ᐅ Which type of heating system would be the most suitable for us?

Hello everyone,

We will be building our house next spring. It will be a two-family house (a type of semi-detached house) with a total area of about 230 sqm (2,475 sq ft) – but with only one heating system.

We had initially planned to build a KfW70 house with a gas condensing boiler combined with a solar system. However, we are now having some doubts. Would it possibly make more sense to use an air-to-water heat pump? This system generally incurs no fuel costs and offers independence from gas prices. We have also planned underfloor heating.

Another question is: If we were to choose an air-to-water heat pump, would we still need to build to the KfW70 standard? KfW70 offers the advantage of significant heating cost savings. That was one of the main reasons for considering it. But if the heating system doesn’t involve fuel costs, wouldn’t it make little difference whether we build to KfW70 or according to the Energy Saving Ordinance 2009?

I would appreciate any advice.

Best regards

Kati

Hello, are these supposed to be joke questions for November 11th?

Kati27 schrieb:
...We had actually decided on a KfW70 house with a gas condensing boiler combined with a solar system. But now we are doubting again.

Why?

Kati27 schrieb:
...Would it possibly be more sensible to use an air-to-water heat pump? There actually shouldn’t be any costs here, and you are independent of gas prices.

What do you mean by that? Besides, you would then be dependent on the time-of-use tariffs (day/night rates) of the local utility company.

Kati27 schrieb:
...Another question would be: If we took an air-to-water heat pump, would we still have to build according to KfW70 standards? KfW70 has the advantage that it saves considerable heating costs.

No one has to choose KfW70! However, you have to meet the limit values if you want to receive subsidies! Also, what exactly do you mean by considerable? Considerable heating cost savings can also be achieved in other ways. 😉

Kati27 schrieb:
...But if the heating system generates no costs, wouldn’t it be irrelevant whether we build to KfW70 or to the Energy Saving Ordinance 2009 standards?

A heating system that causes no costs would be an absolute novelty and is unknown to me so far! What exactly do you mean by that?

Best regards

Hello,

thank you for the quick response. We decided on a gas heating system combined with a solar setup because it is simply affordable and standard with most providers.

We had only heard about this air-to-water heat pump, which is cheaper to purchase but supposedly costs NOTHING more afterwards (meaning in operation). I don’t know how that is supposed to work; it seems strange to me. For example, Viebrockhaus installs this system in all their houses. Although Viebrockhaus is too expensive for us, we are now interested in this system.

Could you provide information about it? Would it be worthwhile?
And what is meant by the HT/NT special tariffs from the local energy supplier?

Thanks and best regards,
Kati27

Hello,

Kati27 schrieb:
... So we decided on a gas heating system with a solar thermal system because it is simply affordable and standard with most providers.

This does not necessarily mean it is economically advantageous for the homeowner. With the solar thermal system, the Qp´´ value is artificially improved "on paper" (Energy Saving Ordinance / KfW certification). When such basic systems are tested in practice, the result is often disappointing!

Kati27 schrieb:
... We only heard about this air-to-water heat pump, which is supposedly cheaper to purchase but then allegedly costs NOTHING to operate.

This is a blatant lie. Although an air-source heat pump can utilize a certain amount of environmental energy, the compressors and evaporator require electricity, as does the additional heating element.
Still, an air-to-water heat pump can be more advantageous than electric gas heating, provided the conditions are suitable.
The problem with the gas option is the solar thermal system! However, it can also be avoided.

Kati27 schrieb:
... For example, Viebrockhaus includes this system in all their houses. Even though Viebrockhaus is too expensive for us, we are now interested in this system.

I have access to significantly different results on a larger scale. Depending on the option, different configurations are used, not just by this provider.
I can only strongly advise great caution and definitely recommend not signing any contract without independent, sales-neutral consulting and calculations.

Kati27 schrieb:
... Would it be worthwhile?

There is no general answer to this if reliable results are desired. This must be calculated based on the specific building, climate data, and user behavior! Only with these results can it be assessed which solution is truly economical and sensible for the homeowner.

Kati27 schrieb:
... And what is meant by HT/NT special tariffs of the local EVU?

These are special tariffs for supplying heat pumps.

Best regards

Hello,

what are the basic requirements/information needed to choose the right heating system? We are quite uncertain about which system to decide on.

I cannot estimate the consumption yet. I can only say that our house will be about 240 sqm (2,583 sq ft), we want a KfW70 standard, and initially, only three of us will move in. In a few years, of course, children may be added.

Regards

Kati27

Hello,

Kati27 schrieb:
...what are the key requirements/information needed to choose the right heating system? We are quite unsure which system we should decide on.

These are mainly the building data (geometry, building components used [U-values], ventilation, building airtightness…), the building location (position, orientation…), user behavior (number of occupants, hot water consumption, room temperatures…). Ultimately, all factors that determine the energy demand (heating, hot water). The consumption can then be obtained in connection with the respective technical solution! This allows for comparison of different options.
The results from energy saving regulations/building efficiency certifications like KfW are generally not suitable for this purpose due to their standardized boundary conditions. However, building data from these can still be used!

Kati27 schrieb:
...I can’t yet estimate the consumption.

Even "experts" sometimes have difficulties with that 😉

It always amazes me how carelessly construction contracts are signed despite the significant financial consequences involved.
When I then look at some of these, partly botched systems, I often get standard responses from homeowners:

"We were told that...."
- but nothing is written in the contract!
"If we had known that, we would have...."
- inform yourself beforehand and get independent advice.
"I can’t make any changes now, can I......"
- usually only corrections within certain limits are still possible (case-dependent). Prevention is always better than cure!
"We assumed that a professional company would...."
Yes, probably, and it will heat up as well – but as a result of insufficient energy efficiency, the consumption costs are far too high, so what now?

I rarely make broad generalizations, but as a current observation: for an energy-saving regulation or KfW70 level building, for example, an exhaust air heat pump should not be used as the base load heat generator, whereas an air-source heat pump can be quite sensible!

Equally surprising is how meticulously and in great detail people select tiles, the bathtub, a dormer, the room layout, etc.
Meanwhile, the essential foundations of efficient building services engineering (precise calculation/dimensioning) are ignored or not even noticed. Almost every compromise presented by the seller is accepted.

Without reliable and verified consumption forecasts, I would not build or buy a building!

Best regards