Meaningful energy concept for new Kfw70 construction without oil or gas

How does this unusual constellation come about? Why don’t you have the hot water prepared by the more efficient geothermal heat pump as well?

For underfloor heating, the geothermal heat pump only has to heat the water to an estimated 30 degrees (is that about right? I don’t have the flow temperature exactly in mind), for the hot water demand when showering and so on, we like to have 54 degrees in the 270-liter water tank. On the one hand, the enormous additional effort for the geothermal heat pump to power the hot water to the high temperature is inefficient (for your information: the electric auxiliary heating is switched off on both devices, we don’t want to heat with electricity but only operate the devices with electricity) on the other hand, why should the geothermal heat pump operate outside its efficient working range into a less efficient area to power more heat when 30 degrees are sufficient for the underfloor heating?

On the other hand, we only have "just" 48 sqm of surface collectors (8 mats each 1.0 x 6.0 m laid out on an area of 6x13 m at 1.50 m depth with corresponding spacing), which means 1. far less earthworks and therefore costs, 2. we remain much more flexible regarding the garden area in terms of construction and planting, and 3. a deep drilling would not be an option for us.

In addition, this way the ground can regenerate well for the geothermal heat in summer.

The air-to-water heat pump costs about 2400 euros, can be placed flexibly (does not have to be in the same room as the geothermal heat pump) and, as I already wrote, it efficiently! uses the waste heat from the heating circuit distributor and the condenser dryer (have you ever been in a room where such a dryer is running? You know what kind of heat bomb that is?). In our utility room, we can therefore 1. safely store food, 2. safely set the feeding bowls for the two cats without the wet food overheating and going bad / making the cats sick / attracting unnecessary flies, 3. where else should the "sudden" heat of the dryer that arises during the day when no one is home go? Outside? That would be inefficient!

And speaking of efficiency, the air-to-water heat pump uses 0.2 KW per hour when we shower in the morning (currently 2 adults as the children are still small and tend to bathe in the evening), the device runs for about 2 hours, if bathing was done in the evening, about an hour longer, the dryer runs about 2 hours…

Our heating engineer has been selling this package all along, we first looked at it in 2 houses as references because we were initially concerned about the relatively high noise level of the air compressor.
Acquisition costs including earthworks/installation, etc., were significantly cheaper for the package; I can check the exact cost savings again. And the operating costs are also cheaper than installations with pure geothermal or pure air heat (which he also installs at customer request, as not everyone wants/can/wants to set up a second device).

The whole thing has been running for several years now, and top quality!

By the way, in summer the room has an absolutely cool temperature to also store salads etc. there that you prepared during the day for a barbecue, for example.

By the way: brine heat pump AND air heat pump... - how is that? Also, heating circuit distributors should be insulated. In a semi-modern utility room there is no waste heat anymore - except from the clothes dryer.
Best regards

To clarify again: THE heating circuit distributor is located IN the utility room, no matter which room I am heating EVERY pipe in the floor starts in the utility room and thus generates heat from the floor, practically indirect geothermal heat.
Behind the distributor is the guest bathroom, in which not all pipes could have run, and since you can’t press the pipes stress-free at a 90-degree angle onto/into the floor over just 10 cm (width of the distributor) in order to let them run practically out of the wall, the pipes run in a relaxed curve out of the distributor into the utility room floor and out again towards the door… I have attached one of the preliminary floor plans (red bar is the distributor).

PS: Freezer and pump unit of the rainwater system also generate waste heat, not much but still, the device for the central vacuum system is also hanging there but I think it doesn’t generate much.

For the underfloor heating, the ground source heat pump only has to heat the water up to approximately 30 degrees (is that about right? I don't have the exact flow temperature in mind), for the hot water demand when showering and so on we need about 54 degrees in the 270-liter water tank. On the one hand, the enormous additional effort for the ground source heat pump to power the hot water to the high temperature is inefficient (for your information: the electric auxiliary heater is switched off on both devices, we don't want to heat with electricity but only operate the devices with electricity) on the other hand, why should the ground source heat pump work outside its efficient operating range into a less efficient range to power more heat when 30 degrees are sufficient for underfloor heating?

The ground source heat pump should also be able to alternately heat hot water/heating water. Right now, the air source heat pump is running in an inefficient mode.

On the other hand, we only have "48 sqm of surface collectors" (8 mats 1.0 x 6.0 m laid out on an area of 6x13 m at a depth of 1.50 m with appropriate spacing) which means 1. significantly less earthworks and thus cost, 2. we remain much more flexible regarding the garden area in terms of construction and planting, and 3. a deep drilling would not be an option for us.

Of course, if you simply don't have space for collectors, that's another matter. Purely from a cost perspective, you probably could have put the money for the air source heat pump into the ground collectors.

