Shell basement/foundation has stood for 10 years

Tough weekend. Cisterns are installed. Floor construction with underfloor heating in the bungalow is finished. In the basement, we're behind. A lot of stuff from the technical room had to be stored in such a way that it bothers the screed installer as little as possible but doesn't have to be moved around constantly..: For example the hanging cables ;-) The crane truck that was supposed to deliver and install the cisterns didn't come exactly where they were supposed to, so we quickly included the excavator in the alignment process. Every one is 10,000 liters and 6.5 tons heavy. Having the right tools is key :) In the photos, you can see the round arch in the foundation on which a (castle) tower of the original building was supposed to be constructed. The whole thing is 3m deep and solidly concreted. That doesn’t make things easier for us. I will probably rent a hydraulic hammer for the excavator to solve the problem.

cool project. We also built an infinity pool on the slope. How big is it supposed to be? I fear the heating system is very undersized. With an overflow pool, the heat loss is greater. If you want to heat the pool even at cool temperatures, try to achieve the heating capacity at least 3/4, preferably 1 to 1. 9kw is nothing. The optimal solution would be to heat the pool with the gas heater and heat exchanger. In summer, maintain it with a heat pump (because even there the 9kw will not be enough). A pool loses up to 2-3 degrees at night depending on location, temperature, cover, insulation. To raise 1m3 of water by 1°C you need 1.16 kW power. Let's say the pool is small and has 20m3. Heating by one degree thus requires 23.2 kWh. To compensate a night loss of 3 degrees means 69.6 kWh. That means you need almost 8 hours to compensate the night loss. Losses in transmission etc. are not even considered yet. A real heating is thus not possible. Especially not with a larger pool. So either connect a (large) heat pump or fire it with the gas boiler. Please remember that an infinity pool requires a compensation/surge tank and also check valves. The pump is not a pool pump?! If you need more input regarding the pool, feel free to ask.

Good morning, thanks for the offer, I will gladly get back to it! I know your project as a silent reader - impressive. My resources are just a bit smaller than intended to use :-) That makes our project very ambitious. Gas has become difficult. The technical room doesn’t have a millimeter of unused space. My heating engineer has already dealt with it more than I can explain here. As soon as we have screed in and a bit of space, we will deal with the pool. We are actually working somewhat in parallel. We have 12 years of old building renovation behind us, bit by bit, so we definitely don’t want to have another years-long construction site. That’s why we are doing the whole thing at once now. Besides the fact that the excavator ties up 25,000 euros of capital which I definitely don’t see as reasonable in the long run ;-) My bricklayer has already helped build large indoor pools and big spas, so from that side we are relatively well off. It will be a foil pool, my roofer can weld the foil and as mentioned my heating engineer privately deals with pool technology and has already thought quite a bit about it. An IBC container is planned as an overflow tank. If necessary, we might also bring in a friend of my bricklayer who has been building pools for about 15 years. The more input the better. This is not a small thing. And as for the planned size, we’re rather at about 70..80 m³ with shallow zone. That’s the plain theory for now :-) The garden side with the large window fronts is basically supposed to be walled up at the property boundary and facing the park area (street side has little traffic but many hikers, cyclists) and the whole area is supposed to become a "wellness oasis." Terrace, pool, whirlpool, outdoor shower and lounge area ;-) To the north we still have 800 square meters of building land towards the forest which we probably want to provide to a local animal protection association for planting. We don’t have a green thumb nor much fun with gardening. We’ll see how that goes. Since yesterday there has definitely been a huge amount of excavated earth. Today is another hard working day, next week filling the heating and hopefully from 16.3. screed goes in :-) Indian proverb: How do you eat an elephant? Piece by piece ;-)

For 70-80m3 you should have more than 40kw heating capacity. Will the IBC then be placed outside? With the surplus electrical energy from the roof, I would consider whether a heat pump could be installed. In any case, provide the pipes and bypass for it right away. Please keep me updated.

Wouldn't solar thermal energy be a good idea as an exception for such a heat demand?

If you have enough surface area, yes. But it only works in summer. The absorber area should correspond to the surface area of the pool. Then you can also heat a bit during bad weather periods. However, if you want warm water from spring to late autumn, the only option is a "real" heater (gas, heat pump...). At low temperatures, basically only gas remains.