The HRV will work the same as a exhaust fan to lower the
relative humidity, the HRV just recovers most of the energy used to heat the air in the house before it is exhausted while using no more energy to run. Even here in Calgary the outside humidity is 60% but that is at a temperature of less than 5 degrees. That same air at 20 degrees would be less than 10% relative humidity. Warm air has a greater capacity to hold moisture, Thus, it would contain 10% of the total capacity of water that it could hold before the water condensed out once warmed to room temperature. So even at 86% RH outside, you would gain significant drying of the inside air.
Here is an interesting chart to see just how much change in relative humidity warming the air makes.
http://www.skuttle.com/humid.html