What are my ducts actually made of?
Ducts in a Cape Coral home are usually one of three materials: flexible duct, a lightweight tube with a wire coil inside wrapped in insulation; ductboard, rigid fiberglass board formed into a box shape; or sheet metal, rigid galvanized steel or aluminum. Most homes mix more than one, sheet metal or ductboard near the air handler in a trunk line, flex duct running out to individual rooms through the attic. Each material fails differently and needs a different kind of attention.
Flex Duct: The Silver Tube Running Through Most Attics
Flexible duct is the ribbed, silver tube most people picture when they think of ductwork: an inner wire coil wrapped in plastic, surrounded by insulation, and covered in an outer vapor barrier. It's light, it bends around obstacles in a tight attic, and it's faster and cheaper to install than rigid alternatives, which is why it shows up so often on the branch runs carrying air out to individual rooms.
Its weak point is exactly what makes it convenient: flexibility. A run that's kinked, crushed under something stored in the attic, or stretched too tight between two points restricts the air moving through it, sometimes badly, without ever showing an obvious sign from inside the house. The connections at each end, where flex duct clamps onto a metal collar or a register boot, are also where most of its leaks tend to start.
Ductboard: A Box Built Straight Out of Rigid Insulation
Ductboard is rigid fiberglass board, faced with foil on the outside, cut and folded into a box shape and taped or stapled together at the seams. Instead of insulation wrapped around a separate duct, the board itself is the duct and the insulation at the same time, which made it a popular, economical choice for trunk lines and plenums for decades.
Its seams are the part worth knowing about. Every joint where two pieces of board meet is only as good as the tape sealing it, and that tape can dry out and lift over the years, especially in an attic that runs hot for most of the year. The interior surface is also fibrous rather than smooth metal, which is why ductboard generally isn't a candidate for the kind of aggressive mechanical duct cleaning that rigid metal can tolerate without damage.
Sheet Metal: The Rigid Backbone Near the Air Handler
Sheet metal, usually galvanized steel or aluminum, is the rigid material most often found closest to the air handler itself: main trunk lines and plenums, where the most air is moving and the pressure runs highest in the whole system. It holds its shape under pressure in a way neither flex duct nor ductboard can match, which is exactly why it tends to show up at the point in the system doing the heaviest lifting.
Sheet metal doesn't crush or sag the way flex duct can, and its smooth interior surface handles cleaning better than ductboard's fibrous one. Its own weak point is the seams and joints where sections connect, which need a proper mastic or foil-tape seal to stay airtight. A metal duct that looks solid from the outside can still be leaking air at every joint along its length.
Why It's Worth Knowing Which One You've Got
Most homes end up with more than one of these three materials in the same system: sheet metal or ductboard handling the trunk near the air handler, flex duct branching out to bedrooms and living spaces through the attic. Each one fails in its own way and gets diagnosed differently, which is why a technician looking at duct leaks or an airflow problem checks the material at hand rather than assuming one fix covers all three.
It also shapes what's reasonable to attempt versus what calls for a professional look, since knowing the material at least tells you what kind of problem is even possible in that particular run before deciding what happens next. A thorough AC repair visit accounts for which materials are actually running through the attic before diagnosing a leak or an airflow complaint, instead of treating every duct system the same.
Not Sure What's Actually Running Through Your Attic?
Call or text (239) 350-5234. Tyler, Guiseppi, or someone from their team can identify the duct materials in your system as part of a flat $150 service call.