Close in lattice areas under house?
This is a picture of my house. The home was built in 1907, has almost no insulation, and is located in central/south Texas. I was told by our HVAC person and a contractor that we should close in the areas under the house where the lattice is to help insulate. I was told by another contractor and a foundation person this wasn't necessary and that ventilation was more important. If I close it up I was thinking of only closing the North/South sides by adding a piece of plywood behind the lattice. What should we do about the area under the house?