My house is only 11 years old with two fireplaces. One of them is extremely cold. It feels like cold air is rushing in all around the fireplace unit. It has all the tile around the mantel and hearth cold. The outside had wood siding and I've had it bricked as well. I don't know where all that air is getting into the fireplace cavity. I've called a fireplace sales/service store but they don't think they can help, but suggested that there might not be any insulation inside the frame. Any ideas on what might be the problem, how I can find out or who to call for help?