Improve Air Conditioning: Avoid These 5 Ductwork Design Jul 30, 2015DUCTWORK DESIGN MISTAKE #5: Lack of returns. To maintain balanced air pressure and air movement, your duct system needs return vents for air in the room to be pulled back into the HVAC system. Not providing enough returns is a common ductwork design flaw that leads to comfort complaints. 6 Tips for Good Ductwork Design Ductwork layout | HVAC Plans | Design elements - HVAC Wikipedia] The HVAC floor plan example "Ductwork layout" was created using the ConceptDraw DIAGRAM diagramming and vector drawing software extended with the HVAC Plans solution from the Building Plans area of ConceptDraw Solution Park. Hvac Duct Layout Drawing. ConceptDraw.