Hello everyone, the title already describes the problem. Approximately 20% humidity in all living and sleeping rooms. We moved in about two weeks ago. That can’t be normal, right? I expected such low humidity only after 2-3 years, but not right from the start...
The first night in the house was really horrible. On top of that, we have been dealing with colds and coughing the whole time. We now have a humidifier running all night in the bedroom (starting in the evening, about 12 hours total) and wake up with around 35-40% humidity.
Could something be set incorrectly in the mechanical ventilation system with heat recovery, or is this low humidity normal in a new house?
What can we do? Apart from the bedroom, we don’t notice it being a problem in any other room. Enthalpy exchangers are supposed to increase humidity by a maximum of 5%, right?!
Thanks for your feedback and best regards
The first night in the house was really horrible. On top of that, we have been dealing with colds and coughing the whole time. We now have a humidifier running all night in the bedroom (starting in the evening, about 12 hours total) and wake up with around 35-40% humidity.
Could something be set incorrectly in the mechanical ventilation system with heat recovery, or is this low humidity normal in a new house?
What can we do? Apart from the bedroom, we don’t notice it being a problem in any other room. Enthalpy exchangers are supposed to increase humidity by a maximum of 5%, right?!
Thanks for your feedback and best regards
But hey, mechanical ventilation with heat recovery is an absolute must; anyone building today without it is essentially building an old-style house! How often do you hear that here every day? You build an airtight building and need mechanical ventilation to remove moisture to prevent mold. Then you put humidifiers in every corner to add moisture so that living in the airtight building is even possible. I sometimes find our architect a bit old-fashioned regarding the latest building technologies, but his saying, "why fix something technically if you can get it right from a building physics perspective in the first place," is growing on me.
Just saying.
Just saying.
R
RotorMotor5 Mar 2023 11:08[QUOTE="Araknis, post: 621425, member: 57358"]
But hey, mechanical ventilation with heat recovery is an absolute must. Anyone building today without it is basically constructing an old building! How often do you read this here every day? You build a tight house and need mechanical ventilation with heat recovery to remove moisture so that the tight building doesn’t get moldy. Then people put humidifiers in every corner to add moisture so that living in the tight house is even possible. I sometimes find our architect a bit old-fashioned regarding the latest building technologies, but I increasingly like his saying: “Why fix something technically if you can get it right from a building physics perspective in the first place.”
And how do you remove the moisture "correctly from a building physics perspective" right away?
And how is it with CO2?
And yes, mechanical ventilation with heat recovery only with an enthalpy exchanger.
But hey, mechanical ventilation with heat recovery is an absolute must. Anyone building today without it is basically constructing an old building! How often do you read this here every day? You build a tight house and need mechanical ventilation with heat recovery to remove moisture so that the tight building doesn’t get moldy. Then people put humidifiers in every corner to add moisture so that living in the tight house is even possible. I sometimes find our architect a bit old-fashioned regarding the latest building technologies, but I increasingly like his saying: “Why fix something technically if you can get it right from a building physics perspective in the first place.”
And how do you remove the moisture "correctly from a building physics perspective" right away?
And how is it with CO2?
And yes, mechanical ventilation with heat recovery only with an enthalpy exchanger.
Masonry house with good plaster and ventilation, classic as usual. For the price of a controlled residential ventilation system including the additional measures you have to take afterwards (plants everywhere—which wouldn’t be an option for us, humidifiers), I can ventilate warm air out for a very long time.
Of course, a controlled residential ventilation system is convenient for air quality (not for comfort!), but it is not a cure-all and certainly not without issues.
Of course, a controlled residential ventilation system is convenient for air quality (not for comfort!), but it is not a cure-all and certainly not without issues.
Hmm, there seems to be a misunderstanding here.
If you ventilate manually properly, you have the same dry air problem as with a mechanical ventilation system without an enthalpy heat exchanger, but with additional effort and more heat loss.
The dry air does not result from any technical conversion in the mechanical ventilation system; it happens because moist indoor air is exchanged with dry (because cold) outdoor air. In a mechanical ventilation system, at least 80-90% of the heat is retained.
If you want to achieve the same air exchange manually, you also have the heat loss and need to run through the entire house at least three times two times (open and close) per day.
Most people don’t do that and therefore have better indoor humidity. However, there is still some risk of mold in case of doubt.
If you ventilate manually properly, you have the same dry air problem as with a mechanical ventilation system without an enthalpy heat exchanger, but with additional effort and more heat loss.
The dry air does not result from any technical conversion in the mechanical ventilation system; it happens because moist indoor air is exchanged with dry (because cold) outdoor air. In a mechanical ventilation system, at least 80-90% of the heat is retained.
If you want to achieve the same air exchange manually, you also have the heat loss and need to run through the entire house at least three times two times (open and close) per day.
Most people don’t do that and therefore have better indoor humidity. However, there is still some risk of mold in case of doubt.
W
WilderSueden5 Mar 2023 11:37We have discussed this topic many times before, so I did the calculations. To heat 1 cubic meter of air by 1 degree requires 0.33 Wh. Now you just need to factor in how often you ventilate and the temperature difference. Depending on the numbers, with 3 air changes (= ventilating 3 times), you end up with 6–10 kWh per square meter per winter. Considering a calculated heating demand of 35 kWh for an EH55 standard house, this is a significant amount.
Any type of ventilation dries out the air, whether through mechanical ventilation with heat recovery or manually. The difference is that most people are ventilating properly for the first time when using mechanical ventilation with heat recovery. Additionally, there are challenges with ventilation itself. In still air conditions, you have poor air exchange. When it is windy, windows and doors may slam shut and papers can blow around. Interior hallways or rooms with small windows often have poor air exchange.
Any type of ventilation dries out the air, whether through mechanical ventilation with heat recovery or manually. The difference is that most people are ventilating properly for the first time when using mechanical ventilation with heat recovery. Additionally, there are challenges with ventilation itself. In still air conditions, you have poor air exchange. When it is windy, windows and doors may slam shut and papers can blow around. Interior hallways or rooms with small windows often have poor air exchange.
R
RotorMotor5 Mar 2023 11:49WilderSueden schrieb:
We have discussed this many times before, so I did some calculations. To heat 1 cubic meter of air by 1 degree, you need 0.33 Wh. Now you just have to factor in how often you ventilate and the temperature difference. Depending on the numbers, with 3 air changes (= ventilating 3 times), you end up with 6-10 kWh per square meter per winter. With a calculated heating demand of 35 kWh for an EH55 standard home, that is certainly a relevant magnitude. I am always a fan of calculations, but those without concrete numbers make little sense.
The first result from a search gives 70 kWh/m²/a, which is 7 to 10 times higher than your value.
One main problem seems to be that you are calculating based on exchanging only the air. While that may be true for a mechanical ventilation system with heat recovery, when windows are opened, floors, furniture, walls, etc., also cool down and need to be reheated.
In addition, ventilating only three times in a modern house is far from sufficient to maintain hygienic air quality.
WilderSueden schrieb:
All types of ventilation dry out the air, whether through mechanical ventilation or manual airing. The difference is that most people, when using mechanical ventilation for the first time, are actually ventilating properly for the first time in their lives. Then there is the issue with the ventilation itself. On calm days you get poor air exchange. When it is windy, windows and doors slam, papers blow around. Interior corridors or rooms with small window openings often have poor air exchange. I fully agree with this.
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