ᐅ Renovation to KfW 85/70 Standard: Ventilation Including Cooling

Hello everyone,

We are planning to renovate an old building with 3 residential units to meet KFW House 85 standards, and possibly even KFW House 70.
We are looking for a solution that brings fresh air into the house and provides active cooling during the summer.
So far, the idea for heating is to install a heat pump supported by photovoltaic panels and distribute the heat through underfloor heating.

Does anyone have experience or recommendations for ventilation systems with active cooling functions?
An app control would also be great, although I have seen that the app from, for example, Nilan, tends to have poor reviews in the app store.

Thank you very much!

Your heat pump might already include a cooling function from the factory or can be upgraded with one relatively affordably. Within certain limits, this works quite well through underfloor heating and provides a noticeable improvement.

If you want to use cooling through the ventilation system as well, you first need to install insulated/conditioned ventilation ducts to prevent condensation. These are more expensive than standard mechanical ventilation ducts, but there are now good solutions available (e.g., Zehnder ComfoTube Therm). Zehnder also offers mechanical ventilation units with cooling, such as the ComfoClime Cool – however, you need to check how the sizing fits your house, and for three residential units, you also have to consider how individually controllable and adjustable the system must be.

Keep in mind that the cooling functions, at least when considered alone, are not comparable to a proper air conditioning system – 30 degrees Celsius (86°F) outside and 18 degrees Celsius (64°F) inside is not achievable, especially if you don’t also have effective shading. However, if you use both methods simultaneously (i.e., a heat pump with underfloor heating and mechanical ventilation), you can cool effectively in summer – provided there is a smart central control system that allows both units to work together efficiently.

Mechanical ventilation systems with heat recovery that can also actively provide cooling do exist. The challenge is more that there are three apartments with three different requirements. Then there is the issue of fire safety and sound insulation, which are prime conditions for things to go wrong. These systems also require a minimum airflow volume to deliver acceptable performance.

I’m not sure about the size of the apartments, but intuitively, I would consider decentralized ventilation. And if cooling is desired, then small split air conditioning units (such as fire and ice systems) might be the way to go.