A common problem when people 'go cheap' on regular HVAC systems is over pressurization.

Example the structure is fairly tight and a roof top packaged unit with a manual/motorized fresh air damper with no relief is used.

Relief can be barometric, or a powered exhaust fan right in the packaged unit or, the dumbest one, a scheme that uses motorized dampers to try and regulate the pressure.

Without the relief, It likes to blow doors open and in a cold climate it forces moisture out through the building walls. Besides a hard time closing doors another symptom is frozen locks.

This type of pressurization happens with a manual/motorized fresh air damper for upwards to 25% outside air.

In summer time with framed construction 2 Pa pf positive pressure with respect to the outside,tends to reverse infiltration and air leaves the structure. The mechanics of infiltration change with the season, in particular stack effect.

Continuous negative pressures of 2 Pa in humid climates has been documented as causing significant water damage in hotel/motel walls in the Southern United States.

Sometimes minimal fresh air to the space under pressure, and then exhaust being drawn from the areas surrounding the 'positive zone' works as well.

There are 'many ways to skin a cat' and the advice to get a design specialist, and better yet the customer to hire this specialist is good advice.