ᐅ Cooling with a heat pump through underfloor heating?

We have both an air-to-water heat pump for heating and an air conditioning system. The HVAC technician explained during the briefing that the air conditioning system is basically a heat pump as well—just like the heating system. However, it uses three split units mounted on the walls that circulate air within the rooms, rather than distributing it through pipes in the floor.

We chose the air conditioning system instead of the special cooling function of the air-to-water heat pump. From most sources I’ve heard, on really hot days when cooling is needed, the 2-3°C (4-5°F) temperature reduction achievable through the air-to-water heat pump and underfloor heating pipes is often not enough. It was important to us to have effective cooling, especially on days above 35°C (95°F), because if it’s 37°C (99°F) outside, I don’t want the temperature indoors to be around 34°C (93°F).

Absolute priority number one should be to design a house in a way that prevents overheating from the start. It seems crazy to knowingly run into this problem and then install an air conditioning system.
If a heat pump can only cool by 2-3°C (4-5°F) and that is not enough, in my view, this is a major planning error.

You mean the popular large window fronts that are then mostly darkened with roller shutters, blinds, or similar for most of the time?

I’d rather use air conditioning and keep the natural light and view as they were intended.

Hangman schrieb:

If a heat pump can only cool by 2-3°C (4-5°F) and that is not sufficient, in my opinion this indicates a serious planning error.

Objection: Looking back at the development over recent years, I believe the planning mistake was building in Germany. In Sweden, for example, summers are not as hot ;-)
At some point, heat will get into every house—planning or not. And then you end up with the problem that not only is the cold kept outside, but also the heat is trapped inside. At that point, only an air conditioning system helps.

Mycraft schrieb:

Since the attic can reach sauna-like temperatures in the summer, the COP drops drastically and the system consumes more electricity than necessary. So, if you want an efficient system, it either needs to be installed outside or the heat exchanger must be able to be freely ventilated with outside air in the attic.

Yes, that sounds reasonable.
Since we’re still planning to renovate the facade, it might be a good idea to have conduit pipes installed during that work, so we have the option later on. The bedrooms are on the upper floor. The final solution hasn’t been decided yet. How large should the conduit pipes be?
It could also be a ventilation system installed in the attic to help with cooling in the summer.
Should I open a new thread for this?

@kati1337

The only right decision. With today’s (intended) construction methods, without relying on special features.

Hangman schrieb:

The absolute top priority should be to design a house so that overheating doesn’t occur in the first place. It’s crazy to knowingly stumble into this problem and then install air conditioning.

Not everyone wants to live in a bunker. The focus of all these regulations (energy saving regulations and the like) is on the winter months to save heating energy and to avoid the dreaded CO2 emissions. However, this effect doesn’t reverse in summer (how could it?), so the heat gains remain inside.

Hangman schrieb:

If a heat pump can only cool by 2-3°C (4-5°F) and that is not enough, in my view there is a major planning error.

No, there is no planning error. That is what is possible without additional measures and only using the promoted underfloor heating cooling system, regardless of what the general contractor/developer/agent/manufacturer says. Purely from a physics standpoint.

Schimi1791 schrieb:

How big should the empty conduits be?

DN50 (diameter nominal 50 mm) is enough for each indoor unit. But you also have to consider the condensate drain. So if you’re already planning, you need to provide a bit more than just empty conduits.