OLD HRV ducting failing!! have you checked yours...
IF your HRV systems is more than 5 years old the ducting may need replacing.
Very easy to check
1. Is it becoming transparent
2. It has holes or tears in it
3. the ducting has collapsed or no longer holds a round shape.
If the ducting is in poor condition the system will not work properly, it is imperative that the ducting holds its round shape.
Supercell has a full range of ducting & you can also upgrade to insulated ducting.