When do you notice that the controlled residential ventilation system is working?

In an air-to-air heat exchanger, the heat transfer can theoretically only occur up to the point where the supply and exhaust air have approximately the same temperature, or am I mistaken? That would be the case at 5 degrees Celsius and the parameters mentioned above.

The supply air at the outlet (which is, of course, significantly higher at such low outside temperatures due to further heat uptake within the building envelope) or directly behind the heat exchanger?

Hello.

Here is an excerpt from a manufacturer's product description. The controlled residential ventilation should have approval for passive houses (which I believe most do):

"...To be awarded the Passive House certificate, a demanding testing procedure must be passed. The ventilation unit must achieve a minimum supply air temperature of 16.5°C without additional equipment even at an outside air temperature of -10°C. This is important because passive houses do not require additional heating surfaces on exterior components. Therefore, the supply air temperature must be limited at the lower end to avoid uncomfortable cold air drafts. In addition, the total electrical power consumption of the ventilation unit in operating states intended for passive houses must not exceed 0.45 W/(m³/h) of supplied air volume flow. ..."

Best regards

Hi, and how do they manage that if additional devices (e.g. heating element) as described in the text are not allowed? Simply overflowing supply and exhaust air can't work... Although the thing is called a heat exchanger, it's not as if the temperatures of supply and exhaust air are simply "exchanged" and the supply air after the [WT] almost has the temperature of the exhaust air. Without electric or similar reheating, it's a mystery to me.

@ Cascada

What you describe is, in my opinion, the only permissible "heating system" for passive houses. Installed in conventional house construction, you will have a lot of fun with the upcoming annual electricity bill.

Therefore only conditionally comparable with the controlled residential ventilation with heat recovery discussed in this thread

Rhenish greetings

Construction expert, on the go

@ Cascada

What you describe is, in my opinion, the only permissible "heating system" for passive houses. Installed in conventional house construction, you will have a lot of fun with the upcoming annual electricity bill.

Therefore only comparably applicable with the controlled residential ventilation with heat recovery discussed in this thread to a limited extent

Rhenish regards

Bauexperte, on the go

Hi,

I paid significantly less than €500 for my brine heat pump in 2013 (01.01.-31.12.) (or rather about 2200 kWh). Not passive, but KfW70 – and a very cold region. The supply air temperature of the controlled residential ventilation never fell into the single-digit degree range in winter. At minus 20 degrees I don't know for sure, of course, because the supply air is strongly reduced here (no electric preheater).

Best regards

Hi,
...The supply air temperature of the controlled residential ventilation never was in the single-digit degree range in winter...
Regards

Hello Cascada,
directly behind the heat exchanger or at the outlet in the living space? Those are two different things.
Regards,
100

Hello Cascada, directly behind the WT or at the outlet in the living area? Those are two different things. Best regards, 100

If you look at the installation and airflow volumes of the supply and exhaust air ducts... it should be clear that there is no significant temperature difference in the ducts between the controlled residential ventilation unit and the air outlet. Nevertheless, the fresh air at the room outlet has temperatures well above the 'average temperature' between indoor and outdoor air – simply because a heat exchanger is not just a heat conduction membrane where the air of both ducts flows past in the same direction. The component in many systems is not called a 'counterflow heat exchanger' without reason – the volume flows run in opposite directions. So the inlet duct of the supply air enters the heat exchanger at the end where the outlet duct of the exhaust air exits. Thus, the exhaust air, which has been cooled down to this point, can still warm up the even colder supply air. And the warmed supply air exits the heat exchanger at the end where the slightly warmer exhaust air enters. This causes the supply air to be warmed up to this point, and increasingly from warmer exhaust air over the length of the heat exchanger.

Best regards I.