ᐅ Mechanical ventilation with heat recovery: no – explanation provided in the text.
Created on: 15 Jul 2015 00:00
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GrymFor 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.
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Sebastian7915 Jul 2015 07:57A properly installed system equipped with filters does not require cleaning – it seems you’ve been fed a lot of nonsense by a salesperson (!) and are now writing another long post with invoices that have no real basis and rely solely on your assumptions.
Where would the germs come from? From the outside air? In that case, better bury yourself quickly .
A mechanical ventilation system with heat recovery is not energy-efficient either – it’s purely for comfort. So for a controller like you, it’s definitely not suitable.
By the way, a mechanical ventilation system with heat recovery is not complex – it is actually quite simple in design, and the parts are easy to replace.
Where would the germs come from? From the outside air? In that case, better bury yourself quickly .
A mechanical ventilation system with heat recovery is not energy-efficient either – it’s purely for comfort. So for a controller like you, it’s definitely not suitable.
By the way, a mechanical ventilation system with heat recovery is not complex – it is actually quite simple in design, and the parts are easy to replace.
The seller and the architect were present. Germs are always and everywhere in the air, but they can multiply in such ducts. I doubt that a coarse filter can stop them. The same goes for fine dust, which easily passes through mechanical ventilation with heat recovery.
I don’t believe those two told me nonsense. They were straightforward. They just weren’t one of those notorious low-cost providers who try to sell at any cost. It’s completely clear to me that many other providers portray mechanical ventilation with heat recovery in a positive light. But even the well-known budget provider recommended cleaning every 10 years. Still, I trust the quality provider more—why would they give me arguments against mechanical ventilation with heat recovery? They don’t offer a house without it.
I do not dispute that user-independent forced ventilation is comfortable. But there are other solutions, as mentioned.
I don’t believe those two told me nonsense. They were straightforward. They just weren’t one of those notorious low-cost providers who try to sell at any cost. It’s completely clear to me that many other providers portray mechanical ventilation with heat recovery in a positive light. But even the well-known budget provider recommended cleaning every 10 years. Still, I trust the quality provider more—why would they give me arguments against mechanical ventilation with heat recovery? They don’t offer a house without it.
I do not dispute that user-independent forced ventilation is comfortable. But there are other solutions, as mentioned.
I don’t think this discussion about comfort and germs needs to be repeated every week, at least not in general. User- and situation-specific circumstances are not mentioned by you.
Besides, I don’t believe anyone has ever claimed that heat recovery or even a controlled residential ventilation system “pays off” financially...
Besides, I don’t believe anyone has ever claimed that heat recovery or even a controlled residential ventilation system “pays off” financially...
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Sebastian7915 Jul 2015 08:29Your solutions are neither comfortable nor efficient – I would never have something like that in my house. It’s not the 1970s anymore...
Sure, cleaning can be recommended – but why? Because filtered outside air is constantly (!) being drawn into the house? What exactly would be unusually contaminated? You could pour a jar of pure alcohol in there every year and it would definitely kill everything.
I know systems that have been running for 10 years and were cleaned – but nothing came out. There simply were no deposits – after all, these units are designed with as smooth a surface as possible.
However, I doubt you can have this kind of discussion with someone like you, since you have firmly fixed your assumptions and what you have heard, and in the end you only pay attention to the numbers, while, as so often, ignoring the human factor.
Sure, cleaning can be recommended – but why? Because filtered outside air is constantly (!) being drawn into the house? What exactly would be unusually contaminated? You could pour a jar of pure alcohol in there every year and it would definitely kill everything.
I know systems that have been running for 10 years and were cleaned – but nothing came out. There simply were no deposits – after all, these units are designed with as smooth a surface as possible.
However, I doubt you can have this kind of discussion with someone like you, since you have firmly fixed your assumptions and what you have heard, and in the end you only pay attention to the numbers, while, as so often, ignoring the human factor.
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