ᐅ Renovating an Old Roof or Upgrading Interior Insulation? A Guide for Homes Built Around 1920

Dear Forum,

We are planning to buy a semi-detached house built around 1920 with an extension from the 1960s.
Below are a few drawings/pictures related to the roof:

From an energy perspective, I want to invest something and will have an individual building energy assessment (iSFP) done.
Our budget is limited, otherwise we would probably do everything.
My thoughts:
- Roof: Either renew insulation between rafters plus internal insulation, or completely renovate the roof after, for example, 4–5 years (see another forum post).

Current rough estimates for a full roof renovation are about 70,000€ (which is not really within our budget).
I will soon visit a carpenter to assess various things.
I fear the evaluation might say something like:
“Your planned internal insulation can be done, but due to the complexity it won’t achieve the insulation effect you want...”

Others say the tiles still look good and the "Biberschwanz" tiles (beaver tail tiles) can last a very long time. Unfortunately, I don’t know how old the current tiles are.
Also, some years ago, insulation of the attic and probably the sloped ceiling on the second floor was done with about 15–20cm (6–8 inches) of glass wool (?).

What do you think?
Is it worth investing in renewing only the internal insulation (< 15,000€), leave the rest as is, or is it better to tackle the whole roof eventually?
In this context, would you remove the ceiling between the attic and the second floor to make internal insulation easier and gain ceiling height (+1.5m (5 ft)), or would the thermal disadvantages be higher with just renewed internal insulation?

Thank you and best regards,
Sebastian

SebastianHe schrieb:

We are going to buy a semi-detached house built in 1920 with an extension from the 1960s.
Below are a few drawings/images related to the roof:

The details are hard to see (and even harder to recognize) in these thumbnail collages.

---

https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/

The entirely new roof with continuous insulation above the rafters is obviously better, as you can build everything according to current standards at once.
I don’t understand why the EL option should cost 15k.
Study the necessary technical knowledge, double up the rafters, add mass to the roof, and go for it.

Yes, that works, thanks. That is the maximum budget I want to allocate for this. I am currently trying to estimate what the different measures might cost me. I think 15,000 (fifteen thousand) will be quite generous with a lot of personal effort, but if most of the work is outsourced, it might not be too much.

Here are a few pictures in better quality:

- The roof has an area of about 120m² (1,290 sq ft).