Yes and No. Yes, if the appliance can overcome the increased static pressure and still deliver the required amount of cfm needed to condition the space. No, if the appliance cfm delivery is limited and was determined by using round sheet metal, therefore requiring you to increase the flex diameter by one or two sizes. Use our flexible duct calculator to see the differences in static pressure between round sheet metal and flexible duct. As always, use a large radius when making bends in flex duct.