[faithfulfrank]

The main problem one sees is that when they blow in the insulation, they can cover up the air path from the soffits into the attic, thus stopping the needed air flow.
To prevent this, you use either cardboard, plastic or foam baffles to insure this does not happen. When doing this one should make sure you get them long enough so if years later they add more insulation they will not be covered up.

A good builder will staple ruler like guides around the ceiling joists to insure that when the insulation is blown you get even coverage to the correct amount you are paying for.

In older homes where the soffit was originally wood, then covered with perforated vinyl or aluminum soffit one needs to check that the wood was removed or at least cut into first to make sure you DO have air flow. I have seen nice looking perforated soffit installed over solid wood, you you THINK you have air flow, when you do not.

I like to see a ratio of 1 square foot of ventilation space for each 150 foot of attic. One should also note that it is VERY common in Florida to see decorative side vents installed over solid wall sheathing. You THINK you have ventilation there when you only have a decoration.

Frank