I bought and am remodeling a house built in the 1920’s with dirt floor vented crawlspace and an addition that was built in the 60’s had to tear out and replace the entire floor in the addition had bulk water flooding into crawl space under heavy rain and it had rotted the entire floor out i have since remedy that issue with exterior drains and fixed/ replaced and sealed blocks in the foundation. I am going to be putting down 10 mil poly on the dirt floor and looking to insulate the floor i seen an article on GBA or FHB that had foil faced polyiso on bottom of joist and batt insulation  in between is this best way to go about it?. The crawl space floor is about 6-8 inches from the bottom of joist for large portion of the house and foundation walls are 1-2 block high.  What are my options here? One corner of the house has good amount of room to get under there i was thinkin of insulating that corner and building little room to house my pressure tank and manifold for water along with pump for the septic these will be the only thing running in the crawlspace and will be confined to one side of the house. Any help and advice is appreciated. Thanks