Sandstone - KO criterion or isolatable?

The topic is probably more complex than you currently see.

Until last year, I owned a very old house, some of whose exterior walls consisted of [Baumberger Sandstein]. However, the walls were significantly older than yours, about 270 years old. In addition, they were mostly additionally insulated with a brick wall placed inside (if you want to call that insulation at all), making them up to about 1m thick :cool:

Insulating from the inside is usually bad (worse than outside for sure). For this reason, I partially installed a curtain facade on the building made of 10cm stone wool + larch cladding.

I suspect the planned building is in a rural area? (Barns usually are) Different rules apply there (building authority!), so you should definitely ask in advance what is allowed. That could mean a bigger restriction than you might imagine :-8

Yes, one should indeed calculate that, because it is absolute nonsense. According to the rule of thumb, 15,000 kWh/year is achieved with a 15 kWp system. But the system unfortunately produces 75% of the energy at times when it is not needed for the heat pump and feeds it into the grid for 8 or 9 cents. You generate just under 4,000 kWh of electricity yourself in winter.

On the other hand, besides the heat pump, there are investment costs of easily 15,000 to 20,000 EUR for 15 kWp, financed at currently 5-6% private loan interest.

6,000 kWh heating electricity at 25 cents/kWh costs 1,500 EUR. You can calculate for yourself when you have paid off your photovoltaic investment, including interest. 15 years easily go by.

Get well soon ;)

Photovoltaics can be excellently combined with air conditioning for the summer :)

I don't want to say anything, but natural sandstone masonry in a building from 1960? Plastered on the outside? Who does that.

I don't believe you have natural sandstone walls. That would be completely unusual. And plastering or insulating a natural sandstone facade I would call the biggest building sin.

I suspect you are confusing something.

Thank you for your feedback so far. The real estate agent confirmed again that it is natural sandstone (I explicitly asked again whether it is natural sandstone or limestone sandstone). I'm no longer quite sure about the plastering, whether I'm confusing a word here, but inside you can only see the sandstone on one wall, the rest is covered with something (white inside, yellow outside). Understood, so possibly "live with the additional costs" and hope that nothing triples here in the near future.

For your information regarding the costs of an ETICS: This year we paid €140 per m2 net for a gable wall with one window including plastering and painting. However, it could have been significantly more expensive (up to €230)... Additionally, there was scaffolding for 6 weeks (€1,300 net) and extending the roof overhang (€5,000 net). Prices are from Cologne!

The broker had confirmed to me again natural sandstone (I had explicitly also asked again whether it was natural or lime sandstone).

Again, I consider it impossible that it is natural sandstone. Please post a photo. I am really interested in this now.

Or is your house from 1860? Then it would still be somehow conceivable.