I live in central nj near the shore. I have a new furnace in a crawlspace. During October and November, my gas bills were $240 for the two months combined. All of a sudden, my Dec bill was $250. I keep the heat at 68-69. Recently sealed my ducts with mastic and started insulating them. I am hoping the bill is lower but am wondering how my bill got so high when the avg temp has been 40. Was thinking of bringing an hvac guy in to see what is wrong. Any thoughts? Thanks!