Lower indoor temperature after commissioning Controlled ventilation system with heat recovery

Hello everyone,

on Thursday, our controlled residential ventilation (Vaillant recoVair 260 E with heat recovery) was put into operation. We have an indoor thermometer and since the commissioning, the temperature is about 1 (maybe even a bit more) degree colder than before. It feels noticeably "fresher" in all rooms (also in the unheated ones). My question is, can the heat recovery not sufficiently warm the incoming air? Did you also experience such an effect? I mean, it’s understandable because there is a constant air exchange, but the consequence would be to heat more, and wouldn’t that contradict the energy efficiency advantage of passive houses?

Thanks for your opinions.

Did you also have such an effect?

No, absolutely not. But I would have really pushed my heating engineer then. That's what heat recovery is for - maybe your air exchange is too high or heat recovery is not working.

My question is, can the heat recovery not sufficiently warm the incoming air?

No, of course it cannot, the heat recovery only recovers a certain amount of heat partially. What is lost is called ventilation losses and is taken into account.

Did you also have such an effect?

Yes, of course, physics is the same for everyone. You simply coordinate the heating and ventilation with each other and that's it.

With controlled residential ventilation, the air simply seems "fresher" because it actually is, and that is unusual.

I mean, it would be understandable because a constant air exchange takes place, but the consequence would be having to heat more and wouldn't that contradict the advantage of passive houses regarding energy efficiency?

No, absolutely nothing contradicts here. You don't have to "heat more," only enough to compensate for all heat losses caused by thermal bridges, ventilation, walls, windows, roof, etc.

Since commissioning, the temperature is about 1 (maybe a little more) degree colder than before.
It is noticeably "fresher" in all rooms (also in the unheated ones).

The effect probably does not come from the controlled residential ventilation but simply from the unheated rooms, which increase the heating load, and the heated rooms simply cannot maintain the temperature because they also have to "carry along" the unheated rooms.

Hi,
if your system has a bypass for the heat recovery (so you can pull cool air into the house at night during summer), check if it’s not accidentally still open. We had the same with our system once and wondered why the air from the ventilation ducts felt so cold.

Best regards,

Andreas

Hi,
if your system has a bypass for heat recovery (so that you can draw cool air into the house at night in summer), check if it is still accidentally open. We had the same with our system once and wondered why the air from the ventilation ducts felt so cold.

Best regards,

Andreas

Yes, there is such a bypass, I can check again. But it should actually not be effective at the current temperatures.

Measure the temperature at the valve with an IR thermometer, preferably where there is a short pipe run from the [Kontrollierte-Wohnraumlüftung]. Where is the [Kontrollierte-Wohnraumlüftung] located?