Offer for Frisian house with garage, okay?

Ok under the circumstances you are right. So the architect is approximately 10,000,-, ground survey 900,-, structural engineering/execution planning and heat certificate together at 4,500,- All fully negotiated offers that only need to be signed.

Solar thermal systems are expensive to purchase. You probably won't make that money back. Especially not if the heat pump runs efficiently. Additionally, a large buffer tank is necessary, which is often misused as a heating buffer. That means the heat pump keeps the large volume of water at temperature constantly. This is uneconomical.