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Heating &Air Conditioning
The best way to design the airflow in a house is to do a Room by Room Manual J8 load calculation. This calculation includes the number of people in each room, activity level, what equipment, window size, window type, window direction, wall height, ceiling type and many other factors. This method is the hardest and takes the most time but develops the optimum system. The optimum system transfers the air to the extremities of each room and doesn't interfere with The airflow in a duct must be a certain velocity so that it doesn't stagnate(too low) or too fast (too much noise). Many contractors put in the same size ducts to each room and put dampers in them. Mold buildup occurs, improper velocities don't distribute the air correctly and things like wet grilles and higher humidity in the house can occur.
The modern mylar coated flex ducts are much better sealed than the old rigid metal ducts and don't transmit noise from room to room like metal ducts.
Please email Rick at firstname.lastname@example.org with any suggestions and comments.
update June 2007