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.
B
Bieber08155 Jan 2016 10:12That’s quite an achievement: writing an article about ventilation and indoor air quality without once mentioning the CO2 concentration in indoor air!
We currently rely on ventilation through drafty windows in our old building (despite expensive additional seals from tesa). With a normal indoor temperature, the window reveal temperature recently dropped below 15°C (59°F). The cold draft is also uncomfortable.
Radiant heating systems might be interesting, why not. Still, I wouldn’t want to do without a mechanical ventilation system with heat recovery. And I would argue that no matter how sophisticated a (radiant) heating system is, it won’t prevent cold window reveals if you constantly ventilate through tilted or leaky windows.
We currently rely on ventilation through drafty windows in our old building (despite expensive additional seals from tesa). With a normal indoor temperature, the window reveal temperature recently dropped below 15°C (59°F). The cold draft is also uncomfortable.
Radiant heating systems might be interesting, why not. Still, I wouldn’t want to do without a mechanical ventilation system with heat recovery. And I would argue that no matter how sophisticated a (radiant) heating system is, it won’t prevent cold window reveals if you constantly ventilate through tilted or leaky windows.
That is absolutely clear. As mentioned before, the article is somewhat sensationalized, so it shouldn’t be taken at face value. However, it does point out some of the partly absurd regulations and presents a few interesting ideas. That is all I wanted to say, no more and no less.
There are many controversial topics in construction, including mechanical ventilation with heat recovery. I just wanted to offer another perspective, because as a newcomer to this thread, one might almost think that mechanical ventilation with heat recovery is the only right solution. It has never hurt to question things critically.
There are many controversial topics in construction, including mechanical ventilation with heat recovery. I just wanted to offer another perspective, because as a newcomer to this thread, one might almost think that mechanical ventilation with heat recovery is the only right solution. It has never hurt to question things critically.
The article is quite one-sided and makes many claims without providing evidence.
Since airtight construction is mandatory in Germany, and underfloor heating (a combination of convection and radiant heating) is commonly used, controlled mechanical ventilation or frequent airing is necessary. Furthermore, even with radiant heating, fresh air is required for the occupants (as gym explained well), and humidity needs to be removed.
Since airtight construction is mandatory in Germany, and underfloor heating (a combination of convection and radiant heating) is commonly used, controlled mechanical ventilation or frequent airing is necessary. Furthermore, even with radiant heating, fresh air is required for the occupants (as gym explained well), and humidity needs to be removed.
The article is partly correct but does not provide any arguments against a ventilation system.
Main reasons in favor of controlled ventilation:
- The human need for fresh air
- Reducing CO2 concentration to a natural level
- Removing volatile organic compounds, which are always present everywhere (from carpets, furniture, plastics, building materials, etc.)
- Removing numerous other pollutants that inevitably occur, see here:
Link removed by moderation
Where does the article address even one of these issues? How are bricks and lime plaster supposed to help with any of these topics?
Briefly on the article’s section "too high air exchange rates" – who exchanges the entire indoor air 14 to 19 times? Answer: this happens in practically every older building. The regulations are only intended to ensure that newer, tighter buildings at least reach this level of air exchange.
Other remarkable works by the same author:
"The Myth of the Climate Catastrophe"
"DIN Standards – a Tool of Deception"
"The Impact of the Green-Aligned Alternative Understanding of Science on Research"
With this outstanding knowledge, he has rightfully earned his place on Konrad Fischer’s website.
Main reasons in favor of controlled ventilation:
- The human need for fresh air
- Reducing CO2 concentration to a natural level
- Removing volatile organic compounds, which are always present everywhere (from carpets, furniture, plastics, building materials, etc.)
- Removing numerous other pollutants that inevitably occur, see here:
Link removed by moderation
Where does the article address even one of these issues? How are bricks and lime plaster supposed to help with any of these topics?
Briefly on the article’s section "too high air exchange rates" – who exchanges the entire indoor air 14 to 19 times? Answer: this happens in practically every older building. The regulations are only intended to ensure that newer, tighter buildings at least reach this level of air exchange.
Other remarkable works by the same author:
"The Myth of the Climate Catastrophe"
"DIN Standards – a Tool of Deception"
"The Impact of the Green-Aligned Alternative Understanding of Science on Research"
With this outstanding knowledge, he has rightfully earned his place on Konrad Fischer’s website.
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