Duct Insulation

Cooled air leaves your evaporator coil around 55 degrees. Then it travels through a space that is 155 degrees. Every foot of that trip is a heat exchange working against you, and the only thing standing between the two temperatures is the insulation wrapped around the duct. Thin it, compress it, or tear it, and the air arriving at your farthest register is no longer 55 degrees. It is 62. The system runs longer to make up the difference, and in July you pay for the difference twice, once in runtime and once in wear.

R-8 versus what is actually up there

Current practice puts supply ducts in an unconditioned Arizona attic at R-8. A large share of Valley housing stock is still running R-4.2 flex, which was legal when it went in and delivers barely half the resistance. The jacket tells you which you have, since the R-value is printed on the outer wrap. Past the number, condition is what matters. Insulation compresses wherever a run rests on a truss chord or wherever somebody knelt on it to reach a water heater. It tears at tight bends. Sunlight through a gable vent chalks and splits the outer jacket, and once that vapor barrier opens, the fiberglass inside slumps away from the core. What you are left with is an uninsulated duct wearing a sleeve.

The fix depends on what is there. Runs with a sound core and a failed jacket get re-wrapped in R-8 with the seams sealed and the vapor barrier closed, because an open seam during monsoon season lets humid attic air reach cold metal and condense, which puts water above your drywall. Bare or thin plenums and trunk lines get wrapped too. The plenum is a large surface at the coldest point in the system, and it is frequently the single biggest gain available in the attic. Where the flex itself has degraded, adding wrap to a bad duct is throwing good material at a lost cause, and new R-8 flex is the honest answer.

What insulation will not do

It will not stop leaks. If your system is losing twenty percent of its air through open seams and disconnected boots, wrapping the duct warmer does nothing about volume you never receive. That is duct sealing, and it almost always goes first. Insulation also will not fix a duct that is undersized for the room it serves. And if the attic itself is thin on insulation, adding attic insulation lowers the temperature the ducts are fighting, which makes the wrap work better and cools the ceiling below at the same time. We will tell you which of the three buys the most comfort per dollar in your house, and it is not always the one we happen to be standing next to.

You feel this work as delivered temperature, which is the only measurement that matters to you. Put a thermometer in the farthest supply register before and after, and the gap between the two readings is the job. Upstairs bedrooms fed by long runs across hot attic space feel it most, which is a large part of why upstairs is always hotter. Flat-rate price before we start, 1-year labor warranty, and a straight answer about what we found. Call (480) 863-5855.