I own a thirty year old A frame that has been remodeled. The house is expensive to heat and cool, I don't know if the funnace was installed correctly and , or proper attic ventalation. Is there a diagram or insructions of how this system should be installed? It is a Ducane model# SG10B30075. I know I have some insulation issues but the unit is not that old and should be more eficient.