The specific volume from the p-chart is for dry air only.
Its units tell you "cubic feet per pound of dry air"
The chart also gives specific humidity, and the units are "pounds of water per pound of dry air" or 'grains of water per pound of dry air" with a 7000 grains making a pound.
The specific volume gives how many cubic feet hold one pound of dry air, plus however much water. A specific volume given say '13.33 cubic feet per pound of dry air', tells you there is one pound of air in 13.33 cubic feet, but there is also water vapour in that 13.33 cubic feet.
If you want the true density of the moist air, then you need to add the mass of water vapour, the specific humidty to that one pound, then divide by the cubic feet in the specific volume.
The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.