Ecologically built house with wooden facade - Features

Don't annoy the seller with too many technical questions. He didn't build with technical datasheets, but eco-friendly and beautiful, and did many things deliberately differently. Show him that you appreciate the house and have been searching for it for a long time. Other potential buyers are already asking him too much about COP, kWh, and other things that are unimportant to him.

If the air-water heat pump does not work so well with the existing radiators, they can be replaced later. A missing installation level should also not be a big issue. It worked for 30 years without it. And the fact that Fermacell was used instead of drywall speaks, along with the ventilated facade, for a look at higher-quality construction. If location and spaceangebot fit, that should determine the decision.

Thank you very much for the many positive comments, by now I also think that you can’t go wrong with the house. Besides, before buying, we would anyway have the building surveyor take a look at it. Now we just have to wait until the sellers decide, I will get back to you as soon as there is news! Best regards, Hausbaufaehig

If the air-water heat pump doesn't work so well with the existing radiators, you can still replace them later.

but it would be pretty stupid if FIRST the seller tears out and replaces the functioning heating system from the house that was probably well thought out 25 years ago

The purchase price already includes the new heating system including installation.

instead of canceling and reducing the price accordingly ... ... and then after one winter of freezing INVEST AGAIN in the heating system Aren't quickly €10,000 or more burned in such a "two-stage" procedure?

In this range, a heat pump works almost like an immersion heater – energy goes 1:1 into the heating. The question is rather whether 35-40 degrees are sufficient. As a maximum. 50 is a deal-breaker for an (efficient) heat pump.

That is wrong. Up to 55° flow temperature, a heat pump loses less than 20% efficiency compared to 35° flow temperature. Above that, it slowly gets expensive. STILL, of course you should make sure to get down as far as possible. The first measure is to ALWAYS turn ALL radiators fully up and lower the flow temperature until it gets too cold somewhere. Only then slightly throttle the radiators in the too warm areas (not on the thermostat head!). And of course no night setback. That the new heat pump should be able to do 70° speaks for a modern heat pump with R290 as refrigerant. That’s already half the battle, those things really run well. Another maximally large photovoltaic system on the roof, eventually new windows, then it will work out.

I am happy to give my two cents here. The wall construction is absolutely fine for the year of construction and is still mostly done that way today. 60x160mm frames with mineral wool or cellulose blown insulation are still standard today; alternatively, you can also use wood fiberboards. The ventilated facade with board/cover cladding is also still common today, but that is just a matter of personal preference. There are various options. If the Douglas fir is untreated, it will have already turned gray. If you like the silver-gray coloration, you don't need to maintain it any further and can leave it as is.

The only thing that is done differently today is the installation layer (about 6 cm), which is additionally insulated with wood fiber or stone wool. Usually, an OSB board is screwed onto the frame from the inside as an airtight bonded layer (= vapor barrier), and the installation layer is applied there.

If you don't have underfloor heating, I would ask the seller if he would leave out the air-to-water heat pump and let you have the house with an oil heating system for a lower price. For a house like this, you could also consider a pellet heating system (which often fits into the old boiler room with oil tanks and offers 45-50% subsidy when replacing an oil heating system) or possibly even install a soapstone/wood-burning stove additionally on the ground floor; that fits perfectly with the concept of the house.

I recommend the YouTube channel of the carpentry Meik Ehrath on the subject of wood/frame construction, where you will find all the essential information on the topic.