ᐅ Advantages and Disadvantages of Different Ventilation Systems

Hello everyone,
we are considering building a house and are currently having initial discussions with various providers. So far, we have spoken with three companies, and each offer includes a different ventilation concept:

Danwood: Central ventilation system with heat recovery

Heinz von Heiden: Central exhaust system with passive air supply without heat recovery (air is actively extracted outdoors via fans in the bathroom, kitchen, and utility room; in other rooms, air is passively drawn in through corresponding openings)

Scanhaus Marlow: Standard equipment only includes window frame ventilation. For an additional cost, a decentralized ventilation system with heat recovery is available.

At the moment, we are quite unsure about the advantages and disadvantages of the different systems and do not really know which direction to take. Therefore, we would appreciate expert feedback.

Specifically, the following questions arise for us:

What is the noise level like with the different systems? Especially with the decentralized system, I wonder how noticeable the fans are, since they are installed in every wall. I imagine it could be quite unpleasant, especially in the bedroom, if there is a constant humming or buzzing sound.

How significant is the impact of heat recovery? The system from Heinz von Heiden lacks this entirely. Does heat recovery noticeably affect heating costs, or can it be considered negligible in a new build?

Are there potential hygiene issues with central systems after several years? These systems have relatively long ducts throughout the house that cannot be easily cleaned if any dirt or mold develops.

Is it possible to install filters for pollen or even activated carbon filters in decentralized systems? Or is this feature exclusive to central systems?

How would you assess the fact that Scanhaus Marlow only installs window frame ventilators as standard? According to their advisor, ventilating twice a day should be sufficient to prevent mold issues. However, I am rather skeptical after reading up on the topic and tend to favor building with a ventilation system.

Olypen01 schrieb:

How is the noise level with the different systems?

Windows: inaudible, but outside noise is present
Decentralized: depending on the system, from not audible at all to slightly audible (also depends on your perception)
Centralized: usually inaudible, only slight noise at higher output
==> all options work well in terms of noise levels

Olypen01 schrieb:

How noticeable is heat recovery? The system from Heinz von Heiden completely lacks it. Does this significantly affect heating costs, or can it be neglected in new builds?

There is currently a parallel discussion about this. Yes, it does make a difference. But the less heating costs you have, the smaller the effect. I heat my 120sqm (about 1300 sq ft) for well under €400 per year (including hot water). In that case, the ventilation system is actually more expensive than simply airing through windows (electricity, filters, initial costs). However, I wouldn’t focus on the cost, because the gain in comfort is enormous. After all, you are building instead of renting, which is probably the more economical option in the long run.

Olypen01 schrieb:

Are there any hygiene issues with central systems after several years?

No.

Olypen01 schrieb:

Is it possible to install pollen filters or even activated carbon filters in decentralized systems?

Absolutely! I’m not sure about activated carbon filters and don’t see a particular reason to install them. My ventilation units have both a coarse filter and a fine filter that removes all pollen.

Olypen01 schrieb:

What do you think of Scanhaus Marlow only installing window frame vents as standard equipment?

That’s what makes Scanhaus Marlow “cheap.” It’s a sign of a low-cost provider. You can do that if your budget is so limited that you can’t afford a ventilation system—whether centralized or decentralized. For me, that would be a deal-breaker.

If you’re building new, go for a centralized system. If your budget doesn’t allow it or you’re renovating, choose decentralized. Window ventilation is only for fresh air purists who can’t live without open windows and need that “feeling.”

Olypen01 schrieb:

How is the noise level with the different systems? Especially with the decentralized system, I wonder how much you can hear the fans, which are installed in every wall. I imagine it could be quite unpleasant in the bedroom if there is a constant humming or buzzing sound.

We currently have a decentralized system in the bedroom of our rental apartment. You can definitely hear it. Personally, I don’t mind at all—I sleep like a log—but my husband is bothered by it.

For our new build, we are installing a central system and have previously done a "test listening" at friends’ homes. In normal operation, you can’t hear anything, only in "party mode" at most. One family even has the ventilation unit in the attic directly above the bedroom, and even there you only hear something in party mode, which is still quieter than our noisy decentralized unit.

Olypen01 schrieb:

Are there any hygiene concerns with central systems after a few years? You have relatively long ductwork throughout the house, which you can’t easily clean if something starts to spoil.

Friends built with a central ventilation system about 8 years ago and recently had a particle test (mold spores) done around the birth of their first child, due to exactly those concerns. The test showed no issues.

