ᐅ Ventilation System – General Questions about Ventilation and Maintenance

1) We are building our semi-detached house (about 120 m² (1,290 sq ft) with a basement, ground floor, first floor, and attic) following the 2016 energy saving regulations only, and now I’m a bit unsure whether we need a ventilation system since modern houses are so airtight. Our current ventilation routine is, I think, quite typical:

• Bedrooms are aired for about 10 minutes shortly after getting up and for around 15 minutes before going to bed
• Bathroom ventilation after showering or bathing
• Living room with open kitchen aired during the day as needed

Is this ventilation sufficient, or will a tight house like this inevitably lead to mold?

2) If we decide on a (central) ventilation system: how does maintenance and cleaning work? Our future house has the ground floor, first floor, and attic with rooms that need ventilation. If we place the system in the basement, there will be many meters of ductwork. How do you keep those ducts clean? I don’t want the system to constantly blow deposits or mold into the rooms after a few years…

3) If I understand correctly, the air between rooms with exhaust air and those supplying fresh air is balanced through door gaps. Doesn’t that create a rather strong airflow? Unfortunately, my wife is very sensitive to that.

junge_familie schrieb:
1) We are building our semi-detached house (around 120 sq m with basement, ground floor, first floor, attic) to meet the 2016 energy saving regulation only, and now I’m unsure whether we need a ventilation system since modern houses are so airtight. Our current ventilation habits are, I think, quite typical:

• Bedrooms are ventilated in the morning for about 10 minutes and in the evening before going to bed for about 15 minutes
• Bathroom after showering/bathing
• Living room with open kitchen during the day as needed

Is this ventilation enough, or will it inevitably lead to mold in an airtight house?

2) If we decide on a (central) ventilation system: how about maintenance and cleaning? Our future house has a ground floor, first floor, and attic with rooms to be ventilated. If we install the system in the basement, the ductwork will be quite long. How do you keep it clean? I don’t want the system to blow deposits or mold into the rooms after a few years...

3) If I understand correctly, the air balance between rooms with exhaust air and those with fresh air is achieved through the gap under the doors. Doesn’t that cause quite a strong draft? Unfortunately, my wife is very sensitive to that.

Regarding 1.

We were told that ventilating properly 4–5 times a day keeps you on the safe side. That includes at midday – which can be difficult when working full time.

Regarding 2.

The system should get a fresh filter once a year – apparently that can be done yourself. I plan to watch the technician closely the first time and then handle it myself going forward.

Regarding 3.

You only feel a draft directly under the air outlet. When sitting right below it (we have one directly above the sofa), you hardly notice anything anymore.

We still haven’t opened a window yet (moving in at the end of October).

Good luck

A friend of mine recently built a new house to KfW55 standards. It does not have a mechanical ventilation system. The energy consultant created a ventilation plan and recommends airing out the entire house four times a day.

In any case, make sure to install a mechanical ventilation system with heat recovery. There are also systems available with geothermal heat exchangers.

Regarding maintenance: The exhaust vents in the rooms should be equipped with filters. These filters need to be replaced as necessary.

For the system itself, the main filters should be vacuumed every 3 months and replaced once a year depending on the level of dirt accumulation.

The heat exchanger inside the unit should be cleaned every 3 to 5 years, and the condensate drain should be checked and cleaned if needed once a year.

We have seen numerous reports where mold developed due to the absence of mechanical ventilation with heat recovery. The problem is that spores are already present in the building before any visible spots appear.

When the system is correctly installed and adjusted, there is no draft or noise disturbance.