Hi & welcome. Check the articals section of the site for "A better skirting idea" It was written by Mark, The owner if this site when he installed metal skirting on his home.
I think a few here have done concrete skirting also, perhaps they will add to this.
The formula for ventilation is 1 sq foot of vent per 100 sq foot of ground under the home. Greg
"If I can't fix it, I can screw it up so bad no one else can either."