I recently purchased my first home, a three bedroom ranch with a finished basement in Rochester, NY. Ive began looking around the furnace and noticed that the "furnace exhaust" is being vented outside via 4" PVC that runs out the side of the house. In all other homes that ive seen, the furnace is vented out through the roof via the same pipe the hot water heater is vented through. Is it ok how it is? Should i vent it out the roof? can i use the 6 inch vent that the hot water heater vents out through? I appreciate your help.