Summary
Most RV-style exhaust fans are integrated in a typical 14" roof vent. Fantastic is a popular brand of fan. These devices require a separate external shroud to allow use during rain. MaxxAir is a popular manufacturer for these covers.
Maxx came out with a single unit with integrated cover and fan, eliminating the need for two products. Another benefit, though not significant for our use, is a lower profile on the roof, when closed.
Two exhaust fans are used. One is mounted in the rear, equipment compartment, and is controlled by an integrated thermostat. The primary purpose of this unit is to provide over-heat protection in hot weather. During the cooling/AC season the rear compartment is sealed off from the work area, and air conditioning does not cool the rear area.
A second unit is in the grooming area and controlled manually. Ventilation is required year-round to eliminate moisture generated by drying wet animals. This puts additional load on the furnace, but there is no practical alternative.
