U-value of windows - differences

We have a Uw of ~0.75 ; uf of 1.0 I think, uw of 0.5. Example: Uw goes from 1.05 to 0.75, 200 heating days, 30 sqm windows, average delta to room temperature 13°C -> 39 € per year. If the surcharge is under 1000€, it is economically worthwhile in the long term. (100 assumptions)

does it have something to do with well-being? like radiation cold?

What people consider radiant cold at windows is often drafts... airtight sealing probably wasn't done (always) 20 years ago. In my opinion, you only notice radiant cold if you sit very close to the window - we're not talking about single glazing vs. passive house here.

How many square meters is it? You can very accurately quantify what theoretically can be saved... for example, 0.3 W/m²K would be for 10 m² window area on a crisp winter day with -10°C = 10 m² * 30 K * 0.3 W = 30 W per hour -> 0.660 kWh -> 4.6 cents

Please explain the conversion from W/m² and a temperature difference to a time unit (1 hour) a bit more precisely. In your calculation of 4.6 cents per 10 m² (realistically a bit more for a whole house) and hour, that would mean in winter with 30 days x 24 hours = 33 €/month additional costs. I consider that very very very unlikely. Please provide the correct full formula.

Ok, then it doesn't seem to be worth it. Thanks ☺

The 4.6 cents referred to an entire day - sorry. 0.3 W/ sqm K * 10 sqm * 30 K * 24h = 2160 Wh -> 2.16 kWh -> 1 kWh gas costs ~7 cents -> 15.12 cents (I miscalculated by a factor of 3, as I had a confusion in my head) - but it is correct. 10 sqm of windows is relatively little for a house.. hence the second example -> let it be 30 sqm --> 45.36 cents on this very, very cold winter day (on average -10°C). Now, there aren’t many days like that and the average temperature during the heating months is rather about 6°C between October and April. Let's assume that we don’t heat for the full 240 days, but rather 200 of those and take 7°C average instead of 6°C (somehow I have to account for the solar gains) - then we have, for example, 200 days with a 13°C temperature difference -> 13 °K * 0.3 W/sqmK * 30 sqm * 4800 h = 561 kWh --> 39 € gas per year that could be saved... is surely close to the truth.