ᐅ Old gas heating system broken – need a new one, but what kind?

Good morning,

we bought a house that was built in 1936 and renovated in 2013.
Last year we viewed it and decided to buy it. Considering that the heating system dates back to 1997, we thought we would need to replace it “soon.”

House: approximately 145m² (1,560 sq ft) of living space, insulated roof, thick exterior walls. Double-glazed windows, chimney in the living room.

The chimney sweep wanted to shut it down two weeks ago because there was a strong smell of gas in the basement. Since we keep the windows open downstairs and have two small children, he decided against it. On his recommendation, we should get a new heating system because repairing the current one would be a waste of money.

We have now had four different heating companies inspect the house. The discussion came up (because I wanted to explore alternatives):

• Gas condensing boiler – a gas connection is available, it would be cheaper but is not subsidized (due to CO2 taxes, depending on gas prices).
• Pellet heating – mixed opinions – one expert said it wouldn’t work in the basement due to high humidity (another specialist said that’s nonsense) – higher initial costs – pellet prices are similar to gas prices and it is subsidized up to 35%.
• Log wood stove – high initial cost, needs to be refueled by hand regularly – no clear information on subsidies.
• Air-to-water heat pump – subsidized, the heating specialist took measurements of every single room including ceiling height to calculate the heat demand for the whole house and size the heat pump accordingly. He said he has good experience with it – but electricity prices will rise… it would also need a higher seasonal performance factor to be worthwhile.

Since we currently have a 27kW (36 hp) instantaneous water heater in the basement for hot water, the question is whether that should be removed and the new heating system used to heat the water as well.

We are planning to install a 10 kWp photovoltaic system on the roof anyway.

I know this is a personal decision, but I would like to become a bit more independent from fossil fuels.

I hope you can help me a little!

Best regards

Well, just add your versions with what it should absolutely cost.

I’ll guess:

Gas condensing boiler somewhere around 4,000–7,000 euros (about 4,400–7,700 USD)
Pellet system over 20,000 euros (about 22,000 USD)
Wood log stove—welcome to the Middle Ages—over 15,000 euros (about 16,500 USD)
Air-to-water heat pump is probably crazy for a building of that age due to the very high heating demand. Minimum cost for new radiators as well, over 15,000 euros (about 16,500 USD)

Switching the domestic hot water supply away from the tankless system is not a bad idea but basically amounts to a renovation. You should have done that before moving in. A 20-year-old gas boiler is already close to the end of its life, not to mention the consumption costs. You really missed the sensible time last year.

For me, it’s clear that a gas condensing boiler is the reasonable solution. Subsidies won’t change that.

We bought the house in December and were only able to move in by mid-January.

There are already new radiators in the house, and the bathroom has underfloor heating.
So far, I have received one offer:

• Gas condensing boiler Therma Modula 25 kW -> complete with installation €10,700 (Energy efficiency: A)
• Pellet heating system 6-16 kW with 4 t storage -> complete with installation €23,685 (But there is a subsidy of up to 35%) (Energy efficiency: A+)

Nissandriver schrieb:

So, new radiators are already installed in the house, and the bathroom has underfloor heating.

If you want the heat pump to be reasonably efficient, you need both to be designed for low-temperature operation. That won’t be the case here. So, you will need to replace them.

Get a comparative offer for gas again.

Nissandriver schrieb:

We bought the house in December and could only move in mid-January.

Renovation work should be done BEFORE moving in.

Take the gas boiler, and if necessary, recalculate whether 25kW are really needed. Also, check other suppliers. It can be installed in one day, and then you will have about 20 years of trouble-free operation.

guckuck2 schrieb:

If you want the heat pump to be at least somewhat efficient, both components need to be designed for low temperature. That won’t be the case here. So you’ll need to replace both.

Get a second quote for gas as well.

Renovation work should be completed BEFORE moving in.

Except for the heating system, everything was renovated in 2013. And we were assured that the heating would last a few more years. Apparently that was not the case, and according to the lawyer, there’s nothing we can do..

I will get some more quotes..

Mycraft schrieb:

Go for the gas boiler, run the numbers again to check if 25 kW (34 hp) is really necessary, and also look at offers from other suppliers. It can be installed in one day, and then you’ll have about 20 years without issues.

Okay, I’ll get a few more quotes from nearby.