KfW 70 - 36er Ytong - Ventilation system

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

But with the decentralized one 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 sometimes stop working...and not always within the warranty period...of course the seller says "They last forever" but that’s not the case...and then you just have to dig a little deeper into your pocket...etc.

First of all - I think it’s good when such points are discussed calmly. This allows some tidying up of rumors and half-truths about central and decentralized systems.

As I already wrote, we need 6 fans with heat recovery for our future decentralized system (for about 170 sqm), which have a filter + 4 exhaust fans (which do not). Now I can’t estimate the price for the two filters of the central system, but for the 6 pieces we would incur a cost of between 9 and 15 euros per year (depending on the filter type). Incidentally, pollen filters can only be used once in the decentralized system, the others can also be washed.

The system can (but does not necessarily have to) be cleaned when changing filters – i.e. once a year (in case of heavily polluted outside air it might make sense to change filters and clean twice a year). The whole thing is relatively simple. Unscrew the cover, pull the fan unit out of the pipe, clean it, then push it back in, done. The pipe in which the fan sits is only as long as the wall is wide. The heat exchanger can be put in the dishwasher and rinsed (or bucket or wherever).

Condensate drain – our fans have a cover on the outside (ours will be made of stainless steel). The moist air is transported outside, condenses on the cover and drips off over a drip edge on the cover. This drip edge prevents the condensate from running down the house wall (which would be undesirable). Of the 5 systems installed in the ventilation office, 4 had such a cover WITH drip edge. Only one known manufacturer from Berlin did not include it. The cover is included in the price of the fans with heat recovery. For the exhaust fans we additionally ordered them.

The fan eventually stops working: Well – that can also happen with a central system, right? If it can’t be repaired (or repair is no longer worthwhile), the fan would have to be replaced. I think that with the central system higher costs could also arise.

Installation error potential: I give you 100% right there. This was one of the most important questions I had in the ventilation office. How must the fans be installed and above all – how do I avoid thermal bridges. Based on the explanation, I created a nice drawing that I will give to the installer (even if he then thinks I’m crazy). In addition, I plan to take a day off on the day of installation and supervise personally (even if the craftsman then gets annoyed).

The only thing that might cause more effort is that you have to walk with a ladder from fan to fan and climb up and down every time. With the central system, you change the filters in one place (unless you also have exhaust air filters – if I understood correctly). But if you want to clean the pipes in the central system, you also have to walk through the entire house, unscrew, dismantle, clean, reassemble (see your link in the other thread). Whether the effort is the same or higher, I cannot judge.

Yeah, that all sounds good... the drip edges are of course also one way... however, my observation has been that condensation etc. still occurs in the places where the facade has been penetrated due to rain and wind... with all systems, so of course with decentralized ones the facade needs to be cleaned more often...

As you yourself write, the entire unit can be cleaned during filter replacement... the "can" can definitely be replaced by must... because the diameter of the systems is relatively small and with continuous operation gets quite clogged within a year...

Of course a fan of the central system can also fail, but with decentralized systems it is much more likely, just because of the quantity and size... it's a simple calculation...

I am simply for central systems if you have space and possibilities... but I am of course primarily pro ventilation... so better decentralized than nothing at all... because that is the totally wrong way... at least in the age of plastic bag houses...

Yeah, that all sounds good... the drip edges are of course also one way... however, my observation has been that due to rain and wind, at the spots where the facade is penetrated, condensation etc. still occurs... with all systems, so with decentralized ones the facade naturally needs to be cleaned more often...

As you yourself write, the whole unit can be cleaned during filter replacement... the "can" can definitely be replaced by must... since the diameter of the systems is relatively small and gets quite clogged within a year of continuous operation...

Of course, a fan of the central system can also break down, but with decentralized systems it is much more likely, simply due to the quantity and size... it’s a simple calculation...

I am simply in favor of central systems if you have the space and possibilities... but I am of course primarily pro ventilation... so better decentralized than nothing at all... because that is the totally wrong way... at least in the age of plastic-bag houses...

The exterior covers are overall larger than the fan or penetration diameter. Thus, a certain amount of protection against wind, weather, and dirt is still provided. As mentioned – a large provider, with whom tradespeople often have distribution agreements, unfortunately does not offer these covers in their program.

