Old oil heating, 2-family house

Hello everyone,

I am the owner of a two-family house with an old oil heating system, which I would like to renew in the near future. What would you recommend here, preferably also an alternative and regarding subsidies. What kind of cost should I roughly expect?

Here are the facts and details:

Two-family house built in 1971
occupied by 4 people
solid construction, exterior walls not insulated, insulation planned for the next few years
partly new windows, will be renewed soon
1st apartment 200m², 2nd apartment 85m²
Oil heating Heimax NOK 33, 1993
Underground tank, 10,000 liters
no gas connection available
total consumption approx. 3000 liters
Sonnenkraft collector 2003, SK500 N, 15.4m², storage 750 liters
In apartment 1 there is a wood stove, approx. 8 kW

I hope I have provided all necessary information.

Thanks, regards

Hi,
my mother just dealt with the topic in her house (about 250 sqm in two apartments) 2 years ago. In the end, it only made sense to install a new oil heating system. Since these are only available with condensing technology now, a smaller flue had to be installed in the chimney, a drainage option had to be created in the heating room, etc. Overall, she paid about 15 k€.

Heat pumps and the like are out of the question for you; for that, you need a well-insulated house with underfloor heating.

Your consumption is actually not that bad, it's about 30,000 kWh for 285 sqm of living space. A modern house of that size would still need 15,000-20,000 kWh.

The new heating system will not consume much less, at best 10%, no more. In other words, I would keep it until it breaks and only replace it then. If you're lucky, it will last until the construction boom has eased off and prices will then go down.

Best regards,

Andreas

First complete the planned insulation and then determine the actual heating load. If no new radiators are planned, then install new windows targeted where the room-specific heating load is highest or where the highest flow temperatures are needed to make it warm. If the heating load is known, you can consider replacing the heating system; for now, I would also keep it running and maintain it.

My dad has a similar problem. A few years ago, he insulated the house from the outside. Now he has replaced the small radiators with new larger ones. These have twice the depth and width. Fortunately, no problem with the space. He said that in the future he can heat with low temperature and replace the old heating with air heat when the opportunity arises.

In my opinion, you should:

[*]Leave the external insulation alone.
[*]Keep the heating until it breaks.
[*]Insulate the roof and replace the windows (if not already done).

Everything else would be neither economical nor ecological.

If you ever need to replace the heating system, oil again, gas (higher investment due to tank), or maybe in a few years a micro/nano combined heat and power unit would make sense. The latter only if you have a good electricity consumer. Electric car, neighbor, pool heat pump...

Addendum: My parents' house is comparable to yours, just a bit older. 300 sqm, built in '61, oil heating from '88, wood stove additionally and solar thermal. Roof is new, the second windows are still good. Consumption with three people is 1600 liters and 4-5 cubic meters of firewood. Nothing on the outside is touched, the chimney sweep says I should keep the heating running until it is decommissioned.

Family house built in 1971 occupied by 4 people Solid construction, exterior walls not insulated, insulation planned in the next few years

Insulating the exterior wall is in most cases the most expensive way to save energy. If not done as DIY or if a renovation is already necessary due to damaged plaster, the payback period is more than 10 years, sometimes not at all.

Built in 1971 likely no longer with solid brick but already with aerated concrete or perforated bricks or hollow blocks. What is the wall thickness? Faced with brick or plastered? Do you have building documents showing the structure of the exterior wall? Depending on the construction method, the U-values for this building year range between 0.6 and 1.4 W/m²K, which makes a big difference in whether exterior wall insulation is worthwhile or not.

Regarding the heating, if gas is available at the house, I would also get a quote for this. A gas boiler is cheaper than a new oil boiler, so you save the additional costs there. In operation, gas is then cheaper and easier. Definitely continue to use the solar collector, replace the storage tank if defective.

Generally, keep it running until it is clear what to do with the windows. Best to take triple glazing with warm edge spacer. Also, as already mentioned, insulate the roof properly and possibly the cellar ceiling from below – cheap and effective.

Only after this, replace the heating according to the new heating load and then size it smaller.

Funding: KfW – Program 430 grant, individual measures windows (U-value <0.95), gas boiler, roof (U-value <0.14), each 10% of total costs. Or KfW – Program 430 grant – heating package: 15% of costs if hydraulic balancing is carried out and additionally 15% for other simultaneous individual measures.

Depending on the federal state, the state banks and promotional banks of the states or municipalities have individual funding programs with additional grants, often combinable with the KfW programs.

So best to carry out everything together: