ᐅ Mechanical ventilation with heat recovery: no – explanation provided in the text.
Created on: 15 Jul 2015 00:00
G
Grym
For a long time, I was very much in favor of controlled residential ventilation, but I have now revised my opinion. First, some basic considerations:
- Modern houses are built so tightly that additional mechanical ventilation is necessary; otherwise, windows must be opened several times a day, summer and winter, for airing out
- Whether this ventilation is manual or automatic is a matter of comfort
- Whether this ventilation includes heat recovery or not is a question of economic efficiency
When considering economic efficiency, cleaning costs must be included. A reputable provider who only sells controlled residential ventilation estimated these costs at 700 EUR, with a recommended cleaning interval of at least every 5 years. However, in the demonstration house, the first cleaning was done after only 2 years because a microbial test detected contamination in the supply air exceeding the limit values (I don’t know the exact limits, but if the seller says cleaning after 2 years was necessary, I take their word for it—the company does not sell a house without controlled residential ventilation).
Depending on whether you divide the 700 EUR over 5 years or 2 years, the annual maintenance costs come to between 140 and 350 EUR.
The unit itself consumes electrical energy, approximately 250–400 kWh_el per year, which costs between 63 and 100 EUR annually.
The controlled residential ventilation system is a technical device; assuming a service life of 15 years, removal and disposal of the old unit, a new unit, and commissioning are estimated at around 5,000 EUR. This results in an annual depreciation of 333 EUR. If the ventilation system is expected to last 20 years, with disposal, new unit, and commissioning costs totaling 4,000 EUR, then depreciation is 200 EUR per year.
For new filters, maintenance, and minor repairs, I estimate a flat rate of 100 EUR.
Total annual costs in the best case scenario: 140 + 63 + 200 + 100 = 503 EUR
Total annual costs in the worst case scenario: 350 + 100 + 333 + 100 = 883 EUR
The savings effect is roughly estimated at about 2,000 kWh_thermal up to over 3,000 kWh_thermal. 2,000 kWh_thermal equate to 2,000 kWh of gas at 5.5 cents or 400–500 kWh_el at 20 cents (heat pump tariff) or 25 cents (household electricity). This results in savings of about 110 EUR (gas), 125 EUR (air-source heat pump with household electricity), or 80 EUR (ground-source heat pump with heat pump electricity).
At 3,500 EUR savings, this corresponds to 193 EUR (gas), 219 EUR (worst-case heat pump), or 140 EUR (best-case heat pump).
If you compare the best-case controlled ventilation with the worst-case heat pump, you get 503 EUR - 219 EUR = 284 EUR. The other way around is 883 EUR - 140 EUR = 743 EUR.
No matter how you look at it, controlled ventilation with heat recovery cannot even save the running costs. Therefore, in my opinion, the best system—especially to avoid hygienic problems in the house—is exhaust air modules in wet rooms combined with window rebate ventilation or an external wall air inlet. Decentralized controlled ventilation systems with heat recovery do not have such high cleaning costs, but even they would never recoup the additional cost of heat recovery. Additionally, these devices must be placed in bedrooms and living areas, which creates noise. Pure exhaust air systems without heat recovery are suitable in rooms where quiet noises are less disturbing (kitchens, toilets, utility rooms, bathrooms) and can even be switched off for hours (bathroom). Modern window rebates work without drafts and reduce sound insulation by only 1 to 2 dB. Anyone living in a quiet residential area probably doesn’t mind.
I look forward to the discussion, but please keep it relevant to the topic. I am not questioning the necessity of non-user-dependent mechanical ventilation; my focus is only on central heat recovery. Central heat recovery requires the duct system, which incurs high cleaning costs, as well as a complex technical device with limited service life and high costs (unlike a standard exhaust air module without heat recovery). Controlled ventilation without heat recovery operates without the duct system.
- Modern houses are built so tightly that additional mechanical ventilation is necessary; otherwise, windows must be opened several times a day, summer and winter, for airing out
- Whether this ventilation is manual or automatic is a matter of comfort
- Whether this ventilation includes heat recovery or not is a question of economic efficiency
When considering economic efficiency, cleaning costs must be included. A reputable provider who only sells controlled residential ventilation estimated these costs at 700 EUR, with a recommended cleaning interval of at least every 5 years. However, in the demonstration house, the first cleaning was done after only 2 years because a microbial test detected contamination in the supply air exceeding the limit values (I don’t know the exact limits, but if the seller says cleaning after 2 years was necessary, I take their word for it—the company does not sell a house without controlled residential ventilation).
Depending on whether you divide the 700 EUR over 5 years or 2 years, the annual maintenance costs come to between 140 and 350 EUR.
The unit itself consumes electrical energy, approximately 250–400 kWh_el per year, which costs between 63 and 100 EUR annually.
