ᐅ Split air conditioning system and mechanical ventilation with heat recovery

Hello everyone,

Does anyone have experience with a split air conditioning system combined with a central controlled residential ventilation system with heat recovery?

The main question is whether the controlled residential ventilation can distribute the cool air from the air conditioner and how well or poorly this works.

My idea: Because of the simplicity and short distances, I am considering a split air conditioning system with 2 indoor units.
The outdoor unit would be placed on the garage, and from there it is only about 50 cm (20 inches) through the wall into the bedroom upstairs and the living room downstairs. Power supply is also available. I want to avoid major effort and long duct runs to actively cool all rooms. The children’s rooms are not as easy to reach. It would be possible via an external duct on the outside wall, but I want to avoid that for aesthetic reasons.

The house was built in 2018 and exceeds the KfW 55 efficiency standard.
The primary energy demand is calculated at 42 kWh/m² (square meter) and the values from recent years confirm this.
We have 178 m² (1,914 square feet) of living space according to the living space ordinance and about 212 m² (2,282 square feet) of floor area. No basement and a gable roof are present, which explains the discrepancy.
Heating is provided by a ground-source heat pump with a water circuit, which is also equipped with a cooling function.
Cooling via the underfloor heating works satisfactorily and keeps the temperature around 24°C (75°F) even in midsummer.
However, it requires consistent shading and following recommendations. Once the heat has entered, it takes several days for the cooling system to lower the temperature again.
In 2022, we consumed 2,169 kWh of electricity and generated 9,408 kWh of heat for heating and domestic hot water.
The building is therefore comparatively efficient in terms of insulation.

We still want to get advice regarding the air conditioning. Both rooms are about 40 m² (430 square feet), and the question arises whether it makes sense to choose a more powerful air conditioner to have more cold air for distribution?

The controlled residential ventilation also supports this to some extent. In summer, it cools the outside air by a good 8°C (14°F).
The air volume flow is approximately 180 m³ (6,360 cubic feet) per hour on automatic setting.

Would the controlled residential ventilation noticeably distribute the cool air from the air conditioner and cool the other rooms, or would we rather get cooling zones within the house?

Thank you very much in advance.

No one has any experience?
No one has an air conditioning system and a controlled residential ventilation system?

A mechanical ventilation system with heat recovery does not distribute air very evenly. The heat transfer is quite low. However, I do believe that the temperatures will mostly even out, similar to how a heating system works. This is because the house is insulated only on the outside, not between rooms.

RotorMotor schrieb:

A mechanical ventilation system with heat recovery doesn’t distribute air very evenly. The heat transfer is quite limited.
However, I do believe the temperatures will mostly even out over time, similar to how it works with heating.
This is because the house is insulated only on the exterior, not between rooms.

If you heat only the ground floor with a wood stove, very little heat will reach the upper floor. It’s probably the same with an air conditioner, although there is a positive effect since warm air naturally rises.

Mechanical ventilation with heat recovery helps very little in this regard. Ultimately, you will need at least one air conditioning unit per floor.

Bookstar87 schrieb:

If you heat only the ground floor with a wood stove, hardly any warmth reaches the upper floor. It’s probably the same with air conditioning, although in this case the positive effect is that heat naturally rises.

The mechanical ventilation with heat recovery helps very little in this regard. Ultimately, you need at least one air conditioning unit per floor.

One air conditioning unit is planned per floor.
But I will report back.

Controlled residential ventilation does not actually distribute air. It extracts air and supplies fresh air.

Therefore, when cooling is running, the controlled residential ventilation should ideally be turned off or only operate at a low setting.