I wrote "can be cleaned" because it is up to everyone. Personally, I am of the opinion: "If you invest so much money in building a house, it would be negligent as a homeowner not to give your property the necessary care and maintenance."

To what extent a decentralized or a central fan is more likely to fail, I cannot and do not want to assess. I simply have too little experience with this topic. However, I am of the opinion that with proper maintenance (see the paragraph above), the lifespan can generally be increased (aside from material weakness or manufacturing defects).

Otherwise, I am also an advocate for a ventilation system – with heat recovery. Of course, I first had to learn that despite the predicted 90% heat recovery (actually more like 80%), the system will never financially pay off purely in terms of costs. But I am already looking forward to the higher quality of life, and that cannot be quantified with money.

Hello,

Yeah, that all sounds good... the drip edges are of course also one way... however, my observation has been that due to rain and wind, condensate etc. still forms at the points where the facade has been broken through... with all systems, so of course with decentral ones the facade needs to be cleaned more often...

Regarding the "facade to be cleaned," I agree with f-pNo. You cannot assume that a single-family house – once built – requires no maintenance; the same applies to cladding facades. Furthermore, there are various providers for decentralized ventilation systems in this area.

As you yourself write, the entire unit can be cleaned during the filter change... the "can" can safely be replaced by must... since the diameter of the systems is quite small and they get pretty clogged up within a year of continuous operation...

Maybe you can get used to clearly emphasizing that you are merely expressing your assumptions?

Any homeowner can fairly easily clean the decentralized system; easier and less laborious than a central system. The system usually indicates independently that the filter needs to be changed. For that, the owner only has to remove the indoor cover, take out the filter, and insert a new or cleaned filter (by the way, the filters can be cleaned in the dishwasher). Then just inform the device that the filter has been replaced, and done. And even if this must be done once a year, that is not exactly a huge effort.

The ventilation ducts of a central system, on the other hand, require the presence of a maintenance technician who has a camera, vacuum device, and long brushes ready.

All in all, I would assume – adding all costs together – that the pure cleaning costs don't differ significantly between the two systems.

Of course, a fan of the central system can also give up the ghost, but with decentralized systems it is much more likely, just due to the quantity and size... it's a simple calculation...

In recent years, our builders have installed many ventilation systems; sometimes decentralized, sometimes central systems. Depending on preference and means. To none of the ventilation systems – neither of one nor the other systems – have I heard complaints about frequent filter changes or cleaning intervals. With reasonable advice – apart from the "wisdoms" of the internet – builders usually know well what to expect and when. If it were otherwise, my inbox would definitely flood, or at least there would be negative remarks on the internet regarding our way of building consultation and sales of single-family homes.

I am simply in favor of central systems if you have space and possibilities... but of course, I am primarily pro ventilation... so better decentralized than nothing at all... because that’s totally the wrong way... at least in the age of plastic bag houses...

Every system has – as always in life – advantages and disadvantages; the blissful and all-encompassing solution doesn’t exist in ventilation either. But I gladly agree with you on one thing – better a decentralized system than none at all; if the external parameters do not allow leaving out one or the other system.

You have decided on the central solution; fine. But your personal decision must not be used as a reason to negatively burden other systems based on assumptions.

Rhenish greetings

You have decided on the central solution; good. However, your personal decision must not be used as a reason to negatively impact other systems based on assumptions.

Rhenish greetings

With this thread and the thread, I think we have generally been able to clear up many speculations, assumptions, and prejudices (in my case regarding central ventilation and for regarding decentralized). Therefore, I found the discussion, after some initial difficulties, good and helpful. Everything is good.

https://www.hausbau-forum.de/threads/ventilatoren-fuer-feuchtraeume-und-abluftdunstabzugshaube.9077/

Hi
when I asked about the necessary cleaning of our central ventilation system, I was told it is not necessary. The supply air already has a filter, so the ducts behind remain clean. And every single intake opening for the exhaust air also has its own filter, so the exhaust ducts remain clean as well. Therefore, only the covers, which are easily accessible, need to be cleaned. Maintenance technicians with long brooms, cameras, etc. are not required.
Let's see if this actually works in reality. If not, I can also acquire the necessary equipment myself and get to work, it’s not rocket science, just a pure diligence task.