We recently purchased a home in San Jose, CA that was built in the 50s. I'm natively from a place with basements where the the furnace always is located. However, in our home here, the gas furnace and gas water heater are located in a small utility room (in the center of the house), which is accessible via a door inside a closet. I've noticed that this utility room has both a floor vent (into a vented crawl space) and a ceiling vent (into a vented attic). Although I am sure this is the safest way to go, is it necessary? It seems like a huge amount of heat escapes through the vent. Although the vents are separated from other rooms by 2 doors, it still seems like a lot of heat can escape under the doors. I'd love to close up these vents if it won't cause other problems. I know that open combustion devices need an air source, but does this need to be into cold spaces? Note that both the furnace and water heater are "normal" top venting (low efficiency) types. Thank you!