Duct Sealing

Your air conditioner does not care where the cold air goes. It just makes it. If the duct joints in your 155-degree attic are open, a third of what you paid for gets dumped above the ceiling instead of into the room. Studies and our own field measurements land in the same place: a typical existing home loses 20 to 30 percent of its conditioned air to duct leakage. On a Phoenix August bill, that is real money, every month, forever. Duct sealing is the fix that pays you back. It is a completely different job from duct cleaning, which addresses air quality and does nothing for your energy use.

Where the leaks actually are

Not in the middle of the flex runs. Leaks hide at connections. The plenum where the trunk meets the air handler is the worst offender in Valley homes, because it is the highest pressure point in the system and it was often sealed with cloth duct tape in 2003. That tape is now a brittle ring of dried adhesive. Next are the boots, the metal boxes behind your ceiling registers, which are frequently set into drywall with a half-inch gap all the way around. Then take-offs, branch splits, and any spot where a previous tech opened the system and closed it back up in a hurry. We inspect all of it during an attic duct inspection before we quote anything.

What we seal with, and why it matters

Cloth duct tape does not seal ducts. In an attic that swings from 60 degrees in January to 155 degrees in July, the adhesive cooks off in a couple of seasons and the seam opens right back up. We use water-based mastic troweled onto joints and reinforced with mesh where the gap is wide, plus UL-181 rated foil tape where mastic is not practical. Boots get sealed to the drywall or ceiling plane, not just to the duct. For homes where the connections are buried and unreachable, we can discuss an interior aerosol sealing approach that seals from inside the duct, though on most single-story Phoenix homes with an accessible attic, hands-on mastic work is cheaper and just as effective.

We measure before and after. That means static pressure readings, register airflow, and a documented leakage comparison so you can see what changed instead of taking our word for it. If you want the full diagnostic picture first, airflow testing tells us whether leakage is your actual problem or whether the system is undersized, the return is starved, or the design is wrong. Sealing a duct system that has crushed and torn runs is a waste, so we will tell you when duct repair or full duct replacement is the honest answer instead.

Here is when we tell people not to buy this. If your ducts are original R-4.2 flex from the eighties, sun-baked and separating at every collar, sealing them is putting a bandage on a rotten limb. If your system already tests tight, you do not need us. And if the complaint is one hot bedroom rather than a high bill, the cause is more likely balance or design, covered in hot and cold room solutions. When sealing is the right call, it is one of the best returns in the whole HVAC world. Flat-rate price quoted before we start, one-year labor warranty, and we clean up after ourselves. Call (480) 863-5855 or request an estimate.