Decentralized residential ventilation, exhaust air heat pump - experiences?

Hello everyone,

My wife and I want to start building our single-family house near Bonn during this year. After numerous consultation talks (both in the area of prefabricated construction and solid construction), the company V***Haus is currently very popular with us as a builder. Unlike many other builders, however, V***Haus does not install a central, but a decentralized ventilation system. The fresh supply air is fed directly through soundproof valves in the walls and not, as with central systems, drawn in at one place, heated by the exhaust air in a heat exchanger, and then distributed through a pipe system; the heat stored in the exhaust air is still not wasted but is supplied to the underfloor heating in a so-called exhaust air heat pump by the company Nibe. From my point of view, such a system offers (like many things) some advantages and disadvantages:

Pros:
+ Air does not have to be fed through a maintenance-intensive pipe system
+ Air quality is therefore higher
+ Germ and mold formation in the pipe system is not a factor
+ Waste heat can be used more efficiently in the exhaust air heat pump than in the heat exchanger of a central ventilation system

Cons:
- The air that is led into the rooms has outside temperature (warm in summer, cold in winter)
- If the valves do not close properly, drafts can occur
- Possibly analogous to "tilt window ventilation"

Basically, I find the concept very good, and I also like the way the exhaust air heat pump works compared to a conventional air-water pump. However, my fear (or worry) is that at some point in the deep winter, I will be sitting there and (I am deliberately exaggerating now) -20° C cold outside air will flow in through the valves while the underfloor heating below me tries hard to keep the room at temperature at 50° C. It is generally agreed nowadays that permanent tilt ventilation is poison for the building fabric. What is the difference here? Is it in the air throughput, which is simply much lower (and above all controlled) with such a ventilation system???

My question is therefore: Does anyone have experience with this decentralized ventilation system? What do you think about it? Where do YOU see advantages and disadvantages??? I would appreciate a few of your thoughts on the subject.

Best regards,
Chris

+ Air does not have to be supplied through a maintenance-intensive duct system

One cannot really speak of maintenance-intensive. When the systems are operated with filters, hardly anything accumulates there.

+ Air quality is therefore higher

No, see the last point. Besides, the air is filtered in a central controlled residential ventilation system.

+ Germ and mold formation in the duct system is not a factor

This is actually not a factor even in a central controlled residential ventilation system. However, it is often used as an argument by sellers of decentralized systems.

+ Waste heat can be used more efficiently in the exhaust air heat pump than in the heat exchanger of a central residential ventilation system

That is a claim that first needs to be proven. If you research something on the internet, you will also find practical experiences with the specified exhaust air heat pump. Also regarding the "efficiency" of the system.

The air that is directed into the rooms has outside temperature (warm in summer, cold in winter)

This point would disqualify the system for me.

DerBjörn has already written quite a bit: I agree with that. How is something supposed to get into the pipes that would mold there? And no moisture should arise inside, otherwise that would indicate a construction defect.

We have a central system and would never want to do without it for any money. Currently, when it is around 0 degrees outside, the blown-in supply air is about 15-18 degrees, which already leads to a lowering of the room temperature here if the heating is turned off at night.

Well, if you already have the option to choose, I would only install a central system in a new building and nothing else...

As others have already written, the arguments are unfounded...

+ Air does not have to be supplied through a maintenance-intensive pipe system

As already mentioned...not more maintenance-intensive than a decentralized system.

+ Air quality therefore higher

I seriously doubt that!

+ Germ and mold formation in the pipe system is not a factor

Both variants have the same conditions with professional installation.

+ Waste heat can be used more efficiently in the exhaust air heat pump than in the heat exchanger of a central residential ventilation system

well, that is rather a statement from a glossy brochure without evidence...

- The air supplied to the rooms has outside temperature (warm in summer, cold in winter)

yup, that's true and you can clearly notice it.

- If the valves do not close properly, drafts can occur

yup.

- Possibly analogous to "tilt ventilation"

yes, also.

besides:

- More penetrations in the facade, thus greater potential for errors during installation, formation of thermal bridges, etc.
- Stronger soiling of the facade at the valves
- Higher filter costs, because "special" filters are needed which have special shapes etc. and a higher number of these are required than with a central controlled residential ventilation system
and so on

Hello Chris,

My question is therefore: Does anyone of you have experience with this system of decentralized residential ventilation? What do you think about it? Where do YOU see advantages and disadvantages??? I would appreciate a few of your thoughts on the subject.

As you can already see from the previous answers, the topic of decentralized or centralized ventilation is a Jehovah topic.

I can tell you for our construction project, where a decentralized system was installed, that our builders are very satisfied with this ventilation system and the "cons" you described do not occur. However, it depends on which provider is chosen and at which position in the room the fans are installed so that hardly any draft sensation occurs. The same satisfaction applies to our customers who have installed a centralized system. So it is not only about personal preference but also about the available budget. You have the agony of choice; only as a rule of thumb, in my opinion, it should always apply: better a decentralized than no ventilation system at all.

The red colleague certainly doesn’t build few houses – so why don’t you ask for reference addresses? Or even better – go to a development area in your vicinity and ask the existing customers of this provider about their experiences (can also be found on the internet). You should also be able to recognize their houses without signs. Furthermore, you can also inquire about the running costs of the installed exhaust air heat pump.

Rhenish regards

Hello,

...Basically, I think the concept is very good, and I also like the way the exhaust air heat pump works compared to a conventional air-water pump. However, my concern (or fear) is that at some point in the deep winter, I will be sitting there and (I am deliberately exaggerating now) -20°C cold outside air will flow in through the valves, while underneath me the underfloor heating is desperately trying to keep the room at temperature at 50°C...

An underfloor heating optimized for heat pumps has at best ~35°C flow temperature! By the way, your concerns are justified!

...My question is therefore: Does anyone of you have experience with this decentralized residential ventilation system? ...

With the overall construction, yes. First of all, it must be clarified that one/this exhaust air heat pump is sensible at all! Otherwise, besides this strange supply air, significantly excessive consumption costs.
I have already prepared expert reports on this! Talk to defrauded building owners! There is even a separate forum for dissatisfied customers!

Best regards

NB: Note regarding reference addresses. Many general contractors/pay well for corresponding information! So look for the address yourself, do not have it given by the provider!