Older homes may not have floor insulation. It’s required in all new homes unless you have a sealed crawl space. It’s reconnected to have at least a R19 insulation valve “6 inch faced Batts” A home without floor insulation will add approximately 1/3 to your heating load. Example: A home with floor insulation that takes a 60,000 BTU furnace. The same home without floor insulation will need a 90,000 BTU furnace.