Upgrade to variable speed HVAC for zoning

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New Member
Mar 13, 2023
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Hi all,

My new house has 2 stories and 1 thermostat per floor and there's only 1 outdoor unit, so, I assume the air conditioning for first and second floor is handled by 1 single unit. The house already has ductworks. I want to zone my house like so :
  • Floor 1
    • Zone 1 : master bedroom and the bathroom attached to it, thermostat will be in the bedroom. 1 vent in bedroom and 1 vent in bathroom
    • Zone 2 : study room -> 1 vent
    • Zone 3 : family room + dining room + kitchen (open space without partition) around 4-5 vents
  • Floor 2
    • Zone 4 : bedroom 2 -> 1 vent
    • Zone 5 : bedroom 3 -> 1 vent
    • Zone 6 : bedroom 4 -> 1 vent
    • Zone 7 : bathroom 2 -> 1 vent
    • Zone 8 : game room -> 2 vents
Right now, I assume the house is already zoned to 2 zones -> first and second floor (judging from the separate thermostat each floor). So, my questions :
  • Assuming the HVAC is 2-speed and I want it to become variable speed, do I only need to replace the blower motor without needing to change anything else?
  • I just need to put wireless dampers in each branchings in the ductworks and we'll have "zones" already?
  • Once blower motor has been upgraded, I dont need to worry about static pressure (return vent) since blower can now adjust the power so if out of 8 zones, only 1 zone is requesting conditioned air, the blower will lower the power, therefore, no significant increase in static pressure
  • For now, I cant do heating in 1 zone and cooling in other zone, this would be impossible unless you have 2 ducts for each zone, one for heating and one for cooling. Is this correct?