ᐅ Draining air conditioning condensate in a KfW55 energy-efficient new build

Hello community,

we are currently planning the construction of a new KfW55 single-family house with a heat pump and controlled ventilation system. We know that shading can effectively keep the heat outside, but in extreme weather and possibly due to careless children, we don’t want it to take weeks to get the heat out of the house again. Therefore, we want to install air conditioning units both on the upper floor and in the southwest-facing living area.

All air conditioning pipes are planned to run via the suspended ceiling in the guest room to the outdoor unit on the garage. The problematic part is the condensate drainage: For the unit on the upper floor, as well as the one in the ground floor guest room, we can route the condensate drain to the washbasin trap in the bathroom. For the unit in the ground floor living room, this is not easily achievable. We see the following options:

• Have the builder include a separate DN35 (1.4 inch) drain pipe in the floor slab, located in the wall between the living area and the guest room
• If connected to the wastewater system, we would additionally need a built-in trap (e.g., a climate trap from Dallmer)
• As far as I understand, connection to the rainwater drainage is not permitted
• Set up a small soakaway pit under the terrace: Would something like this work with our marly/clayey soil? Of course, it would be difficult to access for maintenance—how should something like this be implemented?
• Install a condensate pump and run the condensate through the guest room ceiling also to the washbasin in the bathroom
• Run the condensate hose directly through a core drill hole to the outside, meaning cutting through the wall between the living and guest room, then down and out

I actually find option 1.3 the most elegant, but the HVAC technician cannot guarantee that water will not back up and drip from the unit. He naturally prefers the classic option 3. What would you do? Where do you see the pros and cons?

Is the air conditioning really necessary? God knows! We will find out. Either way, we just want to find the best technical solution for the condensate drainage.

Thanks in advance

Best regards
Dash