Which heating is most suitable for us?

Hello everyone,

We will be building our house in the spring of next year. It will be a two-family house (a kind of duplex) with a total of about 230 sqm – but with only one heating system.

We had actually decided on a KfW70 house with a gas condensing boiler with a solar system. But now we are having some doubts again. Would it perhaps be more sensible to take an air-water heat pump? There are actually no costs involved here and you are independent of gas prices. We have also planned underfloor heating.

Another question would be: If we now took an air-water heat pump, would we even have to build KfW70? KfW70 has the advantage that you save considerable costs on heating. That was also the reason for us to consider it. But if the heating system does not cause any costs, it would actually be irrelevant whether we build KfW70 or this Energy Saving Ordinance 2009, right?

I would be happy if someone could help me.

Regards

Kati

Hello, are these joke questions for 11/11?

...We had actually decided on a KFW70 house with a gas condensing boiler with a solar system. But now we are doubting again.

Why?

...Would it possibly be more sensible to take an air-water heat pump? There are actually no costs here and you are independent of gas prices.

What is meant by that? Moreover, instead you become dependent on peak/off-peak special tariffs of the local utility.

...Another question would be: If we now took an air-water heat pump, would we then even have to build KFW70? KFW70 has the advantage that you save significant costs when heating.

Nobody has to take Kfw 70! However, you have to meet the limits if you want to claim the subsidy! Furthermore, what is significant?
Significant heating cost savings can also be achieved in other ways. ;)

...But if the heating system causes no costs, it would actually not matter whether we now build KFW70 or this Energy Saving Ordinance 2009, right?

A heating system that causes no costs would be an absolute novelty and is not known to me so far! What is that supposed to be?

Best regards

Hello,

thanks for the quick response. So we decided on a gas heating system with a solar installation because it is simply affordable and standard with most providers.

Now we had only heard about this air-to-water heat pump, which is cheaper to purchase but supposedly SHOULD cost NOTHING anymore (i.e. in operation). I don’t know how that is supposed to work, it seems odd to me. For example, Viebrockhaus installs this system in all their houses. Even though Viebrockhaus is too expensive for us, we are now interested in this system.

Can you give me information about it? Would it be worthwhile?
And what does this mean: HT/NT special tariffs of the local EVU?

Thanks and best regards

Kati

Hello,

... So we decided on a gas heating system with a solar system because it is simply cheap and standard with most providers.

That does not mean it is necessarily economical for the builder. With the solar thermal system, the Qp'' value is beautified "on paper" (Energy Saving Ordinance/KfW proof). When such standard systems are measured in practice, disappointment is usually great!

... Now we had only heard of this air-to-water heat pump, which is cheaper to purchase but is supposedly COSTING NOTHING anymore (i.e., in operation).

A flat lie. While a certain amount of environmental energy can be used with an air heat pump, compressors and evaporators require electricity, as does the additional heating element.
Nevertheless, an air heat pump can certainly be more advantageous than electric gas, provided the framework conditions are suitable.
The problem with the gas variant is the solar thermal system! However, that can also be avoided.

... For example, Viebrockhaus has this system in all houses. Even though Viebrockhaus is too expensive for us, we are now interested in this system.

I have completely different results available on a larger scale. Depending on the variant, different configurations are used, not only with this provider.
Here, I can only advise the utmost caution and under no circumstances to sign without independent advice/calculation.

... Would it be worth it?

There are no general statements for this, if they are to be reliable. This must be calculated based on the specific building and climate data as well as user behavior! Only with the results is it assessable which solution actually proves economical and sensible for the builder.

... And what is meant by this: HT/NT special tariffs of the local utility?

These are special tariffs for the supply of heat pumps.

Best regards

Hello,

what would be the conditions/information needed to choose the right heating system? We are very unsure about which system to decide on.

I cannot estimate the consumption yet. I can only say that our house will be about 240 sqm, we want KfW70, and that initially only three of us will move in. Of course, children may join in a few years.

Regards

Kati

Hello,

...what would be the conditions/information one would need to choose the right heating system? We are very uncertain about which system to decide on here.

These are especially the building data (geometry, used components [U-values], ventilation, building tightness...), 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 is then obtained in connection with the respective technical solution! Different variants can then be compared here. The results from the Energy Saving Ordinance/KfW certificates are, due to the standardized boundary conditions, generally not suitable for this. However, the building data can certainly be used from them!

...I cannot yet estimate the consumption.

Even "experts" have certain problems with that ;)

It always amazes me how carelessly construction contracts are signed with the resulting significant financial consequences. When I then look at such, partly botched systems, the builders give standard answers like:

"We were told that...."
- but there is nothing stated in the contract!
"If we had known that, we would have...."
- inform yourself beforehand and get external advice.
"Can't we still......"
- usually only corrections within certain limits are possible (depending on the individual case). Prevention is always better than cure!
"We assumed that a professional company would...."
Yes, sure, and it will certainly get warm too – only the consumption costs are significantly too high due to the lack of energy efficiency, and now?

I rarely indulge in general statements, but so much can be said in advance due to current circumstances: for example, an exhaust air heat pump as a base load heat generator does not belong in an Energy Saving Ordinance or KfW70 building, whereas an air heat pump can certainly be useful!

Equally surprising is how meticulously and in detail tiles, bathtubs, a dormer, room layout, etc. are chosen. The essential basics of efficient building services engineering (exact calculation/dimensioning), on the other hand, are ignored or not noticed at all. Almost every toad presented by the seller is swallowed.

Without reliable and verified consumption prognosis, I would not have a building constructed or bought!

Best regards