In addition, the ground for the geothermal energy can regenerate well in summer.

The air/water heat pump costs about 2400 euros, can be flexibly installed (does not have to be in the same room as the ground source heat pump) and, as I have already written, it efficiently uses the waste heat from the heating circuit distributor and the condensing dryer (ever entered a room where such a dryer is running? Do you know what kind of intense heat there is?) In our utility room we can therefore 1. store food safely, 2. place the two cats’ feeding bowls safely without the wet food overheating and spoiling / the cats getting sick / or unnecessarily attracting flies, 3. where else should the "sudden" heat from the dryer go during the day when no one is at home? Outside? That would be inefficient!

Yes, I know what kind of heat is generated there. I use a condensing dryer myself. But even without a waste water heat pump, the energy is not lost since it stays within the building envelope.

And speaking of efficiency, the air/water heat pump operates at 0.2 kW per hour, when we shower in the morning (currently 2 adults as the children are still small and tend to bathe in the evenings) the device runs for about 2 hours, if there was bathing in the evening, it runs about an hour longer, the dryer runs about 2 hours…

I strongly assume the ground source heat pump does this more efficiently due to the actually better possible seasonal performance factor.

Our heating technician has been selling this package forever,

I believe that, he also profits from the purchase costs.

And the operating costs are also cheaper than installations with pure geothermal or pure air source heat

I doubt the operating costs are cheaper than pure geothermal, probably cheaper than pure air source heat.

The whole thing has been running for several years now and working great!

I believe that.

In general, this concept might work. If the property no longer allows for collectors, that might also be a solution, but in terms of acquisition/operating costs certainly not the ultimate. And if you say your heating engineer has been selling this concept "forever," then that is certainly not entirely without interest...

I have to intervene here. I don't quite understand why you can reduce the collector area so drastically, unless you are putting more energy in the form of electricity or other energy sources (e.g. fireplace). For 125m² of living space, we have an estimated ratio of collector area to living space area of 1:1. You want to get energy for about 160m² of living space from 48m² or 78m². The heat for water and heating is primarily generated by geothermal energy both in your case and in ours. Additionally, there is the heat energy loss from the condensation dryer in both your case and ours. The only advantage for you is that you use the ineffective heat from the utility room and the geothermal heat pump may operate in somewhat more efficient areas. However, this does not explain the huge ratio difference of the collector area.

Good, if everyone offers a different concept, it can no longer really be compared anyway. The best way is to select the most suitable system concept based on the calculated heating load and have several companies offer it to you.

Do you want to, or can't you understand it? 3 heating companies offered, and all 3 companies offered exactly the same, namely gas with solar, geothermal, geothermal with air-water heat pump, district heating...

Company 1 offered via the carpenter, Company 2 and 3 created their offers exactly based on Company 1's offer...

And that can't be compared? Then nobody needs to inquire anywhere and no company needs to write offers anymore...

I have to jump in here. I don't quite understand why you can drastically reduce the collector area like that, unless you are using more energy in the form of electricity or other energy sources (e.g. fireplace). We have, with 125m² of living space, an estimated ratio of collector area to living space area of 1:1. You want to get energy for about 160m² of living space from 48m² or 78m².

The heat for water and heating is primarily generated by geothermal energy both in your case and ours. In addition, there is the heat energy loss from the condensation dryer both for you and for us. The only advantage you have is that you use the ineffective heat from the utility room and the geothermal heat pump perhaps operates in somewhat more effective areas. But that does not explain the huge ratio difference of the collector area.

I can only tell you what is installed with us or others in our region...Vaillant geoTHERM VWS brine-water heat pump 61/3 in conjunction with Vaillant compact collector VWZ KK8 (8 collector mats 6x1 m)...For hot water a Vaillant geoTHERM VWL BM/2

Excerpt from Vaillant: "Ground-coupled brine-water heat pumps extract around 75% of the produced heating energy from the ground. Compact collectors offer a possibility to tap the heat source earth for small plot areas and when using low-temperature heating systems. Compact collectors consist of several prefabricated collector mats laid horizontally in the ground approximately 20 cm below the frost line (about 1.2 to 1.5 m deep). The compact collector is flowed through by a water-antifreeze mixture (brine). Due to their hydraulic properties, compact collectors are not suitable for high-temperature applications (e.g. radiator systems or high hot water demand) compared to ground collectors and geothermal probes."

Perhaps the term "low-temperature heating system" is the decisive factor here... I don't know your heating principle, I only know that there was always talk of underfloor heating, probably due to the high insulation standard as a timber frame construction as a KFW70 house with controlled residential ventilation with heat recovery) we generally like it nice and cozy warm, but we don't need much heating (by the way, the electric additional heating is turned off)