Dear All – my home was built in 1985. The basement includes a crawl space under the kitchen, family room, and laundry area – this makes up about half of the basement. 
The crawl space has 3 vents (the size of a cement foundation block), two vents are to the outside and one vent is into the garage. What is the current thinking on this type of vent? Please note these do not close. 
I would ultimately like to air seal the crawl space and to insulate it. There is currently fiberglass batt insulation between the joists but it is failing and therefore time to change it. 
thank you for your feedback / input.
regards 
chris