The controlled residential ventilation system is a technical device; assuming a service life of 15 years, removal and disposal of the old unit, a new unit, and commissioning are estimated at around 5,000 EUR. This results in an annual depreciation of 333 EUR. If the ventilation system is expected to last 20 years, with disposal, new unit, and commissioning costs totaling 4,000 EUR, then depreciation is 200 EUR per year.
For new filters, maintenance, and minor repairs, I estimate a flat rate of 100 EUR.
Total annual costs in the best case scenario: 140 + 63 + 200 + 100 = 503 EUR
Total annual costs in the worst case scenario: 350 + 100 + 333 + 100 = 883 EUR
The savings effect is roughly estimated at about 2,000 kWh_thermal up to over 3,000 kWh_thermal. 2,000 kWh_thermal equate to 2,000 kWh of gas at 5.5 cents or 400–500 kWh_el at 20 cents (heat pump tariff) or 25 cents (household electricity). This results in savings of about 110 EUR (gas), 125 EUR (air-source heat pump with household electricity), or 80 EUR (ground-source heat pump with heat pump electricity).
At 3,500 EUR savings, this corresponds to 193 EUR (gas), 219 EUR (worst-case heat pump), or 140 EUR (best-case heat pump).
If you compare the best-case controlled ventilation with the worst-case heat pump, you get 503 EUR - 219 EUR = 284 EUR. The other way around is 883 EUR - 140 EUR = 743 EUR.
No matter how you look at it, controlled ventilation with heat recovery cannot even save the running costs. Therefore, in my opinion, the best system—especially to avoid hygienic problems in the house—is exhaust air modules in wet rooms combined with window rebate ventilation or an external wall air inlet. Decentralized controlled ventilation systems with heat recovery do not have such high cleaning costs, but even they would never recoup the additional cost of heat recovery. Additionally, these devices must be placed in bedrooms and living areas, which creates noise. Pure exhaust air systems without heat recovery are suitable in rooms where quiet noises are less disturbing (kitchens, toilets, utility rooms, bathrooms) and can even be switched off for hours (bathroom). Modern window rebates work without drafts and reduce sound insulation by only 1 to 2 dB. Anyone living in a quiet residential area probably doesn’t mind.
I look forward to the discussion, but please keep it relevant to the topic. I am not questioning the necessity of non-user-dependent mechanical ventilation; my focus is only on central heat recovery. Central heat recovery requires the duct system, which incurs high cleaning costs, as well as a complex technical device with limited service life and high costs (unlike a standard exhaust air module without heat recovery). Controlled ventilation without heat recovery operates without the duct system.
N
nordanney15 Jul 2015 12:10Ozone cleaning sounds quite advanced... However, if there are damp areas in the piping system, the pathogens are likely to return after a few days.
N
nordanney15 Jul 2015 12:15You
Apparently, you’ll believe anything you’re told...
Try doing an ozone cleaning in your toilet or your wife’s handbag (those can sometimes be even nastier inside than toilets). Then also under all cabinets, behind the kitchen units, etc.
Your salesperson can probably recommend a good provider (who will then be happy every year to find another fool with germophobia).
I’m out of this discussion; it’s getting too childish for me since Grym is too resistant—only open to salespeople. I would have liked to have you as a customer.
Grym schrieb:
I mentioned this brush cleaning method to the architect as well. At first, he just gave a tired smile and told me that this is no longer how it’s done nowadays. That used to be a cleaning system in the past. It doesn’t actually kill germs either. Nowadays, high-dose ozone cleaning is used, and during that time, a few hours, you obviously shouldn’t be inside the house.
So your strange online shop told you never to clean and if so, only with such a brush? Are you sure you were properly advised and not just taken for a ride? My salesperson and the architect present at the time at least honestly told me about maintenance intervals and explained that my conventional, old methods wouldn’t work. You just have to realistically factor in those costs of 700 euros every 5 years.
Apparently, you’ll believe anything you’re told...
Try doing an ozone cleaning in your toilet or your wife’s handbag (those can sometimes be even nastier inside than toilets). Then also under all cabinets, behind the kitchen units, etc.
Your salesperson can probably recommend a good provider (who will then be happy every year to find another fool with germophobia).
I’m out of this discussion; it’s getting too childish for me since Grym is too resistant—only open to salespeople. I would have liked to have you as a customer.
S
Sebastian7915 Jul 2015 12:16No, my "strange online shop" never told me to "never clean"—that was never even an issue, and I don’t see that anywhere from them either. I came with specific requirements, which were met. So there’s no need to throw around clichés like “being ripped off”...
And as I said, your architect from that model park (I could just laugh) is supposedly an expert in ventilation systems? That’s usually not their field... but I guess you’re dealing with an all-round professional there.
