I am in the process of installing a heat pump in my 1200 square feet home getting rid of an oil boiler. I have the quotes and I am torn between two installers. My home currently has central air with round circular vents in the ceiling. The two installers agree that re-using the circular vents wouldnt be a good choice. One installer didnt do a load calculation and would leave the circular vents and install rectangular vents near the windows for better air flow. The other installer using a load calculation would use larger multi-directional vents in the same place as the circular vents and will adjust the air circulation in each room.
I am receiving conflicting advice when I compare the reasons from each vendor. I dont like the idea of leaving the circular vents and installing new ones. This would incur an additional cost to repair the ceiling. I really dont want my ceiling with 4 vents in each room. The installer impose that I go with incess lighting at a later time. But that has an additional cost. Please advise on the best to go as far as comfort and cost.
There is no "one bedroom equals x vents"
That is done by a load calculation of many factors.
To put directional vents (three way, two way) they will be most effective over heat loads like a window. The older style of circular vents throw a 360 degree (or close to it) pattern hence the centralizing.
Either will work, depends on your load. If you change them and the load is actually fine as is, that's an ascetic change. It'd be more worth your time to add insulation or better windows to decrese your overall load and re-calculate what size you actually need. My experience is you will be downsizing truthfully.
Buying a system is an expensive proposition. If you want it to last 20 + years you will need to consider other factors.