We build a house 1 year ago and when the temperature gets below 50 degrees outside we start getting cold air coming through 4 vents of our house. All vents are on the opposite side of the house than the furnace. The colder the outside temperature gets the more air we have dropping from the vents. This happens within 15 minutes of the furnace turning off and we usually have about 2 hours between cycles so you can imagine how cold the 2 rooms get until the air kicks on again. The company says our house is doing a convection thing and they said although they have only had this happen once or twice ever that it is a normal thing that happens. The bad thing is that the vents we get the cold air dropping from are directly over my bed and directly over my 4 year sons bed. Can anybody tell me if this is normal, should you have that much cold air coming out of your ducts? The duct work and furnace are in the attic.