Ventilation system with heat recovery - sense or nonsense?

  • Erstellt am 2013-07-22 00:48:10

Bauexperte

2013-07-29 14:23:40
  • #1
Hello,


Is your planning engineer from your supplier’s company or externally consulted?

**Central exhaust air systems with decentralized outdoor air supply are technically simpler because they only require one exhaust air duct network but no supply air duct network. The outdoor air flows in through several wall outlets. However, these systems have a decisive disadvantage: In winter, the outdoor air enters the room cold and unheated, and its room-by-room dosing strongly depends on wind pressure.

Decentralized or central exhaust air systems blow the used air along with its heat out of the house. The heating system must warm up the cold outdoor air drawn into each room from outside temperature to room temperature. This costs energy. Compared to window ventilation, a pure exhaust air system therefore does not save energy, but only provides the comfort of automatic moisture removal, fresh air supply, and better controllability. In contrast, if you build a central supply and exhaust air system with ducts for both supply and exhaust air, these ducts can be combined and the cold fresh air can be preheated with the heat from the exhaust air in a supply-exhaust air heat exchanger – this also works with decentralized ventilation systems.

Modern supply and exhaust air systems with heat recovery (HR) recover up to 94 percent of the heat from the exhaust air. With them, the cold outdoor air can already be preheated in winter without additional heating energy, for example, to 17 degrees Celsius.

*** For health and economic reasons, controlled ventilation cannot be dispensed with in new buildings.

This consists of combining cost-effective thermal insulation measures with heat recovery from residential ventilation. On the market for residential ventilation devices, there is a wide variety of units that differ in their design and performance data. Interested buyers and planners depend on receiving manufacturer-neutral technical information on comparable individual units. This can become quite tedious. They have to compile this information laboriously. Moreover, a pure description of a device cannot always be satisfactory. A neutral test report that allows a direct comparison with other devices is helpful for selecting a suitable device.

A prerequisite for selecting the appropriate device is the creation of a meaningful ventilation concept.


In the 21st century, we can only really protect ourselves from cold, but not sensibly from heat. You can only approximate solving this problem by installing thicker masonry, consistently avoiding windows on the south side, or at least continuously shading them during the sun-rich season. Everything else is wishful thinking or requires the use of air conditioning units; by the way, you can forget a system that also designs underfloor heating to “cool” because you will hardly notice the 2° difference ... except in construction costs.


See above.

Moreover – from my humble point of view, there are only two options when choosing a ventilation system, which certainly should not be considered from the point of view of payback, because they do not and in my opinion must not. Mold in new buildings is something that cannot be combated with conventional window ventilation – especially not with window frame ventilation. The current – and certainly the future energy saving regulations – prescribe increasingly airtight houses; the sense and purpose can be debated, but it is futile, as this trend can no longer be reversed. Builders are forced to build increasingly airtight if they want to take advantage of KfW loans. With this airtightness of the building envelope, they buy into negative side effects, which in turn must be fought with even more technology. There are decentralized and centralized ventilation systems for this; every smart builder should resort to one of the two options – always with heat recovery – depending on budget.

From my experience; nowadays both partners in a building community (whether married couple or living community) work and are not in a position to ensure the ventilation requirements of the house within the first two years. Although the bricks are mostly glued today, the screed still brings a lot of water into the house, which also has to go out => and the inclined and "internet-educated" builder would also like to move into the house immediately after signing. The later residents also produce 4 liters of water per person per day, which is released into the single-family house atmosphere. This is even more true for terraced houses, since the – disrespectfully called – plastic foil prevents the removal of water.

A decentralized ventilation system with heat recovery costs around 5,000 euros for an average single-family house including ventilation concept. This usefully invested money saves the trouble with mold and also ensures that there is no musty smell in the house. The same applies to central systems, but the costs are around 13,000–15,000 euros and not all builders can afford that.

Sources:** Federation of Energy Consumers
*** TZWL e.V. – European Test Center for Residential Ventilation Devices e.V.


Rhenish regards
 

perlenmann

2013-07-29 16:47:55
  • #2
@Building expert and admin: Something is definitely wrong here. I can navigate normally here in the forum with Firefox, but my entry was also deleted. That's annoying. I don't have problems like this in any other forum.

So back to the topic:

Pro: Soundproofing (How should that be done in a decentralized way?)
You have already recognized the pollen filter yourself.
Ever opened the bathroom window slightly in winter, just a little draft with -10 degrees cold air?! Then you know what it means when the supply air is heated.
In terms of cost, the additional expenses probably will never pay off, but it is a gain in comfort.
Besides, a heat exchanger can also cool the warm air from outside if it is cooler inside the house. Still, usually the ventilation is set to minimum during heat and ventilated more strongly at night.
 

€uro

2013-07-30 07:29:46
  • #3
Hello construction expert,
Formulated so generally, this is incorrect. I have accompanied enough construction projects under the conditions of the Energy Saving Ordinance 2009 without a ventilation system. To this day, no trace of mold!
Correct, unfortunately the problem often lies already with these basics.
I see that differently. With sensible building construction (passive summer heat protection), a summer heat period can also be well endured without the use of technical cooling.
Only a knave would suspect evil here
To remove the temporary construction moisture, no ventilation system is needed permanently.
According to DIN 1946-6, window ventilation is also a recognized LtM (ventilation technical measure).
The business with the fear of mold, however, generates good sales. Especially general contractors/subcontractors make frequent use of this.
Best regards
 

Bauexperte

2013-07-30 13:03:41
  • #4
Hello €uro,


There have been exceptions and there always will be. I’m not writing this because I’m pulling it out of thin air; it corresponds to my experience over the past years. Of course, it’s also possible without ventilation, but then additional costs arise as you know.


I did not deny that and already indicated how it can work


I haven’t suspected that for a long time...


I know, but that doesn’t make it any better.


You can spread fear far better than I can

Rhenish greetings
 

Bauexperte

2013-07-30 13:05:45
  • #5
Hello Perlenmann,


The current Firefox is a problem, unfortunately there’s nothing that can be done about it. Your post was in any case deleted neither by the admin nor by me.

Rhenish regards
 

Shism

2013-07-30 17:26:37
  • #6


I somewhat heretically wonder if your experiences possibly come from the fact that you predominantly build with aerated concrete? I have often heard that aerated concrete stores more moisture during the construction phase and does not dry as quickly. The requirements for the ventilation behavior of the occupants are therefore particularly strict in the first 1-2 years...

On the topic of warmed supply air: even with window rebate ventilators, a certain amount of warming occurs... in measurements at -5° outside temperature, the supply air was already warmed to 8° upon entering the room... not at the level of a controlled residential ventilation system with heat recovery but significantly more than most would probably have estimated.
 

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