Which heating system is suitable for old buildings?

Hello, I have a fully renovated old building (built 1957), completely insulated and with solar thermal, and I need to replace the current gas boiler. Now I am considering whether it should be a gas condensing boiler or wood pellets. Does anyone have experience with both and can help me?

I am a fan of wood pellets, I don’t like gas at all (I once explained that somewhere). You can get several thousand euros of funding from [Bafa] for pellets, there is nothing for gas. You can also integrate a pellet stove (water-bearing) decoratively into the living area. If wood, you can also consider a log boiler or wood gasifier, it offers more than oil, gas, or pellets. We don’t have a pellet storage, that would not be technically possible for us, but they can be blown in or delivered as sack goods.

How often do you need to refill with the sack goods?

So my pellet stove has a minimum consumption of 1 kg per hour (4 kW minimum output), so a 25 kg sack would last a whole day, but the tank holds 37 kg. That makes a runtime of just under one and a half days when running at minimum output. This is a boiler with manual feeding, so without an auger (Red compact Slim). Quite a difference from the wood stove, where I have to add fuel every 20 minutes.

How difficult is this refilling? I (woman) live here with my 2 children... can I manage this on my own?

Take the sack, open the flap, put the sack in, done ;) (without plastic of course) There are also smaller packages, 15 kg is a common size, I can even lift that easily. I am also female with little "muscle background". The effort also depends a bit on how far the delivery location (pallet) is from the storage location. For us it's 50 meters, last summer we easily brought in almost 2000 kilos of wood briquettes in 2-3 hours with a break, the two of us. Using a sack truck works really well.