Olypen01 schrieb:

Hello everyone,
we are considering building a house and are currently having initial discussions with various providers. So far, we have spoken with three companies, and each offer includes a different ventilation concept:

Danwood: Central ventilation system with heat recovery

Heinz von Heiden: Central exhaust ventilation system with passive supply air and no heat recovery (air in the bathroom, kitchen, and utility room is actively expelled outdoors by fans; in the other rooms, air is passively drawn in through corresponding vents)

Scanhaus Marlow: Standard features only include window frame vents. For an extra cost, a decentralized ventilation system with heat recovery is available.

At the moment, we are quite unsure about the advantages and disadvantages of the different systems and don’t really know which direction to take. Therefore, we would appreciate expert feedback.

In particular, we have the following questions:

What is the noise level like with the different systems? Especially with the decentralized system, I wonder how noticeable the fans are, since they are installed in every wall. I imagine it could be quite disturbing if there is a constant humming or buzzing sound, especially in the bedroom.

How significant is the effect of heat recovery? Heinz von Heiden’s system does not include it at all. Does this have a noticeable impact on heating costs, or can it be neglected in a new build?

Are there potential hygiene issues with central systems after several years? There are relatively long ducts throughout the house that cannot be easily cleaned if something starts to stagnate or decay.

Do decentralized systems also allow for the installation of pollen filters or possibly even activated carbon filters? Or is this exclusively possible with central systems?

How would you assess the fact that Scanhaus Marlow only installs window frame vents as standard? According to the advisor, ventilating twice a day is sufficient to prevent mold problems. However, I am rather skeptical about this after reading up on the subject and tend to prefer building with a ventilation system.

Check out the discussion "Is a ventilation system worth it?" here in the forum. Much has already been said about the pros and cons.
Regarding mold issues, I can tell you that it actually works well without a ventilation system (and without window frame vents); we have lived like this for almost four years in our KfW55 house. We open windows early in the morning and in the evening, and during the day, doors are opened often enough through normal daily activities. Whenever possible, our windows and doors remain open.
Whether you see the system as a comfort upgrade and want to have one is ultimately your decision, but keep in mind that besides the cost, these systems also take up space.

Olypen01 schrieb:

We are planning to build and are currently having initial talks with relevant providers. So far, we have spoken with three companies and found a different ventilation concept in each offer:

Danhaus, Heinz von Heiden, and Scanhaus Marlow already represent quite a diverse mix, and the ventilation systems are roughly the seventh decimal place if you want to differentiate within this group. It’s very good that you’re open to considering Holzer and Steiner on equal terms. However, choosing between these candidates on the one hand, and by way of Excel spreadsheets on the other, shows your amateur status to an extent that requires professional advice and guidance. You should definitely do a lot more side research here. Danhaus is a quite recommendable wood-frame builder, who in my experience competes well with Steiner’s Viebrockhaus. Scanhaus Marlow, on the other hand, is a low-cost provider with a finish-your-own-home standard. And Gabrielle’s favorite Heinz, from my point of view, only has two really strong departments: marketing and legal. Anyone who then approaches it the way you do, in my opinion, is more likely to become a victim rather than a king client.

Which house design did you use to approach these companies in the first place, and which other companies were in the running before this semi-final stage?
Look up the keywords “dough rest / setting the course” here to understand how I provide advice to those making comparisons.

I wouldn’t compare Danhaus with Scanhaus Marlow; Hanse Haus would come to mind instead. For the Steiners, I would choose a locally owned company, which does not apply to Heinz von Heiden.

nordanney schrieb:

There is currently a parallel discussion going on.

That would be here: https://www.hausbau-forum.de/threads/rechnet-sich-eine-lueftungsanlage-spart-man-damit-geld.49160/

A mechanical ventilation system with heat recovery is not entirely standard yet, similar to how manual transmissions and crank windows still exist in cars today, while automatic transmissions or DSG and electric windows have long been on their way from niche to mainstream, at least in the front seats. If you want mechanical ventilation, a decentralized solution for new builds is generally only recommended in exceptional cases, since a central system with full coverage is more cost-effective (and heat recovery works better in a centralized pool than in isolated units). Window-frame ventilation I consider acceptable, but to mention it in the same breath as ventilation systems is a joke.

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motorradsilke schrieb:

The costs also involve space, not just money.

A small note: decentralized systems do not take up space at all (regarding costs and space). There are options, for example, designed for installation in window reveals, even with cross-flow heat exchangers (i.e., exactly like a central system), so the noise level is almost reduced to zero.