Away from fossil fuels - House from 1999

Good day!

I am the kind of person who likes to tackle and solve things before they become a problem. Therefore, I am considering whether there is a reasonable way to say goodbye to heating oil without switching to natural gas. Can one roughly say what is possible based on some key data?

The total usable area of the house is 300 square meters, of which 178 square meters is living space. The difference is essentially the basement rooms, which I partly use for my freelance work. Two adults and one child live in the house, both adults also work in the house. We consume about 3,000 liters of heating oil per year (i.e. 10 liters per square meter including hot water) and use about 8,000 kWh of electricity, as we also charge two electric cars.

The house consists of 24 cm thick Liapor solid elements, which buffer very well: it remains cool for a long time in summer and warm for a long time in autumn. In front of that there is 6 cm of mineral insulation, then a 4 cm air gap and then a brick veneer. The wooden windows have double glazing. The house has a carpenter-style roof structure with 20 cm of mineral insulation, and during the interior construction we paid great attention to precise airtightness.

The oil central heating system is now 22 years old but still runs very well. We have no underfloor heating, but radiators in every room. The flow temperature is approximately 40 degrees, and we operate a heating curve that is roughly as flat as that of underfloor heating. Our roof shape (hipped gable roof with four gable dormers) is not suitable for photovoltaics, but on the garage (gable roof with about 30 degree pitch, ridge running north-south) we have space for about 70 square meters of photovoltaics, half facing east and half west, free from shading by trees. Between the garage building and the house I have already run a 5x16-square NYY cable (50 m long), because the cars are charged there. So if photovoltaics were installed on that roof, the inverter and control system could be hung in the garage, and there would also be room next to the garage for battery storage. There is also enough garden space for ground collectors.

Now I am wondering: Is there a reasonable overall concept involving photovoltaics, battery storage, heat pump, and flat plate collectors? I would like to tear out the oil tank but do not want a gas connection. Under these conditions, can a relatively high degree of self-sufficiency be achieved over large parts of the year so that only relatively little electricity needs to be bought in, but without the risk of eventually being cold?

Ideally, I would like to commission an independent energy consultant with a corresponding concept assignment, but I have no idea how to find one who approaches this in a truly technology-open manner, but also keeps an eye on political directional decisions, which, of course, cannot yet be known how they will look in the coming years. If you act too early, you might regret it because much stronger subsidies may come later, but if you act too late, you might have to be annoyed for too long about exploding oil and electricity prices. Apart from the fact that I simply no longer find it acceptable to burn oil or gas.

Matthias

Your main problem will be how much supply temperature you have needed at most so far when it is really cold outside. How low is the design temperature for your area according to DIN? (Here it is -13°) The existing radiators might already be "too small" for that.

Alternatively, with the existing radiators a bivalent heating system would be possible, where the second heating system (gas condensing boiler?) only heats up at low outside temperatures (e.g. < -5°). Since it only runs rarely per heating season, it could even run on propane (n*33kg bottles) if natural gas is not connected in your area. The rest is then handled by the heat pump.

Photovoltaics as direct heating won't help, as they typically also provide nothing when it's too cold outside.

Or alternatively, enlarge the radiators for the heat pump. Possibly wall heating?

A wall heating system would certainly be a nice solution, unlike underfloor heating, but that would also mean an exorbitant effort because the entire screed would have to be torn out, and then the house would be uninhabitable for an estimated half a year.

I would have to observe how much the flow temperature rises when it is really cold outside, but we haven’t had that situation in Berlin for years. I find the idea of having a propane gas cylinder as a fallback option quite interesting. You could hide it somehow in the front garden among plants, just as you have to do with the heat pump.

Natural gas would be available in the street, but I don’t want to have a gas connection, especially if I might only need it a few days a year.

So a house from 99 and then 3000 liters consumption, in my opinion, is very much. My sister also built in 99, the living area should also be around 160m2 but only 800-900 liters of oil + 2-3 steer wood. I would first look where the oil is going.

Underfloor heating can also be milled. Similarly, a ceiling heating is possible. You will probably not avoid enlarging the heating surfaces. The flow temperature should be as low as possible this winter, heating 24/7. I can imagine that heating the basement rooms consumes a lot of energy. Additionally, you can have a heat meter installed so that you know how large the energy demand of the house is.

Enough garden space for ground collectors would also be available.

The option of a heat pump as a heat source would be obvious, you can generate electricity yourself for it, and also buy it as green energy or normal.
Maybe your car battery is the electricity storage of the future, which also supplies the heating.
Insulating the basement to reduce overall consumption is an option.
Remote diagnosis is difficult.
I consider climate forecasts with no frost and weeks below -15 degrees to be a crystal ball that can lie.