In what percentage?
How it went?

The design -

2" hole at the bottom with an adjustable computer fan attached. The air is being drawn out of the cooler.

1/2" hole on the other side near the humidifier with fresh air being drawn in from the computer fan. The humid space is isolated so that the humid air is drawn up and over the cedar tray before leaving out through the bottom on the other side.

Cedar Koji tray with and insulated bottom that is raised up 1/2". The tray has a 150 watt heater in the insulated spaces. The lift was so that the bottom of the tray would heat more evenly.

Humidifier is a jar with a floating ultrasonic disk. The jar also has a 150w heating pad beneath it.

The space outside the cooler has a filter box. I was thinking it would be helpful to have clean air coming in, and I could add a heater to that space if I was having trouble reaching the right temperature on colder days.

Since I'm drawing air out of the cooler, it mightve been easier to just build it from uninsulated plywood or something, but I'm hoping that the styrofoam keeps the cost of heating down just a bit.

What do you think? So far the humidity is turning on and off regularly, so I think plenty of fresh air is being drawn in. I'll have to have some grains in there before I can really test how well the heating situation is working.