As I said, your 700 euros are already ridiculous if it’s just about the ozone cleaning. I do that completely for free at my place—if you hire that out externally, it might cost about 100 euros.
Besides that: So you’re supposed to do this every 5 years? You still haven’t been able to explain why that would be a breeding ground for germs. And why only after 5 years? Why not every few weeks or months? Germs multiply exponentially... but what am I telling you about numbers?
By the way, the “old brush method” might actually clean the breeding grounds of germs—if you were open-minded, you would have included that in your reasoning. But ozone cleaning only makes sense if you eliminate the root cause of the “contamination”…
And as I said, your architect from that model park (I could just laugh) is supposedly an expert in ventilation systems? That’s usually not their field... but I guess you’re dealing with an all-round professional there.
As I said, your 700 euros are already ridiculous if it’s just about the ozone cleaning. I do that completely for free at my place—if you hire that out externally, it might cost about 100 euros.
Besides that: So you’re supposed to do this every 5 years? You still haven’t been able to explain why that would be a breeding ground for germs. And why only after 5 years? Why not every few weeks or months? Germs multiply exponentially... but what am I telling you about numbers?
By the way, the “old brush method” might actually clean the breeding grounds of germs—if you were open-minded, you would have included that in your reasoning. But ozone cleaning only makes sense if you eliminate the root cause of the “contamination”…
If the mentioned company installs controlled ventilation systems in every house, then the architect should have some knowledge of the subject. No, he did not name a specific company. He also knew that we come from another city and therefore understood that we would not choose his local cleaning company because we plan to live and build elsewhere. Both he and the salesperson honestly informed me that a controlled ventilation system is not a maintenance-free technical installation and that, similar to a gas boiler, it requires regular inspections. Like industrial air conditioning systems, it also needs regular cleaning and disinfection.
There is considerably less air exchange behind my furniture than in ventilation ducts, so there is less germ entry. Don’t worry, the furniture is naturally placed 10cm (5 inches) away from the wall. Still, far fewer germs enter there compared to ventilation ducts, which circulate the entire air volume multiple times and are therefore exposed to many more germs per unit of time.
There is considerably less air exchange behind my furniture than in ventilation ducts, so there is less germ entry. Don’t worry, the furniture is naturally placed 10cm (5 inches) away from the wall. Still, far fewer germs enter there compared to ventilation ducts, which circulate the entire air volume multiple times and are therefore exposed to many more germs per unit of time.
S
Sebastian7915 Jul 2015 12:28Now an air conditioning system is being equated with a controlled residential ventilation system – as I said, truly professional statements. And I don’t understand why an architect at a model home park should still have expertise in controlled residential ventilation systems – what is their role there? Why do they continue to oversee the houses years after the occupants have moved in?
turhanet schrieb:
I think it’s great, Grym, that you are engaging with the topic and bravely sharing your perspective here—that’s what makes a forum lively. Unfortunately, I find the responses today somewhat unsatisfactory and subjective. I am also more in favor of a mechanical ventilation system with heat recovery. Nevertheless, it’s always good to look beyond the usual scope. What arguments would not fit regarding Grym’s proposed solution?@turhanet is right.
I also know @Grym from other forum posts and am aware that he can sometimes be a bit difficult (not to say stubborn or resistant to learning).
However, he has posed a valid question here, based on statements made by both a seller and an architect. Both would probably prefer to sell something and usually try to address potential counterarguments. In this case, though, that isn’t happening — so a follow-up question is justified.
Right from the start, @Grym’s question was met with a negative attitude (likely influenced by previous threads), which I do not find appropriate in this case.
Since I don’t have a mechanical ventilation system (but a decentralized one), I can only respond in general terms.
A ventilation system with heat recovery will never pay for itself financially. That is simply the reality. Anyone who purchases such a system is usually focused more on comfort (and the necessary ventilation).
It was mentioned earlier in this thread that a lot of moisture accumulates especially in the bedroom. We noticed this when we had to clean our filters in February. A significant amount of moisture passes through.
Our general contractor also proposed exhaust fans integrated in the window rebate—argument being: Nothing else makes economic sense. Due to the negative pressure created by these exhaust fans in moist rooms, used air is drawn out from other rooms and vented outside. However, these exhaust fans would need to run continuously to ensure proper air exchange. That means, for example, you would constantly draw in cold air during the winter, which then has to be reheated.
Regarding the comments about cleaning and microbial growth, I can’t say much. However, since the reasoning “moisture leads to microbial growth – where would moisture come from inside the intake ducts?” makes sense, I suspect there may be other construction defects. Or perhaps the microbial growth occurred in the exhaust ducts (where moist air passes through)? Would that be possible? And to what extent could such microbes enter your home, given the airflow would normally carry them outside?
Similar topics