Preliminary Energy Considerations for House Construction

Hello

My wife and I are currently planning the construction of a one-and-a-half-story single-family house. We have also already read extensively, so we basically already know very well what we want ... and what we don’t want. The only question that poses some problems for us is which heating option is best for us, especially because we read very contradictory statements on every point on the internet.

I will try to describe our starting point and what we would decide based on the current state of knowledge. I hope there is someone here who can give us a few tips and/or advice on this.

The house we have chosen is by default being built with a solar system on the roof (for hot water) and a gas condensing boiler. What we have definitely decided on is underfloor heating (supply temperature 35°).
Last week I had a consultation with the consumer advice center on this topic, and they recommended expanding the heating system to include an air-to-water heat pump and using the gas boiler as a fallback for very cold days. So the air heat pump as long as temperatures outside are above freezing, and heating with gas at subzero temperatures, since the efficiency of an air heat pump drops sharply below 0°. For the transitional period, they also recommended a fireplace, which is not a problem for us since my wife wants one anyway.

In addition to the described heating circuit, we would like to have automatic ventilation and exhaust. Based on what I know now, I would prefer the decentralized variant with heat recovery. On the one hand, the acquisition costs are lower than for a centralized system (and most likely also maintenance costs), and on the other hand, my uncle has a similar system in his house and could tell us nothing negative about it.

I don’t have the exact roof dimensions at hand right now, but the house has external dimensions of 9m x 10m and a 45° gable roof. According to my rough calculation we have about 65m² of space on one half of the roof. This led us to consider whether it would be sensible to use only about two-thirds of the area for solar thermal and the rest for photovoltaics. That way we could produce some of the electricity needed by the air heat pump ourselves.

Well, that’s all I can think of for now.

We are grateful for any advice, since I am quite sure that we have simply forgotten one or another point in our previous considerations. Moreover, there are surely users here who know more about such things than we do and also already have significantly more practical experience.

Best regards from the very sunny North!

Just very generally. Everything you install in heating and energy technology must eventually pay off. From an economic perspective, the installation of a particular system only makes sense if the savings achieved eventually exceed the acquisition and maintenance costs. However, this does not mean that from an ecological point of view it might not still be sensible to operate the system.

Now all that's missing is an oil and a pellet heating system. Then you have gathered everything possible in your house. But is that really sensible and what does the fun cost? Solar thermal + photovoltaic system + gas boiler + air heat pump + fireplace (water-bearing?) together are certainly not cheap and probably never pay off. Just get proper advice. As a driver, you probably don't drive: a convertible for the summer, a sedan for the winter, a sports car for speeding, and the station wagon for the family. That's how your heating planning sounds :rolleyes:

When I see that some photovoltaics span the entire roof, it must be that the system technology only pays off with a lot of surface area. It also costs, I believe, around 15000? Maybe even more.
For that, you don’t need solar anymore.. Solar seems to be the cheapest way for home construction companies to offer a house according to the 2009 Energy Saving Ordinance. That’s all it is. If alternatives are installed, then you could do without it, but I would definitely factor in a provision for it later.
A lot of technology also means quite a bit more space needed for accommodation. Such a technical room consumes quite a bit; in a standard house without a basement, the utility room could get tight.
Controlled residential ventilation is never wrong... I don’t know about decentralized, but that could also be 8000.
Chimney with fireplace around 10000.
Underfloor heating 5000.
And then two heating technologies.... wow.

I would rather treat myself to a wellness bathroom with one heating technology :)

Hello,

By default, the house we have chosen is built with a solar system on the roof (for hot water) and a gas condensing boiler. What we have definitely decided on is underfloor heating (flow temperature 35°).
Last week I had a consultation with the consumer advice center on this topic, and they recommended expanding the heating system with an air-to-water heat pump and using the gas boiler as a fallback for the very cold days. So air heat pump as long as there are still positive temperatures outside, and heating with gas at subzero temperatures, since the efficiency of an air heat pump rapidly decreases below 0°. For the transitional period, he also recommended a fireplace, which is not a problem for us since my wife wants one anyway.

Oh man – if this keeps going, I probably won’t send anyone to the consumer advice center anymore :confused:

In addition to the described heating circuit, we would like automatic ventilation and airing. Based on current knowledge, I would prefer the decentralized version with heat recovery. On the one hand, the acquisition costs are lower than with a central system (and most likely also the maintenance/servicing costs), and on the other hand, my uncle has a similar system in his house and could not report anything negative about it.

I don’t have the exact roof dimensions at hand right now, but the house has external dimensions of 9m x 10m and a 45° pitched roof. According to my rough calculation, we have about 65 m² of space on one half of the roof. This led us to consider whether it might make sense to use only about 2/3 of the area for solar thermal and the rest for photovoltaics. That way, part of the electricity needed by the air heat pump could be produced ourselves.

Before I would install this whole (nonsensical) system in the house in your place – do your financial resources even allow this? – I would switch to other systems instead! I don’t know why the energy specialist offered you this “belt-and-braces” system, but I assume it is his idea of complying with the Energy Saving Ordinance 2014.

If the framework conditions of the planned building project – including external ones – allow it, a gas condensing boiler with solar domestic hot water heating (alternatively the 15% rule instead of solar), proper insulation under the floor slab, and decentralized ventilation with heat recovery are usually sufficient to achieve a KfW 70 efficiency house. Gas is – by the way – amid the confusion of the current price developments not the worst choice either, since its consumption price will have a favorable effect in the medium term due to newly developed sources. The underfloor heating, which must be installed mandatorily, also allows renewable technologies to be connected later, after the lifespan of the gas condensing boiler. Every builder set up like this thus has the time to observe the current technologies regarding lifespan and everyday practicality.

To say that an air-to-water heat pump needs “belt and braces” is quite something! It is true that it is still not suitable for every building project; but it is also true that where a serious calculation is underlying it, it serves well! With technology, it is like with the stones for the house itself: not every technology is universally applicable for all building projects. We have customers who are more than satisfied with their air-to-water heat pumps; especially concerning maintenance costs.

Photovoltaics – here you probably missed the boat. At an earlier time – when modules were also more expensive – good money could be made with such systems. Today, this story looks quite different again in times of reduced subsidies. In my personal conviction, photovoltaics only make sense if there is very high self-consumption and the possibility of storage. Here the advantages and disadvantages of previously known storage media must be considered again; costs are not insignificant either, especially if it should not be a lead battery.

In short – find a serious energy consultant you trust and discuss the options for “your” house with him. I am very sure that after this conversation you will only shake your head at the proposals of the person mentioned at the beginning.

Rhenish greetings

In addition to the air-water heat pump, I have also had a wall outlet for a stainless steel chimney installed, in case it turns out that the heat pump is overwhelmed or too expensive. That is not expensive and you can basically retrofit an additional heater for the living areas in the form of a wood stove very easily and relatively inexpensively, if you actually need it.

I am rather critical about the photovoltaic system. Your roof area is relatively small and you also have to consider that usually only one half (and perhaps not even that completely) can be used. That means that only a small portion of the own consumption can be covered and feeding into the grid, as already mentioned, is no longer financially attractive.