ᐅ Facade Insulation – Removal of Cladding, External Thermal Insulation Composite Systems (ETICS), and Partial Interior Insulation

Dear community,

I have been reading the forum with great interest for a few weeks now. Thank you for the lively and always very informative discussions.
Now I have some questions where you might be able to help me.

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

The following details about the building fabric (among others according to the construction description) and planned measures:

• Year built: 1964
• Exterior walls ground/floor/attic: hollow block bricks HBL25/50 with 11.5cm (4.5 inches) facing in sand-lime brick
• Condition: in need of renovation with small and larger cracks and peeling paint (expert assumes latex paint), partially painted over by the previous owner; according to the expert and architect these are settlement cracks; see attached photo as an example.
• Basement walls: gravel concrete/heavy concrete/KSV; insulation is not planned since it is a non-living basement
• Insulation: according to the architect/energy consultant, the exterior walls should be insulated with approximately 18cm (7 inches) ETICS insulation; polystyrene insulation is discouraged by him

Also important: The house is a semi-detached and on the north side offset by about 3m (10 feet) to the neighboring house. Insulating this 3m section from the outside is very likely not possible, partly because the insulation would extend onto the neighbor’s property and the neighbor has their terrace roof attached to the house wall. The architect mentioned that interior insulation would be necessary here, presumably with aerated concrete blocks (Ytong).

Now my questions:

• Should the 11.5cm (4.5 inches) facing be removed before insulation, or are preparatory measures recommended (for example, removing latex paint, treating settlement cracks with filler or similar)? One neighbor, for instance, had the facing completely removed before insulating. Our architect advised against removing the facing and said that after cleaning the facade with a high-pressure cleaner, the insulation would just be adhered and mechanically fixed. No further facade preparation would be necessary.
• Is ETICS insulation recommended given the building’s condition? I have read and heard some critical opinions on this.
• How can thermal bridges on the north side be avoided due to the offset? I am concerned that this transition from exterior to interior insulation could cause issues over time.

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

Thank you very much & best regards
Robert

These are very specific questions, so it will probably be difficult to get helpful answers here in a general DIY forum. Especially the question about renewing the facade... that is hard to assess.

Have you consulted a qualified energy consultant for advice? Architects are not necessarily experts in this field. Whether an external thermal insulation composite system (ETICS) is suitable depends, on the one hand, on your goals, and on the other hand, on the overall concept, which should be developed beforehand.

Thank you for your assessment, Tego12! Perhaps a layperson with a similar case and some helpful experience might be found here.

Our energy consultant and architect are the same person. The overall concept for energy efficiency (target KfW70) is already outlined in basic terms (also a requirement for KfW funding), but there is still room for adjustment.

I would say offhand that external thermal insulation composite systems (ETICS) are not necessary.

Hollow-core concrete blocks inherently do not have such a poor U-value. Additionally, the cavity created by the facing brickwork can be economically filled with insulation (under €3,000). This would need to be done anyway if you apply ETICS.
Any further improvement in the U-value through external insulation would be so minimal that it would neither be ecologically, energetically, nor financially justifiable.

If, for whatever reason, you still want to install ETICS, I would recommend keeping the brick veneer facade for soundproofing reasons. According to neighbor law in NRW, you are allowed to extend insulation onto the neighboring property up to the thickness necessary to comply with the energy saving regulations (EnEV). The neighbor must be compensated financially for this (up to the property’s standard land value multiplied by the area built over).

...and even though you didn’t specifically ask: you’re aiming for KfW70 standard. To meet the primary energy requirements for that, you will need either a heat pump, or, in addition to a gas condensing boiler, at least solar thermal and probably a ventilation system as well. What are the specific plans?

Thank you for your feedback, Dr. Hix.

Currently, approximately 18cm (7 inches) of facade insulation, a heat pump, solar thermal system, and decentralized ventilation are planned, at least according to the KfW application. At the moment, there is an oil heating system installed from the year 2000 (burner around 2006). However, full underfloor heating is not planned (among other reasons due to ceiling height and effort), so the heat pump option might still shift towards a gas condensing boiler.