Whether SS, aluminum or galvanized depends on the application. If you decide to vent atmospheric via a masonry chimney, it needs needs to be lined and allowances made for the furnace vent and proper draft. If she won't draft at times properly, you may have to add a powered exhaust vent. -Types of Chimneys, Vents and Connectors- PVC vent material is unsafe, even though supplied with the install kit (documentation contained in earlier post).. DIRECT VENT ensures proper exhaust/supply, low emissions and low operating cost.