How do you increase humidity with HRV system?
You cannot actively increase humidity with an HRV, at least during the cold months. The dial control allows you to run the unit as needed to reduce humidity by exchanging more moist indoor air with dry outdoor air. If you'd like to raise humidity you need to actually introduce moisture into your home.
A standalone humidifier in an appropriate location has done well for me in the past if you wish to avoid the expense of a whole-house unit. Place it where the air movement won't create discomfort and where the HVAC system will help circulate and distribute moisture.
By the way, you should not settle on a fixed RH for the entire winter season. You want to vary it depending on the outdoor temperature to avoid excessive moisture buildup and to prevent discomfort. 35% is quite low if it's 50 degrees F. outside, and may be high if it's -30F.


Outdoor temperature over 50˚F, indoor humidity levels shouldn’t exceed 50%
Outdoor temperature over 20˚F, indoor humidity levels shouldn’t exceed 40%
Outdoor temperature between 10˚F and 20˚F, indoor humidity levels shouldn’t exceed 35%
Outdoor temperature between 0˚F and 10˚F, indoor humidity levels shouldn’t exceed 30%
Outdoor temperature between -10˚F and 0˚F, indoor humidity levels shouldn’t exceed 25%
Outdoor temperature between -20˚F and -10˚F, indoor humidity levels shouldn’t exceed 20%
Outdoor temperature at -20˚F or lower, indoor humidity levels shouldn’t exceed 15%

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