Controlled residential ventilation - Yes or No?!

Hi everyone,

here is a little experience and opinion about [Kontrollierte-Wohnraumlüftung]:
We have been living in our little house with [Kontrollierte-Wohnraumlüftung] since the end of February and are totally enthusiastic about it.
I think the best proof of the good function of a [Kontrollierte-Wohnraumlüftung] is the following:
We have two dogs and they do "smell" like dogs (especially when it rains). Non-dog owners immediately noticed the dog smell in our old apartment.
Meanwhile, our visitors reported that you do not notice any odors in our house - no dog smells, no cooking smells, etc...

For us, the [Kontrollierte-Wohnraumlüftung] is clearly also a gain in comfort, because, for example, we don’t have to open the windows in the bathroom for ventilation directly after bathing/showering.
Our hygrometer usually shows around 80% humidity after the bath session, and after about 15 minutes the value settles again at 45%-50%.

From our point of view, the [Kontrollierte-Wohnraumlüftung] has clearly been a very sensible investment.

Cheers

Andy

Well. A system with many unreachable pipes inside the house might be an advantage for air exchange. However, I consider it more than likely that germs and bacteria settle in the piping over the years, which then spread throughout the house.
Moreover, such a system always creates a slight draft that might be absolutely unnoticeable to most people. But if someone is very sensitive to it, they will always find it disturbing.
As for mold formation, I think that a poorly insulated house (old building) is more prone to mold because moisture settles on cold exterior walls.
Everything has its advantages and disadvantages.

Regards

Hello,

Rather rare....

To prevent water vapor condensation in multi-layer components, the thermal resistance should increase from the inside to the outside (thermal insulation layer outside) and the vapor diffusion resistances should decrease. These conditions are met, for example, in the wall structure: interior plaster, sand-lime, solid bricks, mineral wool, air layer, façade panel (wall with ventilated façade). If the wall remains damp, which is particularly important to consider in new buildings, then water behind a waterproof or water-repellent outer layer, as can be the case with the thermal skin, can hardly escape by diffusion and the masonry will be damaged over a long time.[1]

[Source 1] Kur, Friedrich; Wohngifte, Handbook for healthy building and furnishings

Thanks to the planners at the green table in Brussels, a relic from the good old days; in the meantime, at least small ventilation flaps for windows are offered again – better than nothing at all.

It’s not that simple; in the evenings and nights the residents are usually at home and not all moisture is removed by ventilating twice – including the moisture from the morning bathroom visit.

In new buildings moisture inevitably occurs, even though many bricks are glued nowadays – not as much as before, but with the screed still enough water enters the house and an ETICS just doesn’t make it any easier. You can’t get around that.

Kind regards

Hello,

Regarding mold formation, I think that a poorly insulated house (old building) is more prone to mold because moisture settles on cold exterior walls.

Wrong thinking, quite the opposite is true - with few exceptions. It is the highly insulated houses with ETICS that have caused mold to flourish.

Kind regards

Hello,


Wrong thinking, exactly the opposite is true - with few exceptions. It was the highly thermally insulated houses with ETICS that caused mold to flourish

Kind regards

Sorry Bauexperte, but that is not entirely comprehensible to me. Basically, an ETICS increases the surface temperature on the exterior walls. In uninsulated old buildings, this is often a problem because condensation often forms in the corners on the exterior walls, which ultimately leads to mold growth. An ETICS raises the surface temperature so that mold can no longer form. Mold growth can of course occur if the residents do not ventilate regularly. But this has nothing to do with the ETICS, rather it is due to other measures that have been responsible for the now no longer occurring air exchange (new windows, doors). A wall itself does not breathe, so no air exchange takes place through the walls either.

Regards

Hello,

Sorry building expert, but I can't quite understand that.

To prevent mold formation, you first need to know under which conditions it develops. There are four factors that inevitably lead to mold formation when they occur together.

- First of all, there is humidity. If it is relatively high, that is an essential prerequisite. Experts give 65 percent humidity as a lower limit. Wood is a good base for mold if it has moisture content of more than 30 percent.

- The temperature also has to be right. The most problematic range is 18 to 25 degrees, i.e. the temperatures that normally prevail in apartments.

- Mold must have a food source. It feeds on cellulose. This can be found almost everywhere in apartments - in wallpaper, paste, plaster or paint.

- Finally, the pH value of the substrate must be roughly between four and seven.

If these conditions come together, mold formation almost inevitably occurs.

About 10 years ago, more than 18 months often passed from the first groundbreaking for a solid house until the owners moved in. During the construction phase, the house usually stood as a shell over the winter; the water in the building materials was supposed to “freeze out”. Today, however, a solid house is usually ready to move into after a maximum of 9 months. The incorporated water mostly does not evaporate completely – so the house contains more moisture than before.

Another familiar scenario: A house is renovated and insulated against heat loss. Where previously doors and windows were not completely airtight, now nothing passes through – no heat, but also no condensation. This then settles on the wall surfaces, on wallpaper and paint – a splendid basis for all kinds of molds.

A three-person household produces an average of ten liters of water vapor per day — mainly through cooking, showering and washing. In the past, the water vapor could escape through leaky spots at windows and doors or condense on single-pane windows. The ventilation was effectively built-in in the poorly insulated house.

Today it is different: Precisely the increasing energetic insulation of houses lets molds literally flourish and thus increases health risks. A known case: In old buildings, single-pane windows are replaced by insulated glazing without simultaneously insulating the walls. Consequence: The water vapor no longer condenses on the windows, but on the now coldest spots. These are often corners of exterior walls, concrete lintels above windows or radiator niches, where the walls are usually thinner. Mold forms on these so-called thermal bridges. Condensed water can also appear behind pieces of furniture or pictures located on exterior walls. Reason: The exterior wall cools down because warm air cannot circulate behind it.

In new buildings erected according to the current thermal protection standard and with ETICS, molds can spread if ventilated incorrectly. In massively built new buildings, much more ventilation is required in the first year anyway than normal, because the walls still contain moisture.

The only alternative to controlled living space ventilation: dry heating. For this, you must not only keep the radiators on, but additionally vent the humid air outside especially often. The magic word is shock ventilation. This means opening the windows wide, letting the indoor air escape within a few minutes, closing the windows again and ideally repeating this process several times a day.

By the way, it is helpful if windows with forced ventilation were chosen when building the likely well-insulated house. This cannot replace shock ventilation but significantly supports the effect.

Kind regards

The question now is which is the lesser evil: a poorly insulated exterior wall on which condensation settles, or a well-insulated wall (+ window), where you have to remove the indoor humidity by ventilating.
However, I am of the opinion that you do not have to ventilate a renovated house with new windows (with window rebate vents) more often than before the renovation.

Regards