Assessment of heating system retrofit costs

Hello!

We are currently planning our single-family house (~145m² + basement) and are now completely uncertain about heating! Almost everyone who wants to build a house for us says something different. It ranges from "I would never build without a heat pump and ventilation with heat recovery" to "oh, anything other than gas is nonsense, far too inefficient!" to "What, KFW70? Why do you want to spend money on that?"

I understand the inefficiency at really low temperatures, but if it's not -15°C cold, it works pretty well, right?

While browsing, I came across hybrid heating systems that automatically integrate a gas boiler when the heat pump's efficiency is too low, which then provides additional support. To me as a layperson, that sounds like a good idea at first. What do you think? Of course, compared to a pure heat pump, I still have to pay for the connection, but as an alternative to pure gas heating...?

In general, I would have found a ground-source heat pump quite nice, but since we have a slight slope, some have excluded that from the start.

Many thanks in advance!

Hello,

yes, the heating question kept us busy for a long time too... ;)

in the end, we settled on an air-to-water heat pump including central ventilation with heat recovery.

Well, if it really gets too cold, we will also have to use the integrated electric heating rod. However, we will easily be able to cover the electricity demand with our photovoltaic system on the roof. Our soapstone stove will also contribute its part to always keeping it pleasantly warm.

My brother has been living for three years in his house with almost identical technology (different manufacturer, but same basic concept) and he even earns a few hundred euros every year with his photovoltaics, although he also had days in winter when the heating rod was in use.

If you don’t already have gas in the house, I would personally rather invest the money for the gas connection in a photovoltaic system – then you also benefit more from it in summer...

But it is very important that you get a heat pump tailored to your requirements. An oversized or undersized system only costs unnecessary money or comfort...

Regards,

Dirk

Hi!

Maybe a zeolite gas heat pump would be something for you.
It's highly interesting.

Regards
Sebastian

Hello,

....About everyone who wants to build a house for us says something different.....

That is the nature of things and makes it infinitely difficult for builders to make the right decision.
You should never be advised by the person who is also selling and/or installing at the same time, but always by an external, sales-independent expert!
The contents of embellished, colorful advertising are mostly never reflected in the contract contents.

....It varies from "I would never build without a heat pump and ventilation with heat recovery" to "oh, anything other than gas is nonsense, far too inefficient!" up to "What, KFW70? Why would you want to spend money on that?"....

This sufficiently characterizes the current situation. No construction project is the same as another, even if the building were identical, since the influencing factors are extraordinarily diverse and significantly differentiated.
Without a solid and precise basic investigation, you will not get an economical solution here.
Moreover, one should be quite critical when assessing opinions on the internet. Mostly, the advisors are anonymous, without any professional training, and have no liability, etc.
Individual experiences of builders are indeed very interesting, but not transferable to other construction projects!!!

...The inefficiency at really low temperatures makes sense to me,...

Well-planned air heat pump systems achieve an annual performance factor of ~ 3.5, provided everything fits and matches.
At low outdoor temperatures, the actually usable energy content of the outside air is indeed lower, but what percentage of the annual heating energy is attributable to this? For example:


This is of course dependent on the respective climate location. I always use these data in my planning!
In well-dimensioned systems, the share of an auxiliary heating rod is barely < 1% of the annual heating energy demand. Child's play in the overall context!
Fully modulating split units are the first choice here!

...Sounds like a good idea to me as a layman. What do you think? ...

Combi devices are found in almost all partial areas (heat generators, storage...). They are indeed compact, but generally always represent a modest compromise. Rarely economical overall.

..., but as an alternative to pure gas heating...?

Neither fish nor fowl. Based on the results of an exact and solid basic investigation, the suitable solution can be easily found.

...In general, I would have found a brine-water heat pump quite nice, but since we have a slight slope, some ruled that out from the start...

Whether some people's opinions are really economically reliable to make a significant investment decision, I would not assume ;-)
There would be many other possibilities.

Regards

..... My brother has been living in his house with almost identical technology (different manufacturer, but the basic concept is the same) for three years, and he even earns a few hundred euros every year with his photovoltaic system, although he also had days in winter when the heating rod was in use...

I have already planned and dimensioned this basic concept several times with brine heat pumps and air heat pumps. Heating, hot water, ventilation, cooling, cooking... can sometimes be possible at zero cost, sometimes there is even a surplus of a few euros! Of course, the investment for the photovoltaic system costs extra. But usually, this is not a problem. As always, => case-by-case consideration! Unfortunately, mistakes are sometimes made in the preliminary assessment here as well. The decisive factor is always the annual energy balance, not the individual result on January 15 of a year! Best regards

Hello Dirk,

Well, if it actually gets too cold, we will also have to heat using the integrated electric heating element.

You see me puzzled ... why should you have to heat using the integrated heating element - which is exclusively intended to defrost the outdoor unit in frost?

Rhine regards