Insulated old building from 1921: Conversion from gas heating

It doesn’t look any different with the heat pump either. You only need hot water. That costs me about 8 cents a day with the heat pump.

So you make hot water for €2.92 a year. Respect. :D

@TE: if it already fails at €300 (€200), or you don’t want to spend that, you can bury the project.

1993 and well insulated don’t really fit together for me. What exactly is the wall construction?

Calculating the heating load and determining the flow temperature are the first steps…

Also interesting would be the sqm and the heated sqm as well as room temperatures…

So you spend €2.92 on hot water per year. Respect. :D

No. It's actually €29.20 ;) Thanks to photovoltaics, it works. Hot water preparation once a day with +/- 1kWh

So with 75° supply temperature there is a heat pump. One should aim for <40° at 0° outdoor temperature. And in general: surface heating systems are more effective: ceiling heating, wall heating, or underfloor heating. Since this is not possible in old buildings without tearing everything up, one can use type 33 radiators which also have a larger emission surface than type 22 for example. This allows you to lower the supply temperature, which saves costs. I am still in the process of reading up on this, so I can’t easily help you with your specific heating system. The first step would be to lower the supply temperature/the heating curve. This also increases efficiency with the gas heating. Then you can see if the insulation is sufficient for a heat pump and if you can lower the supply temperature far enough. This only works when it is cold.

It could really be that the construction actually doesn’t need such a long lead time and it’s just set wrong (schonimmasojemacht!).

With your low gas consumption, it should actually be possible. Just as a side note: 11,000 kWh consumption. You still have to subtract the efficiency of the gas heating. Let's say 10,000 for a round number. This amount of heat has to be produced by the heat pump. A heat pump produces more than one kWh of heat from one kWh of electricity. This is indicated by the COP. For new buildings, you aim for 4 or better. With radiators, it's rather 3. So 10,000 kWh / 3 = 3333 kWh electricity. Depending on the electricity price, that's about €1000 per year for heating. And the COP depends on the flow temperature, which is why it is so important. With that, you can roughly do comparison calculations in your head. Sometimes the efficiency of the old heating system is only 70%, but professionals need to check that. Then the required amount of heat would also be reduced.

So I note:

1. Heating load calculation with the engineer
2. Forward flow temperature. Discuss with the plumber

We have for a 100m2 house (100m2 of which are heated and in the basement we have almost 40m2 more, which are unheated but could be heated), REH meaning on 3 sides without neighbors, the mentioned almost 11,000 kWh gas consumption and almost 2200 kWh electricity consumption – those are good values, even if the forward flow temperature might be set too high. We have 20°C on the ground floor, about 21°C in the children’s rooms on the 1st floor and about 22°C in the bathroom there, about 18°C in the attic (where only our bedroom is) in winter, although we hardly heat there at all. Upstairs we only have 2 of the 3 radiators in operation and they are set to 1. We still have to insulate the ground floor floor; there is still potential there. The basement ceiling is a vaulted ceiling with many pipes running along it, so insulation there is not practical and we wanted to wait with the insulation of the ground floor floor until it is clear which new heating system will be installed.

Wall construction: The previous owner never showed up, everything went through the realtor, so we don’t know anything precise. From the inside I can say there is plaster, then masonry made of typical red bricks 20cm thick as it looks. Then comes the insulation, whose thickness I measure as 21.5 cm including the exterior plaster. But I do not know what kind of insulation it is. The attic was newly insulated in 2017, with insulation between and under the rafters. I would have to check the thicknesses.