KfW 70 - 36er Ytong - Ventilation system

Whether double-shell with clinker is the best is hardly something one can say. It always depends on what one wants/needs to achieve and how. But it certainly counts as one of the more durable facades. It also doesn't always have to be more expensive. For me, clinker facades were priced about the same as ETICS.

Hello everyone,

we would like to build a single-family house with the following parameters:
- one and a half stories
- on a slab foundation
- approx. 125 sqm
- 36 cm Ytong brick (without additional insulation)
- mineral exterior plaster
- KfW 70
- triple-glazed windows
- Heating: gas/solar; underfloor heating throughout the house

Regarding a ventilation system, we cannot decide what would be appropriate.

Our options are
- no ventilation system (our builder believes we do not need a ventilation system)
- decentralized ventilation system
- decentralized ventilation system with heat recovery
- centralized ventilation system with heat recovery

We have read a lot in internet forums and the more we read, the more confused and uncertain we become...

Thank you very much for your support in advance!

Hello everyone,

As interesting as this discussion is, the original poster’s question was about something else. The thread is already on page 4 and very few have addressed the initial question.

Unfortunately, I cannot tell you much more here, but I notice that it often comes down to "convictions." Opinions on this topic vary. You will probably have to make the final decision according to your gut feeling and your budget.

Maybe this (almost simultaneously running) thread in this forum will help you:
https://www.hausbau-forum.de/threads/ventilatoren-fuer-feuchtraeume-und-abluftdunstabzugshaube.9077/

I'll write my standard response... because I am convinced... everything except a central controlled residential ventilation system with heat recovery in new buildings is nonsense...

With decentralized systems, you might save installation and procurement costs, but you have less comfort and higher operating costs afterwards...

Hello everyone,
I think it depends on the new building...
Here is a quote:
"
Functioning of a home ventilation system Through ventilation ducts, warm air is guided into the house by the home ventilation system. The energy of the waste heat is used to preheat the cold supply air. At the same time, the used air or the water vapor contained in the air is extracted. If the heat of the extracted air is not sufficient, it is additionally electrically reheated.
Disadvantages of a home ventilation system The disadvantages of a home ventilation system are therefore obvious: It is very expensive to purchase, must be thoroughly cleaned and maintained at regular intervals, and consumes additional energy due to operation and reheating. However, health hazards can also arise from a home ventilation system, because improperly executed heat exchangers, contaminated filters, as well as deposits in the ventilation shafts can lead, among other things, to contamination with bacteria, viruses, or legionella. The latter enter the breathing air and cause the life-threatening Legionnaires’ disease.
In summary: A home ventilation system is intended to correct the chain of building physical errors that have accumulated in the development of low-energy houses and passive houses. Ultimately, however, it is only another step into a dead end.
In low-energy houses that do not have a home ventilation system, the water vapor must be vented by shock ventilation several times daily, which causes a lot of heating energy to escape from the house."

The summary says it all... unfortunately, we can no longer do without ventilation systems in the low-energy and passive house sector, the houses are as tight as a plastic bag. I think less is sometimes maybe more... If I can provide the extra energy my building consumes regeneratively, for example via solar or wood, then that’s fine.

Sorry, but this doesn’t quite fit here, but when I see some people who want their house to consume almost no energy on the one hand... on the other hand, they drive cars with 250 hp.

With decentralized systems you might save on installation and procurement costs, but you have less comfort and higher operating costs etc. afterwards...

Higher operating costs?
I can't yet speak from lived experience, but can only refer to the consultation I had at the ventilation office.
Electricity consumption for
each pair of fans with heat recovery = 12 euros per year.
For our 170 sqm we need 3 pairs of fans with heat recovery (so a total of 6 fans) = 36 euros electricity per year (with continuous operation and 30 cubic meters of air exchange directly in the room)
The exhaust fans in the wet rooms only run shortly (based on humidity sensors and timers).
So I generously estimate a total of (exhaust fans and fans with heat recovery) 50 euros electricity per year.

Additionally, there is the filter replacement - once per year. Per filter about 1.50 euros (2.50 euros for pollen filters). Usually, the filters can be washed at least once in the washing machine - so often a filter replacement is only necessary after 2 years. But for simplicity's sake, if you count one filter replacement per year, that is 9 euros for 6 fans (15 euros for pollen filters).

As I said - I can only repeat the information from the consultation here. However, I have read similar figures about electricity costs from users online.

Other operating costs? I wouldn't know any at first.

I might be wrong @Mycraft, but you mentioned higher operating costs for the central system in the other thread.
That's why I am asking so precisely - I am interested in the differences, advantages and disadvantages of both systems (even though we have already decided on decentralized).

The electricity costs are comparable for both variants... the central system has only 2 fans... the decentralized one, on the other hand, has 10 or more... so overall you end up with similar values.

But with the decentralized system, you need more filters, have to clean the systems more often, because the heat exchangers etc. get clogged much faster than with central systems... Each fan also requires a separate condensate drain and must be installed absolutely airtight in the wall... and with 10 holes in the wall, the potential for errors is very high...

Furthermore, there is the factor that the fans also sometimes stop working... and not always within the warranty period... of course the seller says "They run forever" but that's not the case... and then you have to dig a little deeper into your pocket... etc.