ᐅ Low Indoor Humidity Level (25%)

Mycraft schrieb:

Since everyone has their own preferences here, it’s not necessarily always the case. But globally, yes, above a certain outdoor temperature, the indoor air becomes very dry.

Unfortunately, yes. And my condolences for dealing with this uncomfortable heating system.
There are two reasons for the dry air with this type of heating:

1. The installed cross-flow heat exchanger only recovers the heat from the exhaust air. The humidity in the exhaust air is fully vented outside. Since the absolute moisture content of the supply air is much lower when it is cold outside, the relative humidity indoors drops to very uncomfortable levels. A solution is to replace the cross-flow exchanger with an enthalpy or rotary heat exchanger. These recover both heat and moisture from the exhaust air, which leads to higher indoor humidity. Unfortunately, the system manufacturer must offer such a heat exchanger option.

2. The second cause is the high required airflow volume to meet the heating demand, because air has a low heat capacity. This means that the colder it is outside, the lower the moisture content of the supply air, which is further worsened by the even higher airflow rates needed at low temperatures. To reduce this problem, the required airflow must be lowered. This can be done by:
- reducing the heating load by improving the building’s insulation (for example, the top floor ceiling) or lowering the indoor temperatures
- covering part of the heating load with an additional heater, such as a split air conditioner, which retains moisture inside, so the primary heating system brings in less outdoor air
- increasing the supply air temperature. This reduces the required supply air volume to meet the heating load, thus drying the house less. Unfortunately, this further reduces the already poor efficiency of the heating system.

Addressing the above causes will reduce the problem but not completely solve it. In my opinion, the ultimate solution is to install a humidification unit in the supply air of the heating system. This does cost some money, but it should eliminate the dry air issue. Try searching for something like Hygrobox Helios or simply air humidifiers for ventilation systems. A comfortable indoor climate is definitely worth around 5,000€ (approximately 5,400 USD). Maybe the builder will offer some goodwill compensation to fix the problem, since they installed this uncomfortable heating system without properly informing you about it.

Best regards, Nika

Comfort climate heating.
Such a system should be shown to a lawyer to determine whether there is a material defect. At 25% relative humidity, comfort is certainly not achievable.
Personally, I would find it quite amusing if there were any real consequences for this marketing nonsense. All this talk about climate walls and the like has become almost unbearable.

gnika77 schrieb:

IMHO, the ultimate solution is a humidification coil in the heating supply air

Something like that works great but has a very high electricity consumption, which needs to be taken into account.

Just checked, we have 26.3°C (79.3°F) in the dining room with a humidity level of 31%.

Thanks to the enthalpy exchanger in the ventilation system, these values are already quite good. We are very satisfied.

Lumpi_LE schrieb:

Something like this is great but has a very high power consumption, which needs to be taken into account.

Well, sometimes you have to choose the lesser of two evils ops:

26° wow...
At the beginning, we also often had it too warm while we were still adjusting the heating system. It never bothered me at home, but I was freezing everywhere else, which wasn’t very pleasant.
Now, I believe we have about 22° in the living room.