Insulation in the 70s compared to today, modern insulation, heating costs

I would be interested in an assessment of how much % more heating costs one has in a house that was solidly built around 1970 according to the standards of that time (including windows), compared to modern insulation as one would typically use today.

Are there very large differences? It concerns exterior walls and the roof.

Where are the greatest losses likely to be? Exterior wall, window, roof?

So which renovations would be especially necessary, which less relevant?

Thank you

No one can really answer that for you. Usually, the actual areas and their values are calculated for that. Then climate data and personal needs are added. So it's too complex for a simple statement.

What kind of wall construction do you have? Insulating the roof is usually relatively easy and already brings quite a bit.

..... Then climate data and individual needs come into play. Too complex, therefore, for a simple statement.

Absolutely correct! Additionally, extra insulation must always be evaluated in conjunction with the system technology. With a water or brine heat pump, one can often avoid excessive insulation measures; with gas condensing boilers, air heat pumps, or wood combustion, somewhat more insulation is usually advisable! However, this must be targeted!!! Usually, an adjustment of the heating system is necessary; otherwise, the "nicely calculated" energy-saving measure dissipates into nothingness.

Best regards

Aha, what does W- or brine heat pump and gas condensing boiler, air heat pump mean? To what extent does the heating system need to be adapted to the insulation?

These are IDE heating types:
Brine heat pump
Air heat pump
Gas condensing boiler

Less heat is required due to the insulation. Therefore, the existing heating system may be oversized and operate inefficiently. The savings effect from the insulation is thus at least partially negated.