Heating/Single-family house new construction/ which is sensible/ costs/ benefits for 20 years

Hello... we are about to start building soon, a simple single-family house with 140 sqm of living space and Kfw70 standard, heat recovery through the ventilation system, windows with 0.5 glazing, etc... Now we are facing the decision of which heating system to install. The options are natural gas with solar for domestic hot water support, natural gas with solar for domestic hot water and heating support, air-to-water heat pump (possibly combined with solar support), or geothermal heat pump with ground collectors... Regarding purchase costs, it doesn’t really matter since we have enough funds for all of these; with gas, for example, a lot of piping would be needed (30 meters), and for the generally more expensive geothermal heat pump, the earthworks... What matters to us is what pays off in the long term? It is important to us that we have something for the next 10-20 years and do not end up paying more for a cheap system after 10 years due to high running costs. Of course, also regarding maintenance, according to the heating installer, a gas system can be worn out after 15-20 years, which is not bad, but the question is whether a new one would be more worthwhile then than, for example, a geothermal system that is supposed to last 30 years... Likewise, the energy cost question: is the heat pump running on electricity (assuming normal household electricity since I don’t believe special tariffs will last forever and anyway, with the nuclear phase-out, there will be a big shock in electricity prices) cheaper than the gas system? Of course, neither I nor anyone else knows what electricity and gas will cost in 10-20 years, but most agree that electricity prices will rise more than gas... And also the topic of solar: the difference between just domestic hot water and heating support is already huge; the question is whether it really pays off? I find it incredibly difficult to decide which system or combination makes sense.

Hello,

...Now we are facing the decision which heating system to install. The options are natural gas with solar for domestic hot water support, natural gas with solar for domestic hot water and heating support, air-to-water heat pump (possibly together with solar support), or ground source heat pump with flat collectors... As far as acquisition costs are concerned, it’s all pretty much the same since we have enough funds available,...

Even if the budget is sufficient, you don’t necessarily have to choose an uneconomical solution for that reason.

...What matters to us is what pays off in the long run? It is important to us that we have something for the next 10-20 years and not pay more after 10 years for a cheap system through high operating costs.

Correct, there is no more sensible approach!

...I find it incredibly difficult to decide which system or combination makes sense

Correct, without a solid basic assessment it won’t work, if you want to rely on reliable information. Here the actual demand (capacity, energy) for heating, hot water and, if applicable, ventilation of the building is determined based on building parameters, the climate location, and user behavior. Based on this, the expected consumption can be determined in connection with various technical solutions.
With these consumption values, the respective investments or capital service for them can be reliably evaluated.
Without concrete numbers => guessing, assuming, presuming, i.e., guessing game!

No suitable basis for a significant and long-term investment decision.

Regards

And the actual consumption, unfortunately, changes in life... For example, in our case, the two children's rooms were hardly heated during the time when the kids were still babies or toddlers, as an optimal sleeping temperature of 18 degrees only activated the heating in the rooms on extremely cold days. But as the children grew older and the rooms were no longer used as bedrooms (our bedroom, for example, is not heated at all) but as living spaces for homework, daily living as a teenager’s room, since then they have been heated much more, a room temperature of 21-23 degrees is a whole different level and then the "theoretical" calculation of the energy consultant breaks down, as this was not taken into account or included in any alternative model.

Therefore, no theory can really give you clarity, at most it can give you a rough direction... Even if you heat your living room differently than calculated or you use the calculated fireplace differently or not at all, it looks different again...

As a decision aid to select 2 out of several models and decide between them and find a direction, it is certainly helpful... But it is usually not available for peanuts because it is very elaborate and, due to the trend, certainly calculated to be expensive, so one should ask in advance what it costs to consider whether one wants to invest the money, which then has to be earned back again...

