Renovate an old building or build new? Experiences?

Hello everyone,
I am currently facing the decision of purchasing an end-terrace house, built in 1977, 130 sqm for 450k € and renovating it to KfW 70 standard, or buying a semi-detached house, new build, 142 sqm for 630k € from a developer. Both properties are in the same location, 1 km apart. Both have a garage with a parking space, a full basement, and a developed attic.

According to the energy consultant, the renovation would cost about 150k € and include the following:
- Insulation of the exterior facade, basement ceiling, roof (only from the inside)
- New windows and front door
- Underfloor heating (ground floor and upper floor)
- Air heat pump

My question is whether you think this project is feasible with 150k €?

The KfW supports the renovation with a 15% repayment grant and the city of Cologne with another 10%, so a total of 37,500 €, meaning I would only have to repay 112,500 €.
New electrical wiring, new front doors, new bathroom are not yet included, for which I am planning another 20,000 €. Ultimately, the old building with renovation would cost about 590k € + 40k € incidental purchase costs, totaling 630k €, while the new building with some special features would cost 640k € + 50k € incidental purchase costs, thus 690k €. The new building is not a KfW 40 house, but is being built according to the Building Energy Act 2020 and will have an energy certificate A+ with about 23-25 KWh.

The monthly financing results in a difference of about 300 €.

Is it worth renovating with a price difference of about 50k €? Although it would be a full renovation, the walls and roof remain from an old building from 1977, and the garden would also need some beautification.

I can’t decide, maybe you can help me with that.

Thank you and best regards from Cologne

With existing properties, you know what you're getting. New construction can tend to be more expensive.

Plot size? Orientation of living rooms + terrace with regard to cardinal directions? Traffic noise? Road connections, neighbors, floor plan matching needs, ceiling heights ... and so on. I can think of so many criteria, money is rather secondary.

Electricity plus a new bathroom for 20k could already be tight. Had you already included front doors higher up in the 150k? With the old building, there are also surprises that need to be planned for. What about the water pipes?

......with that price difference, the decision for the new build would be easy for me. At least then you have some peace of mind to start with.

I am also in the new build. Hardly any price difference, you have stress with craftsmen both during construction and renovation. However, with the new build, you can design more according to your own taste and then everything is really new (Wasserleitungen, Elektrik Dachstuhl).

A new electrical system, new front doors, new bathroom are not yet factored in, for which I am budgeting another €20,000.

The year 2017 has called and wants its prices back. I also consider the €150k for the KfW70 ambitious. Ventilation is also not yet factored in, but sensible. Like the others, I am in favor of new construction. Especially with a developer, the costs are much easier to estimate than with renovation.