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  1. #1
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    Louvers on ducts to balance flow

    I'm currently getting quotes from several A/C contractors for a split system A/C & furnace. Master Bed (2 registers)/Bath (2 registers) in particular heats up/cools down faster than the other rooms. One contractor wants to install louvers (so 4 total) in the attic on the duct work to cut down flow to the bed/bath. He discouraged using resisters due to whistling and leakage (through and around the entire register). I mentioned this to another contactor and he said to buy good quality registers from Lowes and just use those to control flow. He also said I would have to go in the attic multiple times per year to change them as the seasons change. Anyone have any opinions on this issue? Thanks!!!

  2. #2
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    Get an air balancing contractor in to install dampers at the main trunk, then set the required air flow for each room.

  3. #3
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    As Sherm would say, horsehockey. To use registers to balance airflow is just a problem. Usually they howl if you have them partially shut.

    Putting balancing dampers on the takeoffs in the attic is the correct way to do it. They would need a nicely sized duct system as when you throttle back air to 1 or 2 runs, you better have plenty of duct for it to go down or those runs could get a bit noisy or you restrict airflow and overheat the furnace or freeze the A/C.

    4 registers better be a pretty small system if just a master suite. Bigger is NOT better!

  4. #4
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    If using registers they must be OBD ( Opposed Blade Damper ) Parallel dampers are not to be used for balancing use butterfly damper in the attic in this situation--- Some scenarios do not allow for dampers in the attic IE a direct tap off of a plenum to register.

  5. #5
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    If those rooms have too much air flow for both heating and cooling, then I recommend dampers at the take-offs. Your contractor is correct that regulating flow at the registers will be noisy.
    As has been stated by others, you'll need to make certain that the total volume of air flow is not reduced to the point that the equipment does not work properly.
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