Install a masonry chimney, metal double-wall chimney or another type of manufactured chimney in your home if there is not one already. If one is already installed in your home, have its outer seal inspected for air leaks and repair any that are discovered.
Replace single-walled venting components with double-walled venting components. New, high-efficiency furnaces produce combustion byproducts at a much lower temperature than older models; these cooler byproducts can create hazardous condensation in furnace venting. Using double-walled ventilation helps mitigate the temperature differences between the inside and outside of the vents that create moisture.
Install fireclay, masonry liner or a retrofitted metal flue liner on the inside of your furnace's ventilation chimney. This final step to properly venting a high-efficiency furnace ensures that your chimney is lined with a material that can resist the natural corrosion that will occur from exposure to your furnace's combustion byproducts.