The outside humidity is 96%. The attic humidity is at 60%. When the attic fans turn on, the humidity in the attic begins to increase. Is this normal?
The attic insulation is batts, not blown-in. There are baffles installed as well. I cannot tell if air flow is moving through the baffles.
The hotter air in the attic can hold more water than the cooler air outside, so for the same absolute amount of water-in-air, the warmer/hotter attic has lower relative humidity than the cooler outside air with the same absolute amount of water-in-air. When the fans pull in cooler outside air, the relative humidity will rise as the attic cools off. The absolute amount of water-in-air is unchanged.
One measure of the absolute amount of water-in-air is the dew-point. In a ventilated attic, the dew-point will be the same as the outside air, because the outside air moves through the attic via ventilation.
Logic would say it is normal.
When the fans turn on they are drawing in the outside air.
Outside air is higher in humidity than attic air.
Low humidity air is being replaced with higher humidity air.
Unless there is another device to change humidity, you simply are exchanging the air. You are not changing the humidity in the air, simply mixing it.
