Renovating an old building, which insulation measures are mandatory?

Hello everyone, I need your advice because I am not quite clear about the many energy requirements for old houses.

We will start renovating a house from 1930, which has been in the family, at the end of the year. The roof will be completely renewed (woodworm was active) and insulated according to current standards. New windows and roller shutters will also be installed, but only with double glazing, however with an insulation value of 1.0W/(m2K).

We have 60cm thick slate exterior walls, and the facade is in good condition. However, we definitely want to avoid insulating the exterior walls for cost reasons.

Therefore, the only energy-efficient measures planned are the roof and windows. Is that sufficient for the legislator? Or is it mandatory to insulate the exterior walls when buying an old house?

Maybe someone can also tell me approximately how much an energy consultant costs, or do I not necessarily need one? There is no energy certificate.

Thank you very much in advance!

Officially, we had a 450sqm building inspected by an energy consultant and paid around 3 thousand for it. The report was definitely worthwhile because it showed what can be DONE SENSIBLY. I wrote the word xtra big because with expensive building technology, which they like to sell you, you achieve a rather small effect. The result was: Remove all intact mahogany windows, double them up with a strip, equip them with triple glazing, install new seals. Blow Perlite into cavities between the inner wall and the clinker. Repair roof insulation where damaged. End of story. No technology, no solar, nothing. Cost 23 thousand euros. Yield: Oil consumption dropped from 9000l to 6000l per year. The legislator gives you all the freedom with old existing houses. Karsten

The legislator unfortunately gives no freedom at all. Usually, little is adhered to here... Energieeinsparverordnung Anlage3 zum §8: "If you touch the wall, you must insulate it according to Table 1. U=0.24, corresponds to approx. 12 cm required insulation. If you do not touch the wall, you do not have to do anything - but is that sensible?

The insulation of the top floor ceiling or the roof is mandatory within 24 months after purchase. Everything else is optional. The facade insulation prescribed by Lumpi_LE only applies to extensive renovation measures. So, everything is good with you, do it as planned. Something might still come up with the heating system. If it is older than 30 years and not a condensing / low-temperature boiler, it should also be replaced at some point.

Thank you all!

The complete heating system was converted from the former electric heating to an oil central heating system in the year 2000, which will probably remain that way. I might later install a hot water storage tank and lay the corresponding water pipes because the hot water still runs via instantaneous water heaters. Provided that this harmonizes with the existing Viessmann system.

The exterior wall/facade was repainted about 6 years ago and looks quite good, so we will not change anything on the facade and hopefully won’t need to insulate it.

At least we should achieve a better energy rating through the completely new roof including insulation and the new windows with matching roller shutter boxes, and as is well known, this roof insulation is not exactly cheap; it probably accounts for one-third of the total cost of the roof.

I’m curious what prices the roofers will charge; unfortunately, there is hardly any information online about roof prices from people who have renovated an old building.

For us, there are two simple gable roofs (main house and extension) that need to be completely redone including the rafters. One with 144 sqm roof area at a 43-degree pitch and the extension with 83 sqm at a 43-degree pitch. Both roofs will be insulated and will each get 2 normally sized Velux windows.

After roughly adding up individual details found online, I came to a sum of around €55,000, which in our case could make up half of the renovation costs...

Could that be accurate, or is that overestimated? Unfortunately, the contractor companies are taking several weeks to send us the cost estimates. A frustrating situation since the transfer of the house is imminent. Luckily, the purchase price is low.

Regards

For the old roof still has to be removed and disposed of, and someone also has to spend a few minutes on the planning, in my opinion that is set rather low. Roof truss, covering and insulation+sealing are at 250/sqm gross, demolition and disposal ~10-15k€. That makes a total of rather 70k€.