I recently had a dual zone heating system installed in my basement. For the past two months I have not had the heat on in the basement at all and it has been hot as the temperature has been in the 70's and the mechanical room where the furnace is in the 80's. All the vents are closed in the basement but the temperature does not go down. The temperature outside has been cold as it has been in the single digits or teens on some days. Upstairs it is set to 68 degrees and the furnace is running constantly. Is it normal that the basement would be this hot with the heat off down there and the vents closed or is something wrong? My last heating bill was over $300. I am concerned that I am overheating my basement and cannot find a way to keep heat from escaping down there. Thanks for any insight anyone can offer.