News & Insights


Flex Duct Study After 10 Years of Use

Carl Christianson

Study of flex ducting removed from a system after 10 years of use. How much can duct sealing matter? I hear this question quite a lot when trying to explain to homeowners the benefits of duct testing and sealing. When most people consider their HVAC needs their mind somehow easily focuses on the equipment side of the equation. Furnaces and air handlers are efficient at one thing only, conditioning air and sending it downstream. Most of these systems have some sort of filtration system that helps to reduce the contamination of the air delivered. Adding electronic air cleaners and specialized filters can help a system to deliver air with less contaminates. While clean conditioned air principals are known to have a direct link to health , one should consider that the benefits of adding filters and cleaners only works when the system is sealed and in good condition. If a system has flex ducting you are more likely to have difficulty getting clean air within your home. Flex ducting is a easy and less expensive way to install air runs to a house but it is important to remember that flex ducting is known to have a lifespan to it. While manufacturers fail to put a timeline on their ductwork for lifespan, anyone who has spent time within a crawlspace has seen the effects of repeated heating and cooling on the plastic liners within a flex duct system. While the outside of the flex duct may appear in good standing order, there is only one way to tell of the interior liner has been compromised, removal and inspection.

Here is a photo of the interior of a flex duct that was recently removed from a system. The flex appeared to be in great condition on the exterior but our initial testing of the system showed such poor results that we started removing the ductwork to check. The flex duct in the photo was installed new less than 10 years ago when a new high efficiency furnace replaced the old house furnace. A new trunk line for the system was installed and new flex duct was added to deliver air to the floor registers.
The above photo shows the deterioration of the inner lining on the flex duct. What is seen is the fiberglass insulation that lines the duct and has been blowing through the house since the inner liner deteriorated. The second photo is the actual floor register with all the contamination dust and debris from just below the retrofitted register. Imagine this junk blowing through your house for 10 years.