Manually Adjustable Humidistat/Thermostat Control for EGV/ERV Power VentsThe GAF Master Flow adjustable Humidistat Thermostat Combo works with GAF Master Flow EGV ERV Series Vents. It works in harmony with your powered vent to help control damaging moisture. It also reduces heat accumulation and buildup in your attic. And is fully adjustable for varying climates. Helps reduce the likelihood of damaging moisture or heat accumulation in your attic Designed for use with GAF Master Flow EGV ERV series power vents Fully