Facade insulation - Removing cladding, ETICS & partially interior insulation

Dear community,

I have been reading this forum with great interest for a few weeks now. Many thanks for the lively exchange, always very informative. Now I have questions that you might be able to help me with.

But first some context: We are planning a renovation of the exterior facade, including insulation & plaster on our newly purchased single-family house (semi-detached house).

The following information about the substance (among others according to building description) & planned measures:

[*]Year of construction: 1964
[*]Exterior walls ground floor/upper floor/attic: hollow blocks HBL25/50 with 11.5 cm facing in sand-lime brick
[*]Condition: in need of renovation with smaller/larger cracks and peeling paint (expert assumes latex paint), partially locally painted over by previous owner; according to expert and architect these are settlement cracks; see attached photo as example.
[*]Basement walls: gravel concrete/heavy concrete/KSV; should not be insulated as there is no living basement
[*]Insulation: according to architect/energy consultant the exterior walls should be insulated with approx. 18 cm ETICS insulation; he advises against polystyrene

Also important: The house is a semi-detached house and is set back by approx. 3 m on the north side to the neighboring house. On these 3 m it is very likely not possible to insulate from the outside, among other things because the insulation would extend into the neighbor's property and the neighbor has mounted his terrace roof on the house wall. The architect referred here to a necessary interior insulation, probably with Ytong.

Now my questions:

[*]Should the 11.5 cm facing be removed before insulation or are preparatory measures recommended (e.g., removing latex paint, treating settlement cracks by filling or similar)? A neighbor had the facing completely removed before insulation. Our architect advised against removing the facing and said the insulation will be glued/doweled on after cleaning the facade with a high-pressure cleaner. No further preparation of the facade would be necessary.
[*]Is ETICS insulation recommended for this substance? I have already heard and read several critical opinions.
[*]How can thermal bridges on the north side due to the offset be avoided? I fear that this change from exterior to interior insulation will cause problems in the medium term.

I hope you have all the information to answer the questions.

Many thanks & best regards
Robert

These are such specific questions for me that you will probably have a hard time getting helpful answers here in a "layperson forum." Especially the question about renewing the facade... hardly assessable.

Have you ever asked a competent energy consultant for information? Architects are not necessarily experts in this field. Whether an ETICS insulation makes sense or not depends, on the one hand, on your goals with it and, on the other hand, on the overall concept, which should be created in advance.

Thank you for your assessment, Tego12! Perhaps a layperson with a similar case and helpful experience will be found here. Energy consultant & architect are the same person for us. The overall concept for energy efficiency (goal KfW70) is already outlined in basic terms (also as a prerequisite for KFW funding), but there is still room for maneuver.

I would spontaneously claim that an ETICS is not necessary.

Hollow concrete blocks per se do not have such a bad U-value. Additionally, there is the cavity due to the facing shell, which can be inexpensively blown out (<3,000€). This would have to be done anyway if you install an ETICS.
The further improvement of the U-value through external insulation is then so minimal that it would be neither ecologically, nor energetically, nor financially sensible.

If you, for whatever reasons, still want to have an ETICS installed, I would keep the facing facade for soundproofing reasons. The neighbor law in NRW allows you to overshoot insulation onto the neighbor’s property up to an insulation thickness required to comply with the energy saving ordinance. The neighbor would have to be financially compensated for this (maximum land value * built-up area).

...and even if that was not specifically asked: you are aiming for KFW70. In order to achieve that in terms of primary energy, you either need a heat pump, or in addition to the gas condensing boiler at least solar thermal and probably also a ventilation system. What is specifically planned?

Thank you for your feedback, Dr Hix.

Currently, approximately 18cm of facade insulation, a heat pump, solar thermal energy, and decentralized ventilation are planned, at least according to the [KfW application]. Currently, an oil heating system from the year 2000 (burner ~2006) is installed. However, comprehensive underfloor heating is not planned (among other things due to room height & effort), so the heat pump could possibly shift towards a gas condensing boiler.