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Ductwork sizing, calculation and design for efficiency – HVAC Basics + full worked example

How to design a duct system. In this video we’ll be learning how to size and design a ductwork for efficiency. Includes a full worked example as well as using CFD simulations to optimise the performance and efficiency. FREE SimScale account (

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45 thoughts on “Ductwork sizing, calculation and design for efficiency – HVAC Basics + full worked example

  1. You need to be a part of a contest for one of the greatest blogs on the net.
    I am going to recommend this website!

  2. Yeah this is pretty cool. Im a sheet metal apprentice, specializing in ductwork for commercial jobs. Interesting to see how the ductwork I make is designed and such. Great video!

  3. Amazing video, thank you. I noticed in the video (14.39) you are inputting the data into the interpellation website. that you input in Q11 value 0.14. Should it had been 0.15? (LOL) Its just me and no big deal. It kept me on my toes…so very helpful on your part. Love the videos…..THANK YOU

  4. can you also do a comparison of using one centralized hvac system versus mini-split units for the same size of a house having four bedroom and two floors. tks.

  5. Ok my question which is better, a furnace register that blows upward or one that blows across the floor as I have noticed blowing across the floor has it problems and furniture can block flow and create cold spots especially in smaller rooms so I guess my question is do I heat from top down if that makes sense(my old house has registers in the wall and blow across the floor)

  6. Sohrab:
    Ques 4:-
    Coefficient of pressure values of fittings like
    It will varies or fixed according to CFM

    Ques 1:-
    During calculating static pressure only critical path will be taken or not ?

    Ques 3:-
    In formula
    F= friction factor or friction head loss

    Ques 2:-
    we will calculate all the VCD OR only critical path?

  7. Ok this is what I want to get into. Sounds really interesting. I currently have this oversized fan in my house. The duct looks waay too small and the noise is the biggest problem. I was thinking to increase the size of the duct to lower the noise but will try first to use these calculations to see if it would make any losses in terms of cooling. Do you (or anybody here in comment section) have any advices on how to lower the noise without loosing too much on cooling?
    Thank you in advance.

  8. Hay engineer……
    I have one hanger which has 7 room and 3 big hole…….
    How can manage and I select either split air condition and Centralaized cooling system.
    Which system is efficient for me…..plz note that all air condition is not working all the time unless the big holes.

  9. The new job has the customer hire an engineer to design the system. Or, charge them to design the system from plans. I personally work with a lot of engineers and they do this all the time. If the customer wants a free design move on.

  10. HI, I am a beginner, ducting for 2 story with basement in South Philadelphia ,
    the land / house space is Wide 16 ' x Long 40 ' (feets) ,
    what is the ducting dimension / size for main duct , [ 8"x16 ] or [ 8"x24" ] or….. is better ?
    because I do not know how to calculate it .

    thank you

  11. Do we size the unit by heat load or volume flow rate at main duct "A"? I am running into a situation that unit capacity is sufficient to the heat load, but the calculated volume flow rate at main duct "A" is more than the unit CFM. What do I do in this case?

  12. The Engineering Mindset :- I have have not under stand Fitting example H : Outlet direction 2-Bend (Time 15:1015:48). Calculated Velocity ratio and Area ratio, then based on that get coefficient 0.364 from bend table. My question is why don't we applied that coefficient value in pressure loss equation {pressure loss=coefficient x density x velocity Sq. / 2}. instead of that directly mention that vale 0.364 as fitting loss in Direction G-I. Anyone
    please help

  13. Question: Why are two story homes, fitted with 2 units, but not ducted to accommodate 'convection'? Heat going up, cold falling. Returns are on the same floors as ducts for each unit. WHY?

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