Air Vent does not manufacture products for use on flat roofs. All of our products require a minimum 3/12 roof pitch. There are specific products available for flat roofs typically available through commercial roofing channels. Some Air Vent customers have built a curb on a flat roof with enough pitch that they can mount a power fan, for example. There is a product called a one-way breather that some contractors use on a flat roof. Checking the internet for “one-way breather vents” could likely yield more information. In situations where a flat roof ties into a sloped roof, it is important to be sure that there is an opening from the flat roof to the pitched roof. If there is, placing intake vents in the flat roof and allowing them to vent to the opening at the intersection with the sloped roof will allow an exhaust vent at the top of the sloped roof to draw from the intakes in the flat roof. (Here is an illustration.)