Proper ventilation: tips and technology for home and apartment

In addition to construction defects, incorrect ventilation is the most common cause of mold. But constantly opening and closing windows by hand? Old school! Correct ventilation has long been taken over by clever technology in the house.

In order to save energy and heating costs, windows are now made denser and the insulation thicker. Since then, some have aired timidly. Consequence: Pollutants and moisture collect in the room. Excess moisture condenses in colder places, molds grow. This is unhealthy - especially for allergy sufferers.

Others still open the windows too long: the room cools down, cold wall surfaces make you shiver, you turn up the radiator valve. And instead of escaping, the moisture settles on cold window reveals and in outside corners.

Solution: Let it air

Isn't it a shame when expensive heat disappears through the open window? In the long run, it is cheaper to ventilate with automatic devices - instead of by hand and only by feeling. An automatic ventilation system brings fresh air into the house comfortably, automatically and in an energy-saving manner, and also keeps noise out. Filters stop pollen and dirt - good for allergy sufferers. There are various techniques for this:

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10 Show all Clever technology for good air

Dust-free air flows into the rooms through inconspicuous ventilation grilles in the wall or floor. The technical center is in the basement, for example. "Comfosystems" from Zehnder

Photo: manufacturer

Single fan for bathroom, kitchen or toilet. A sensor switches the device off when nothing is moving. Series 80 from Aereco

Photo: Aeroco

Wall-mounted heat exchanger, heats or cools, works quietly, a filter removes dust and pollen. Moisture is drained away: there is no longer any risk of mold. "Recovair 4" from Vaillant

Photo: manufacturer

Decentralized fans can be easily retrofitted. Sensors measure air humidity and CO ₂ content in the room and regulate the air supply accordingly. "ComfoAir 70" from Zehnder

Photo: manufacturer

Ventilates when the window is closed: ventilation system with heat recovery completely integrated in the window frame. Practical: no chisel work, etc. necessary. "SoleoAir" from Höhbauer

Photo: manufacturer

Window ventilation flap mounted at the top, also retrospectively, for many stop systems. "Gecco 3" from Gealan

Photo: manufacturer

Electronic drive tilts, closes and locks the window. Individually controllable or as part of a BUS system. "E-Tec Drive" from Roto

Photo: manufacturer

Ventilation is discreetly in the upper frame, is switched on at the push of a button. The window remains closed, but air still comes into the house. "VentoTherm" from Schüco

Photo: Schüco International KG

Open and close skylights using the smart home system depending on the level of sunlight, air humidity and CO ₂ content. Retrofitting possible. "Integra" from Velux

Photo: VELUX Deutschland GmbH

Central ventilation unit with heat pump: supply and exhaust air circulate separately - energy saving. "CWL-300 / -400 Excellent" from Wolf

Photo: manufacturer

1. Single devices

This inexpensive solution is suitable for individual rooms - such as bedrooms or bathrooms. They are installed in the window reveal, under the ledge or in the window profile. Sound-insulated fans draw air in and meter out used air. The most expensive use the heat of the exhaust air to temper the fresh air and filter it on top of that. Cost: from 400 euros.

2. Exhaust air system

Here, valves allow air to flow into the outer walls. A fan in the central exhaust pipe draws the used air from the kitchen or bathroom outside through poppet valves or grilles.

3. Ventilation system

With ventilation systems such as an exhaust air system, a decentralized supply or exhaust air system or decentralized living space ventilation, you have full control over fresh and exhaust air. It can be finely regulated, filters pollen and dust from the outside air, and temperates it in winter. Allergy sufferers can breathe easy. You don't have to wipe as much dust, you don't have to clear the flower pots, you don't have to be on the go when dark clouds announce rain, you don't have to check whether all the windows are closed when you leave the house. And those who live on a busy street are particularly grateful for a side effect: noise is also blocked out.

4. Recycling using a heat exchanger

Systems with counterflow plate heat exchangers recycle 80 percent heat. The used air is collected in a pipe network and passed through a heat exchanger on the way to the outside. There, it tempers the supply air, which is distributed through a second pipe string in the house. The heat is not only recycled once, but several times. Assuming a 10 percent loss, half of the original heat is still effective after 6 to 7 air changes, and a quarter after 13 air changes. This saves energy and pays off the better the house is insulated. The heat loss through the building envelope can be kept low by good insulation. A good time to retrofit a ventilation system: if you pack the house warm anyway.

Left picture: Comfort system that saves energy. Two pipe strings intersect in the heat exchanger. In it, the warm exhaust air heats up the cold fresh air.

Right picture: Saving solution. Exterior wall units bring in fresh air. The fan in the pipe run draws exhaust air from the bathroom and kitchen outside. Variant: The wall unit also blows the exhaust air out.

Photo: A. Schiebel

What does a ventilation system cost?

For a new single-family home, a central ventilation system costs around 2, 000 euros in material costs plus installation. In the old building, the structural conditions are very important. If the system runs all year round, it naturally consumes electricity.

Tips for manual ventilation

If you don't want to invest in new technology or live for rent, you still have to ventilate manually. Too much moisture is best ventilated outside with the warm air. Cold incoming fresh air is dry and can absorb water vapor again. Residential physicians advise that the room air should be completely replaced every two hours. If you only tilt the window (night ventilation), it takes 30 to 60 minutes. If you open the window fully (surge ventilation), you can do it in 5 to 10 minutes. It works best and quickest with cross ventilation (draft!): You open the window wide and one more opposite - and after 1 to 5 minutes you close both again. The colder it is outside, the quicker it is. Ventilating with the window tilted is convenient, but it's easy to forget to close the window. It costs! And attracts burglars! In old buildings with new windows, ventilation is required more often, since new windows are hermetically sealed for optimal thermal insulation.

How long to ventilate?

month	Ventilation time
December, January, February	4 to 6 minutes every 2 hours
March, November	8 to 10 minutes every 2 hours
April, October	every 2 hours 12 to 15 minutes
May, September	16 to 20 minutes every 2 hours
June July August	every 2 hours 25 to 30 minutes

Proper ventilation in the bathroom and kitchen

In wet rooms such as the bathroom and kitchen, you should open the window wide for 5 minutes immediately after water vapor has formed. The adjacent rooms should remain closed so that the moisture only escapes to the outside. Tipping would not suffice here because too little moisture can escape.

In multi-storey apartments, bathrooms are often windowless so that normal ventilation is not possible. Automatic deaerators are usually not sufficient to remove the moisture. The only help here is to open the door to the adjoining room - usually the hallway - and to carry out a “shock ventilation” there immediately and after each use of the shower or bath.

As soon as the moisture rises, the window opens automatically. Retrofit system for all Velux windows from MSR Electronic; approx. 220 euros

Photo: VELUX Deutschland GmbH

The optimal humidity

A 3-person household produces around 10 liters of water a day, which is released into the air in the form of water vapor. The hygrometer tells you how much water vapor is floating around - from the shower, bathtub and saucepan, from the sweating and breathing of humans, animals and plants. In a normally heated and ventilated apartment, the air has a moisture content of 40 to 60 percent - feel good values. Warm air absorbs more water vapor than cold: for example, up to 23 grams per cubic meter at 25 degrees.

The good old hygrometer is not only a useful accessory in the sauna. This should also be used to regularly check the air humidity in living rooms - especially in the bathroom and kitchen

/ likuzia