Plus energy house with hydronic pellet stove + WWWP for cooling?

Hello building expert, thank you very much for your detailed post.

Prefab house in the sense of "all services from one source" or actually prefab house?

We are currently actually leaning towards a prefab house. However, the decision is not yet final. Based on the information so far, this option seems the most attractive to us.

Yes, why do you doubt the statement of an expert?

Quite simply, because I am not sure if he understood that it does not necessarily have to be an open fireplace with logs, but for us variants would also be conceivable that emit less heat directly into the room. And it seems there are quite a few options. So far, I simply lack the expertise to assess it. So how much heating energy is really released? How much heating energy is actually needed in a passive house?

At most in the range of 2°; you must not forget that this will cause condensation on tiles. It's like a free sliding course.

Until now, I understood that this can be avoided by appropriate regulation. The 2 degrees could possibly be enough. It depends on how strongly the house heats up. But I am increasingly getting the impression that maybe a conventional split air conditioning system would be better after all.

Ground source heat pump preferred:
Why?

Because from what we have read so far, this is the most efficient option. However, I am happy to be proven wrong. If, in the end, a normal air conditioner makes more sense, the heat pump is probably out anyway.

You "seem" not to have had a proper consultation yet, otherwise you would already know that your current planning overshoots the goal "reasonable" by far. "More" has never been good; just as little compressing technologies. 'Wastl' has left very good approaches for you here.

Well, I have already spoken to a few people in the model home park. But I always had the impression that they primarily want to sell me what they offer. That’s logical and not objectionable. A young gentleman who wanted to rush me because of the current interest rates, however, really crossed the line. Well, he was probably still new.

In my opinion, you should not focus solely on a KfW 55 subsidy; TEUR 100 sounds nice at first, no question. However, if I consider that the savings in energy costs from the Energy Saving Ordinance (or old KfW 70) to KfW 55 are marginal, I consider the use of required resources borderline; certainly uneconomical.

That’s exactly the question: Is it worthwhile? I would also like to calculate this myself. However, I am missing some important variables, e.g., how high the savings are with the different variants actually and what the real additional costs of the different variants are. I trust myself to consider the differences in subsidies, a few assumptions about the development of costs for electricity, gas, pellets, etc. I have found some calculations on the websites of some prefab house providers, but they also want to sell the houses, and unfortunately not all assumptions are disclosed.

Complete autonomy is not possible in our latitudes in NRW; 70% - with storage - is a realistic figure. But you don’t need to detour via KfW 40 Plus for that. One of our builders - we handed over the house in 2014 - recently proudly told me that his energy costs have settled at €10.00/month. He achieves this through a new building according to KfW 70 plus photovoltaics on the roof. I will meet him next week and have him give me a copy of the annual statements.

May I ask about the house's features? Square meters, roof, size of the solar system, storage, etc. Ten euros is quite a figure. The savings potential from KfW 40 compared to KfW 70 is apparently not that big anymore.

In short - you should ask yourself the question: "what do I want?" Is it about claiming subsidies - KfW 55 must be reached; is it about the best possible reduction of energy costs, other paths lead to Rome. If the thought of a possible resale of the property plays a role in your considerations, remember that potential buyers are not interested in the standard according to which your single-family house was built. They are only interested in the condition of the property, such as ongoing consumption costs.

I only want to claim the subsidies if it pays off in the end. So I can take the repayment grants, savings through the lower interest rate, and savings on energy costs and put them against the additional costs. But as written above, I currently lack the knowledge to estimate energy savings and additional costs.

If you are an expert, maybe you can shed some light on this?

Oh yes, and best regards from the Rhineland back to you.

Good day,

Hello Bauexperte, thank you very much for your detailed post.

You’re welcome

We are actually currently leaning towards a prefabricated house. But the decision has not yet been definitively made. According to the information so far, this option seems to be the most attractive to us.

Ok. Then you also know that if you will hopefully decide on a reputable provider, you will need an architect - the well-known providers have fixed cooperations. Otherwise, I can’t contribute much essence regarding prefabricated houses, as I belong to the conventional bricklayers.

How much heating energy is actually needed in a passive house?

In a genuine PH – not to be confused with a low-energy or plus-energy house – no heating system may be installed at all!

But I increasingly have the impression that maybe it should be a conventional split air conditioning system after all.

I am always in favor of neatly separating trades, just as I would never buy a washing machine with an integrated dryer

That’s logical and not reprehensible either.

Agreed. However, there are also good sources outside of company policy-colored information from which one can inform oneself; that was the aim of my question. There are increasingly good presentations at trade fairs; the VBZ, energy agencies as well as adult education centers offer good input. Construction diaries are also a good indicator of how much the sales strategy of providers actually plays out in real life.

That’s exactly the question: Is it worth it. I would also like to calculate it myself. However, I lack some important variables, e.g., how high the savings actually are with the different options and how high the actual additional costs of the various options are. I trust myself to take into account the differences in subsidies, a few assumptions about the cost development of electricity, gas, pellets, etc.

That can hardly be calculated, since your personal experience values from the new construction (which still has to be built) are missing. However, if you read the posts on the topic here in the forum, you will quickly find that the energy cost savings of KFW 55 compared to KFW 70 – and thus almost current energy saving regulation – are marginal.

If you do actually decide on a prefab house, the question of calculating possible additional costs/speculation on electricity prices, etc., in my opinion doesn’t apply to you anyway, since reputable providers offer KfW 55 as standard.

May I ask about the characteristics of the house? Square meters, roof, size of the solar system, storage, etc. 10 euros is already a nice figure. The savings potential of KfW40 compared to KfW70 is apparently no longer so big.

146.00 sqm living space on BP, gable roof 37°, built according to KfW 70, photovoltaic _without_ storage, is currently all I can offer you; with us, the calculation and installation of photovoltaics is outsourced to a specialist company – everyone does what they do best We have an appointment for a chat again next week, after which I will gladly provide the missing information.

Rhenish regards