ᐅ How to Plan a Heat Pump Heating System in a New Build?

andimann schrieb:

This results in significantly longer pipe lengths and therefore higher flow resistance that your pump needs to overcome. Additionally, you may face considerably higher initial costs due to more heating circuits, etc.

Limit the maximum length to 80 meters (260 feet). Naturally, more heating circuits mean a more expensive manifold and pump—well, perhaps a stronger pump. But these are one-time costs in the low hundreds of euros range.

Tolentino has already covered everything about the buffer tank, and the best buffer is the screed itself since it involves tons of material.

Karlsson schrieb:

Thank you very much for the valuable tips.

Not every tip is worth gold, even if it is given with confidence and no ill intent.

Offtopic schrieb:

Example: Supply temperature maximum 25–28

A supply temperature of 25°C (77°F) is not practical and I have not seen it implemented so far. Whether the supply temperature at design outdoor temperature (NAT, approx. -10 to -12°C (14 to 10°F)) is 30°C (86°F) or 35°C (95°F) does not make a big difference in electricity consumption – the savings from the lower temperature difference are just a few percent.
Lowering the supply temperature below a certain value, however, brings other advantages.
At 35°C (95°F) supply temperature, the floor surface temperature is around 27°C (81°F), with, for example, a room temperature of 22°C (72°F). If the sun shines and the room warms up to 24°C (75°F), you still have a significant heat output to the room and need an individual room controller that can shut off the respective heating circuits. This is the classic underfloor heating with conventional individual room control.
If the supply temperature is lowered to 30°C (86°F), the floor surface temperature is about 24°C (75°F). If you now have additional heat gains in the room from the sun or other sources, you automatically have little to no heat output to the room from the floor above 24°C (75°F). You no longer need individual room control; the room temperature regulates itself automatically depending on the length of the pipes installed and the flow rate.
If you want to reach 23°C (73°F) or 24°C (75°F) in the bathroom, you need this supply temperature of 30°C (86°F); otherwise, you will not be able to warm the room sufficiently. This is especially true in bathrooms, where there is higher air exchange. With 25°C (77°F) you will not get very far. Maybe 28°C (82°F) is possible, but 30°C (86°F) works just as well, and 28°C offers no added benefit.
At 30°C (86°F), rooms that are used less often or bedrooms can of course be equipped with individual room control, but at least half of the rooms should remain "uncontrolled". Desired temperatures are set once centrally via hydraulic and thermal balancing and can be finely adjusted in secondary rooms as needed.

Offtopic schrieb:

Pipe spacing nowhere more than 10cm, walls mandatory in bathroom, max pipe length 80m

Karlsson schrieb:

Is a smaller pipe spacing necessary so that the heating operates with a lower supply temperature? Have I understood this correctly?

Pipe spacing can be larger than 10 cm (4 inches), and walls are not mandatory in the bathroom either. What matters is the result of the heat load calculation. First calculate, then plan pipe lengths; from this, pipe spacing and whether walls should be covered are derived. The goal should be a low supply temperature at design conditions — ideally below 30°C (86°F) — to avoid the need for individual room control without problems.
Regarding pipe length, considering flow and pressure loss, I would not exceed 80 m (260 ft), but also avoid large variations. Balancing becomes more difficult the bigger the differences between heating circuits are.

Offtopic schrieb:

And with 7.5 kW you can heat a 300 m² house on the Swabian Alb to 25 degrees. So way too big.

Offtopic schrieb:

For a 150 m² house you end up around 4 kW.

These statements contradict each other. According to the 2023 building energy regulations, for a 150 m² house, you get roughly 35–50 W/m² (depending on volume, location, and window area). That corresponds to a heating load of about 5–7.5 kW. The 7.5 kW is rather the upper limit, but the questioner did not specify if they are building to the KfW40 standard. More precise information comes from the heat load calculation and room-by-room heat load calculations, which absolutely must be done. Otherwise, the underfloor heating cannot be properly designed, and the heat pump size should not be determined solely by floor area.

Offtopic schrieb:

Regarding the buffer, I would base it on the type of bathtub and how long you shower. We have 300 liters for four people and mother-in-law in the granny flat. Water has never run out unless I messed with the buffer 🙂

To avoid misunderstandings: A buffer tank is for space heating, while a hot water tank is used for filling the bathtub. The first, as already mentioned, should ideally be completely avoided; the latter should be chosen with a large heat exchanger surface area (>3 m² (32 ft²)). 200–300 liters (53–79 gallons), depending on the number of bathtubs.

Offtopic schrieb:

He just wants it cozy and fast, but you will pay the price with your electricity in the future, and it will not get cheaper.

Your rough generalization cannot be confirmed. In my experience, there are uninformed people, engaged people, and the ones you described. They are roughly one third each.

It is clear that I need the heating load calculation, and I will request it now. I will then come back here with the results, and perhaps you might have some additional tips.