Heating Planning

First of all, I am not an expert.

It may be that this works with large low-temperature radiators. However, the air heat pump is only suitable for very well-insulated houses. Everything else becomes unprofitable and in winter you might possibly heat purely with electricity, because the heat pump in normal operation cannot compensate for the heat losses through the walls, roof, and base slab.
Of course, with high financial effort, you can wrap an old house from all sides so that an air heat pump works. I just don't believe that this is the case here.

When it comes to really dirty pots, really hot water is very useful!!! However, I only came across a possible problem with the hot water in heat pump technology because a colleague had a problem exactly there: to run his heating system with hot water (heat pump with [etdkollektor]) efficiently, he had to turn down the heating water temperature, and promptly his wife complained...

We generally have 54 degrees in the hot water tank (270 liters), leaving enough buffer when everyone is showering/bathing, etc... I also use it in the sink when I clean tools from dirty grease while working on cars, for example... but that's already close to the limit of tolerability even with thick dish gloves ;) Legionella is only a concern if the water in the tank stands for a longer time/during prolonged absences, for example if you only have a weekend house...

@illo what kind of heating system do you have?

And how many people are there in your household?

Hello Peterbocholt,

how large should the extension be, is it only to expand your apartment? What energy standard will it have? Energy Saving Ordinance, Kfw 70 or better? What is meant by “windows and insulation up to the latest standards”? Has a defined standard been achieved here? Once the parameters are set, a heating load calculation should be carried out. It is important to clarify how many people are supposed to live in the property. Assuming 5 people (2 x parents-in-law plus 3 x persons) with you, we come to a hot water demand of about 160 to 300 liters, which is not insignificant. Therefore, a central hot water supply should definitely be considered. This should be taken into account when planning the extension; perhaps pipe lengths can be reduced and thus the conversion effort in the existing house minimized. One option is a gas condensing boiler with a solar collector system, which provides not only hot water preparation but also heating support. If the two properties have significantly different energy levels, the gas condensing boiler provides sufficiently high flow temperatures, which can be implemented via possibly two different heating circuits (old building, new building).

Best regards, Erik