Duct repair in Menlo Park, Atherton and Portola Valley usually starts with a complaint about one part of the house: the back bedroom that never cools, the family room that stays chilly, the hallway register that barely blows. Where ducts run through an attic or crawlspace, the cause is often a run that has come loose, been crushed, or started leaking at its joints. Finding which takes a measurement and a trip into the attic, not a bigger system.
Common duct problems and what fixes them
| What you notice | Likely duct problem | Typical repair |
|---|---|---|
| One room gets almost no air | Run disconnected at the register boot or the plenum | Reconnect, fasten and seal the run |
| Weak air at several registers on one side | Crushed or kinked flex duct, collapsed inner liner | Re-route or replace the section |
| Warm, dusty attic smell when the system starts | Split or open return pulling attic air | Seal or replace the return |
| Wet spots under ducts in summer | Missing or torn insulation on supply runs | Re-insulate the run |
| One zone too hot or too cold | Stuck zone damper or a disconnected trunk | Damper repair or reconnection |
| System runs long, bills climb | Leaky joints along the whole system | Sealing with mastic, then a leakage test |
How the problem is found
Leakage testing. A calibrated fan pressurizes the duct system with the registers covered and measures how much air escapes. That gives a starting number and shows whether the whole system needs sealing or one run is the culprit.
Room-by-room airflow. Air is measured at each supply register and compared across rooms, along with static pressure at the air handler. A room getting a fraction of what its neighbors get points to that run.
Following the run. Then someone goes into the attic or crawlspace and traces the duct from the plenum to the register, looking for a loose boot, a section flattened under stored boxes or a stray footstep, torn insulation and failed tape.
Older ducts in attics and crawlspaces
Many Menlo Park homes are more than 50 years old, and their ducts have lived through decades of attic heat, re-roofing, rewiring and storage. Original sheet-metal runs tend to fail at the joints, where old cloth tape has dried out and fallen off. Flex duct added in later remodels sags between hangers, kinks at tight turns and loses its outer jacket. Crawlspace ducts under ranch houses get knocked loose by plumbing and cable work and by animals looking for shelter.
Some duct wrap and joint tape from the mid-century era contained asbestos. If the material looks original and fibrous, it should be tested by a qualified lab before anyone cuts or disturbs it. If we see material like that, we tell you before any work is scheduled.
Large homes, zones and long runs
Large homes in Atherton often run two or more systems, or one system split into zones by motorized dampers. Long trunk lines through attics and basements lose more air, and more heat, before they reach the far rooms. A damper stuck closed can look exactly like a disconnected duct, so damper operation is checked from the zone panel before anyone goes after the ductwork itself. Each system is tested on its own.
Foothill homes, dust and smoke
Portola Valley homes on hillside lots often have long runs to a wing or a lower level. Return leaks there pull dust and pollen from the attic or crawlspace into the house. On wildfire-smoke days, a leaky return can also draw smoky attic air indoors even with every window shut. Sealing the return side is one of the most useful things you can do before the next smoke season.
Repair a section or replace the run
Repair makes sense when the damage is local: a disconnected boot, one crushed section, a few leaking joints on otherwise sound metal duct. Replacement makes sense when flex duct is brittle along its length, insulation is coming off in sheets, or a run was undersized from the start. If most of the system is in that state, a full re-duct belongs with central air installation planning. Either way, the written estimate should separate the immediate repair from follow-up work and optional upgrades.
Cost and time
Most duct repairs fall between $200 and $1,500 and take 2 to 6 hours. One reconnected run near the attic hatch is at the low end. Replacing several sections in a tight crawlspace, re-insulating long runs or reworking a zone damper costs more; access often matters as much as materials. Larger replacements may need a permit, and the estimate should say whether one is included. After the work, airflow is checked again at the affected registers.
Before the visit
Write down which rooms are uncomfortable and when, and whether anything changed recently: a re-roof, solar panels, new wiring or storage in the attic. A photo of the attic hatch or crawlspace entry helps plan the visit. To see the whole house, not only the ducts, an energy audit adds a blower door and thermal imaging. If the ducts are sound but dirty, duct cleaning explains when that is worth doing, and our ductwork warning signs post covers what to look for yourself.