and then you might as well skip the lime plaster. There's no doubt that lime plaster is great and has its merits, but it depends on the overall construction whether it is worth it. Personally, I would skip it, especially if controlled ventilation is planned anyway.

If you swear by healthy living and absolute mold resistance: lime plaster. Otherwise, ordinary gypsum plaster will do. If you do the work yourself after plastering and prefer smooth walls, I would reconsider. Because you can most easily get smooth walls with painter's fleece, but then you don't need lime plaster either. Lime plaster is usually not 100% smooth, or you have to add a gypsum filler (often with dispersion) and then you can also skip the lime plaster. No question, lime plaster is great and has its justification, but it depends on the overall construction whether it is worth it. Personally, I would skip it, especially if controlled residential ventilation is planned anyway.

Thanks for the feedback. Yes, indoor climate and health are important to me. But I assume that gypsum is not necessarily harmful to health... I don't want smooth walls. A lime render with a roughcast finish will be applied as the top layer + silicate paint. However, we want to wallpaper the ceilings ourselves with painter's fleece. Can residents notice the difference between gypsum and lime?