ᐅ Is Controlled Residential Ventilation Necessary with Thermo Walls?

We have received a house construction offer from Bien-Zenker. They use a Thermo Wall with a total thickness of 336mm (13 inches), consisting of a 200mm (8 inch) wooden frame structure and 300mm (12 inch) thermal insulation. The heat transfer coefficient is U = 0.142 W/m²K.

My husband is concerned that because of the wood in the wall, we might need a mechanical ventilation system with heat recovery to prevent mold. The heating system will be an air-to-water heat pump. However, we definitely do not want a mechanical ventilation system with heat recovery. If it turns out to be necessary for this wall construction, we would consider choosing a different builder.

What do you think?

Thank you very much and Merry Christmas!

Hello Anni,

anni0207 schrieb:
My husband is worried that because of the wood in the wall, we will also need a mechanical ventilation system to prevent mold. The heating system is an air-to-water heat pump. However, we definitely do not want a mechanical ventilation system. But if this wall requires it, we would choose a different provider.

I have been working in this industry for quite some time, and you can trust me when I say I initially had a hard time accepting the idea of “holes” in the wall.

Today, houses from reputable builders—regardless of the construction method or wall thickness—are built so airtight that it would be almost negligent not to have controlled ventilation. Even if one of you is home all day, experience shows that airing out by simply opening the windows is not enough to remove the moisture present from the construction, especially during the first six months. You can easily imagine what can happen if both of you are away at work during the day...

There are excellent providers of ventilation systems on the German market, all fully certified and reliable; the cost of the system is a good investment. Personally—even though I build monolithic structures—I will no longer sell a house without a ventilation system unless the client explicitly releases me in writing after I have informed them of the risks. The recent results of the blower door tests in our houses have made me reconsider.

Merry Christmas

Hello,

anni0207 schrieb:
... But we absolutely do not want a mechanical ventilation system with heat recovery. However, if it is required for this wall, we would choose a different provider...

A mechanical ventilation system with heat recovery offers more comfort but is neither mandatory nor always strictly necessary! The fear of mold drives the market quite well and generates additional sales for providers. To avoid all potential liabilities, it has become common practice to have customers sign a risk acknowledgment form. This often leads to the mechanical ventilation system becoming part of the contract for many customers.
Each case should be considered individually. In addition to the wall construction, location and user behavior play a major role. I have developed a checklist to assess whether a mechanical ventilation system is necessary. While I plan heating and ventilation systems and welcome every project, I recommend ventilation systems only where they are truly needed, unless they are desired purely for comfort reasons! Especially with timber frame construction, the construction-related moisture exposure is significantly lower compared to solid construction, so there is relief here as well.

Best regards

@ Euro: Thank you very much.

For health reasons, I am not allowed to install a mechanical ventilation system with heat recovery. I have severe eye problems, so my ophthalmologist strongly advised against it.

Therefore, we are looking for a construction method that does not require mechanical ventilation and with normal ventilation habits (opening windows several times a day for brief airing, as one has been used to since childhood) still prevents mold growth.

Hello anni207,

Bien-Zenker offers a wall system with vital storage bricks that are supposed to regulate humidity.

Since it is now difficult to find a provider that delivers an energy-efficient house without a controlled mechanical ventilation system due to DIN 1946, this wall system could be an alternative, as the controlled ventilation can be turned off.

However, I would find that too risky.

The statement that controlled mechanical ventilation should be avoided because of an eye disease is new to me.

Perhaps the ophthalmologist is confusing controlled mechanical ventilation with a standing fan.

There is absolutely no feeling of drafts in the house, due to the massive volume of air inside compared to the air exchange from the controlled mechanical ventilation.

Additionally, the air is filtered.

Regards

AxelF

Hello Axel,
thank you very much for your reply.

I have been in several houses with mechanical ventilation with heat recovery myself, and you can clearly feel the airflow!