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.
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Sebastian7915 Jul 2015 10:58Exactly – but it’s not rocket science either.
I don’t have a ground heat exchanger – for me, it’s more of a breeding ground for germs, it’s expensive (just the intake towers), and the benefit is too low.
Air intake is on the north gable, air exhaust on the south gable – cooling is done by air conditioning.
I don’t have a ground heat exchanger – for me, it’s more of a breeding ground for germs, it’s expensive (just the intake towers), and the benefit is too low.
Air intake is on the north gable, air exhaust on the south gable – cooling is done by air conditioning.
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nordanney15 Jul 2015 10:59Grym schrieb:
and why was the show house still contaminated? Not visible, but measurable. We cannot answer that for you. Maybe there was sloppy workmanship during construction—it can even happen with a show house.
If you are really that worried, just go with conventional or decentralized ventilation.
I find window frame ventilation or something similar to be terrible; first build airtight, then use windows for cross-ventilation.
What types of microbes and in what concentrations were found in the show house? Why only in the supply air? Is there a system with humidification (humidity = potential breeding ground for germs)? Where is the house located that such harmful microbes could even enter from outside?
You should confront your "facts" from the seller with these questions.
P.S. If the seller assures you that heating the house with lignite coal is the best option, would that also be a "fact" for you?
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Sebastian7915 Jul 2015 11:05The entire thread is based on a statement that has been set in stone and is not meant to be debated—just like the costs. These are assumed, continuously factored in somewhere, and then considered fixed. As with every thread by Grym...
This is the fundamental problem and what makes the original poster’s discussion itself unobjective.
What is wrong with Grym’s “solution” from an argumentative perspective?
This is the fundamental problem and what makes the original poster’s discussion itself unobjective.
What is wrong with Grym’s “solution” from an argumentative perspective?
- Single-family houses don’t have wet rooms
- He plans to use exhaust ventilation for bathrooms/kitchens—but a bedroom generates moisture for hours because of the occupants. The other living spaces are simply ignored.
- Uncontrolled penetrations through the exterior wall are casually mentioned—the fact that this undermines the airtight building envelope is treated as irrelevant...
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Sebastian7915 Jul 2015 11:42Oh, I just noticed that our Grymi started the exact same thread again in the green forum – unfortunately with the same results. Pretty trollish behavior...
But you wrote something interesting there: The mechanical ventilation system in the model house was cleaned using ozone? That’s supposed to be complicated and cost 700 Euros? That’s when you realize how much they’ve been ripping you off.
The cleaning is actually done with a special brush system, which you can borrow and do yourself, by the way.
And if that’s not enough for you: I can also “clean” it with ozone – no problem. It doesn’t even cost me anything.
But you wrote something interesting there: The mechanical ventilation system in the model house was cleaned using ozone? That’s supposed to be complicated and cost 700 Euros? That’s when you realize how much they’ve been ripping you off.
The cleaning is actually done with a special brush system, which you can borrow and do yourself, by the way.
And if that’s not enough for you: I can also “clean” it with ozone – no problem. It doesn’t even cost me anything.
I also mentioned this brush cleaning method to the architect. He just gave a tired smile and told me that this is no longer how it’s done today. It used to be a cleaning system, but it doesn’t actually kill germs. Nowadays, high-dose ozone cleaning is used, and during that time—several hours—of course, you shouldn’t stay inside the house.
So your strange online store told you never to clean at all, or if you do, only with a brush like that? Are you sure you were properly advised and not just taken advantage of? At least my seller and the architect present gave me honest maintenance intervals and also explained that my conventional, old methods won’t work. You just have to realistically factor in those costs of 700 euros every 5 years.
So your strange online store told you never to clean at all, or if you do, only with a brush like that? Are you sure you were properly advised and not just taken advantage of? At least my seller and the architect present gave me honest maintenance intervals and also explained that my conventional, old methods won’t work. You just have to realistically factor in those costs of 700 euros every 5 years.
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