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Balanced vs Positive Pressure Home Ventilation System - Halswell

I have been getting quotes for a positive pressure system under the other job listing. I'd like to get quotes for a balanced pressure ventilation system for comparison. The details are: - four bedroom single level house - 189 m2, normal internal height, see attached plan - double glazed window (Low-E) on power coated aluminium joinery - accessible roof cavity for installation - no roof airflow restriction expected due to its construction (see photos) and two passive vents on the north side - existing power in the roof for an alarm system - one large heat pump in living room and one small one in master bedroom - heat pumps generate about 10kw combined heat, another 2-3km from plug-in heats in two smaller bedrooms that are normally used - not generally trying to heat lounge, study, spare bedroom (#2 on the plan) - openings to roof are limited to the range hood, exhaust fans in bathroom, ensuite, and laundry Main reasons: Air tightness was improved in the last couple of years for energy efficiency. Windows are now double glazed (lost small trickle vents on opening sashes), having replaced open down lights with closed LED lights. As such an increase in relative humidity level has been observed as well as some condensation. We do generally run exhaust fans in kitchen, bathrooms, and laundry, as well as opening windows regularly. Having looked into the differences between a positive pressure and a balanced system, I am of a view that a positive system should work fine at a cost of losing some heat but provide better control of retaining heat in the rooms being used at the time by opening/closing doors and using individual heat pumps/heaters. I do recognise advantages of a balance pressure system. To be certain, I was asking for a positive system with an upgrade-able path to a balanced system in the other job, which I'm still evaluating. It is my understanding that the ability to upgrade a positive system is potentially increasing costs of a positive system and making the final balanced system more expensive if I do take the upgrade. I'm now trying to make a up front decision between a positive vs balanced. Given I don’t think there is too much of a problem to start with, I’m interested in wide adjustments of controlling the amount of air being replaced. That is I would like to programme the system to minimum air change per hour required for the 189m2 internal space. I do appreciate technical details to make an informed decision. For example, fan (metric size, noise level, AC vs DC motor, set vs variable speed, wattage, m3/hr performance, inline mixed flow or centrifugal, rated hours, etc.), filter type (rating, inline vs sock), ducting size/type, control system working parameters (temperature, humidity), etc.