I have a 1940 home newwer windows and doors blown in foam walls in my 2 story. my boiler runs almost 24/7 winter gas bills are $400- $500 per month. My boiler is 85% efficient 4 year old unit.I am currently installing cenral air system in ceiling and attic.is forced air cheaper to run than boiler heat? should I get rid of boiler system ? envey nieghbors when there furrnace runs 20 min of an hour while mine does not shut off when 20deg out here in ohio any advice? witch is more cost efficient?