Chimney inside or outside?

Hello Knallfrosch,

I also don't find external chimneys attractive. If they are new, it might still be acceptable. But later on, algae and moss grow on the brackets and they need to be maintained/cleaned. The facade also doesn't remain completely stain-free.

Sealing an internal chimney at the roof is not complicated. Especially if you don't have roof insulation (cold roof, thumbs up!), it's not a problem. If a leak does occur, it will become visible quickly and can be relatively easily fixed. This is somewhat more problematic with rafter insulation, but from my point of view, it is not critical.

The wall installation of an external chimney also has to be sealed, and depending on the wall structure, that is not trivial.

our chimney stands on a straight wall and the sealing didn’t seem to be a problem. in a corner of the house, the builder didn’t want to do it (hip roof), as that could cause enormous problems. it was never an option for us anyway. for the next build, I would place the chimney inside in such a way that it is not visible in the living room but in the room behind. (so the wall in the living room is flush) the utility room would be an ideal location for this, for example. another advantage of proximity to the utility room is the very simple water drainage from the chimney (simply connected to the wastewater from the utility room). most people don’t do this, the rainwater gets in and then stands in the chimney until the next firing.

Heating: No, there is currently no calculation that somehow manages to make a heat pump economically viable.
In recent years, the gas price has always gone down and the electricity price has gone up.

The gas price has been fairly constant over the past few years, sometimes slightly declining. The same applies to electricity prices.

A comparative calculation basically depends on the individual consumption costs (including fixed charges) on site, as well as the investment costs. In the latter case, the calculation for gas is often somewhat simplified. Because the burner may be cheaper, but the connection is not free (one-time cost), the chimney is not free either, and the maintenance and the chimney sweep also need to be paid continuously.

That is why the heat pump is artificially made to look better in the Energy Saving Ordinance calculations while gas heating is calculated poorly. In a new building, you usually have to install a controlled residential ventilation system and/or plenty of solar thermal to still be allowed to install a gas heating system.

A regenerative share is mandatory. The primary energy calculation is set up in such a way that gas without a regenerative share is no longer possible. You have already named controlled residential ventilation or solar thermal as possible solutions (connection to biogas would be another, if possible). Whereas "plenty" of solar thermal is not needed, most new buildings I see have two solar thermal elements on the roof. Heat pumps are not "artificially" calculated either. The primary energy factor has been adjusted, yes, but the electricity mix in Germany has also changed, so that is comprehensible. Certainly, a portion of subsidy may be included to promote this heating technology.

A photovoltaic system is initially not very useful for your heat pump. Heat pumps want 400 V / three phases while the photovoltaic system supplies 240 V / two phases. Doesn’t match...

No offense, but that is simply nonsense. Three-phase inverters are practically standard and mandatory from around 4.x kWp system size. Heat pump and photovoltaic fit together like hand and glove.

And you need your heat pump in winter, so you can forget about the yield of photovoltaic.

The photovoltaic power will probably not be enough to fully supply the heat pump (although that also depends on the system size and the heating load).
But one can also argue that heat pump + photovoltaic fit well together especially in winter, because the heat pump immediately uses all the electricity coming from the roof and thus raises self-consumption extremely high. That bit of self-generated electricity is therefore particularly economical when viewed in isolation.

if you put something on the roof nowadays, then solar. photovoltaic on a small scale is simply nonsense and significantly less profitable than heat (solar). the efficiency for electricity is significantly worse and gets even worse the warmer it gets (somehow paradoxical, since it normally also gets warmer when the sun is shining ^^). in the end, it’s just calculations and a lot of nonsense and you have to know for yourself what you want. solar is cheap and today "standard" if you want to put something on the roof of a single-family house. after all, can (not must!) eventually pay off, although you also have some work with it and it can cause problems. as already said, the "ventilation system with heat recovery as a regenerative part" is also approved and a ventilation system is anyway always sensible today and brings real comfort. whether you save 10€ on heating costs is totally irrelevant, since heating costs for a new house are anyway ridiculously low compared to all other ancillary costs. on the other hand, if you no longer need to ventilate (but can) and no longer have to worry about mold (it cannot of course compensate for leaks in the roof), that is a real gain in comfort.

Hi,

sorry, I actually didn’t want to start the old "gas versus heat pumps" war of beliefs.

Heat pumps are not "nicely" calculated either. The primary energy factor has been adjusted, yes, but the electricity mix in Germany has also changed, so that is understandable.

Yes, the electricity mix has changed. But it is not constant throughout the year. In summer, there is indeed a very high share of renewable energies. In winter, and even more so during a winter night, it is much lower. And that’s exactly when the heat pumps are running! And happily consuming electricity from environmentally friendly lignite or the equally environmentally friendly nuclear power from France...

Many greetings,

Andreas

And then happily waste the electricity from the environmentally friendly lignite or the equally environmentally friendly nuclear power from France...

And the pumps of the gas condensing boiler waste exactly which electricity...?

Rhenish greetings