These photos are two examples of homes with furnace vent stacks that need to be replaced. Both were inspected by my company, Magpie Property Inspections. The properties are located in Denver Colorado and Aurora Colorado respectively. Both homes are over 30 years old and these both appear to be original to the houses.
It is important to keep an eye on the vents stacks in your home for several reasons. First and foremost, these vents carry spent fuel and carbon monoxide from gas furnaces and hot water heaters during operation. Damage to the vents, or holes in the sides, may inhibit the vents from drafting correctly preventing the dangerous gasses produced during combustion from exiting the interior of the house properly. Any back draft or limited drafting can lead to a very serious health concern to those inside including dangerous levels of carbon monoxide gas inside.
In addition, vents in this condition are likely to leak at the sides or base allowing moisture into the attic, interior or down to the appliances. This can lead to wet rot and even the possibility of mold developing inside if undetected. Moisture in the heater unit can cause increased wear, a malfunction or damage requiring repair or replacement.
Lastly, as the stacks become brittle and old they become susceptible to wind and storm damage exposing the inside of the homes to interior wind, hail or water damage in the event of a serious storm. It should not be located within 10 feet of any inlet venting to the house, and at least 2 feet tall. Replacement of worn or damage vents and stacks is normally not very expensive and can be done by qualified roofing, HVAC or general contractors.