I don’t think I could tell you why but whoever built our apartment did not run any Heating plus A/C duct to the part dining room… It was an entirely insane move. It makes no sense whatsoever, however both of us did not have guests over for awhile because both of us did not want to put them in a cold dining room. Both of us could heat the dining room a little bit by just leaving the door wide open to that room, however both of us did not want our guests to have to leave the dining room door open, that would have been awkward for them plus the room was still not extremely warm even when both of us left the door open 24/7. My amazing husband thought about running some Heating plus A/C duct throughout the room, however he has not gotten the opportunity to do it yet! He has been super tied up at work, plus both of us cannot afford to hire an Heating and A/C service tech to do it. Both of us have been using a little electric fireplace in there for the time being. The problem with using the fireplace is that it is expensive. Both of us try to open our apartment up to those traveling through my section that have nowhere to stay or don’t want to have to pay for a hotel room. It is sort of a ministry of ours. Both of us have to have that dining room warmed up almost everyday, so it costs a lot of money to use that oil furnace 24/7. We are going to have to figure out something weird eventually, however for now, both of us are just using that fireplace plus hoping both of us have enough money to pay the electric bill at the end of each month.