Personally (this is just my personal opinion and not advice or anything similar) I talk to the heating engineer you trust or to several, because they have daily experience in practice and this has worked great for everyone else in our building area. They know everything from practice and deal with it daily in all kinds of situations; they can not only give you a theoretical recommendation on the computer or tell you what costs what... Our energy consultant was at the same time our heating installer, so we have accounted for the invested money in the contract. Most people in our building area have listened to the advice of their heating installers and I have to say, in similar buildings the same systems are used and there is no one who stands out with running costs or investments... But it may be different everywhere else and certainly there are also those who only want to install what requires the least work or earns them the most...

What you do is of course your decision

....since then much more heating has been done there, room temperatures of 21-23 degrees is a completely different matter and the "theoretical" calculation of the energy consultant collapses because it was not taken into account or included in any alternative model.

Why not? Any "eventualities" can be taken into account. Anyone who does not realize that small children also grow into teenagers has probably done something wrong
An energy consultant is often overwhelmed by this, unless he is also an HVAC planner.

...But usually it’s not easy to get this because it is very complex and, due to the trend, certainly calculated expensively, so you should ask beforehand what it costs in order to consider whether you want to invest the money, which then also has to be earned back...

Economic efficiency is always important, which is why a solid basic assessment is also so important.

...Personally (but that is only my personal opinion and not advice or anything like that) I talk to the heating installer of your trust or with several, because they have the experience every day in practice and that has worked great for everyone else in our building area.

Almost every heater produces warmth, but very few are actually efficient. In other forums there are plenty of examples where this trust was often severely disappointed because it is not part of the contract with the heating installer. Here mostly superficial sales are made. Often systems are installed without sufficient planning. Most operators don’t even realize that the consumption is actually far too high! How could they, since a real comparison option is completely missing.

...They know all that from practice and deal with all kinds of situations daily, they don’t just give you a theoretical recommendation on the PC or tell you what costs what...

From practice I could also tell you, especially about the many botched systems where it was not properly sized.

...and I have to say, in similar buildings it’s the same systems and there is no one who sticks out with the running costs or the investments...

Highly unlikely, because for this the buildings, system technology and user behavior would have to be completely identical!

best regards

Completely unlikely, because for this the buildings, system technology and user behavior would have to be completely identical!

v.g.

I would rather question that more thoroughly than immediately dismiss it as "completely" unlikely. Maybe he meant something quite different than understood (which is always the problem with written words, who understands what how). I don’t believe he means that they are all the same houses with the same users and the same heat demand etc., but that they have the same system in different houses with different people in the house and, for example, from one kWh of electricity you get approximately the same amount of heat output or from the cbm of gas or whatever it is about (nothing is specified). I understand it like this: for example, if 2 houses have the same system, one doesn’t run super cheaply (converted to heat and energy demand, or whatever it should be called) and the other super expensive, but both are very close to each other.
Why should he write something that isn’t true, or why should neighbors or friends or whoever lie to him if he discussed it with them?

Regarding the actual topic: If the architect is supposed to make the exact calculation for the actual demand, he wants 1000 euros for it; with the calculation I can then go to the heating installer or wherever and have them figure out what costs what and what running costs are how much.
Hmm, 1000 euros is quite a lot of money... I don’t yet know if I want to afford that to ultimately save 5 euros a year...

We have currently brought in 3 heating installers and will first look at what they say and propose, and based on experience, decide.

By the way, we could also use district heating, but with a 400-euro annual basic fee (without even having used any heat yet) and connection/installation costs of 15,000 euros, a 10-year contract and a "Polish fleet" that didn’t work properly with excavators at 2 other neighbors, that’s out of the question.

Hello,

so if you already have installers at hand, I would also ask them if they create a heating load calculation, because they also need some kind of basis for selecting the size of the system. And having it done by the installer is often more cost-effective than by the architect, since architects often offer this as an additional service at a higher price. And even if the installers do not want to do the calculation, I would at least have it explained to me exactly on what basis they made the heating selection (especially regarding the size and modulation range (i.e. from/to kW)), so that you don’t end up comparing two completely different systems if different capacity sizes are offered.

Best regards Erik