After a roof replacement changed how a Houston home's attic was ventilated, the homeowner went to Reddit to decide whether to follow the roofer's advice to replace attic fans with ridge vents or the HVAC technician's advice to restore the fans because the attic ducts were sweating.

Here's what to know

"Not sure who to trust on this," they wrote. During an HVAC inspection, a technician noticed condensation on the ductwork and said the attic was not getting enough circulation.

Several commenters pushed back on that explanation. "Your HVAC guy is wrong," one HVAC engineer said. "Sweat on ducts is due to poor duct insulation, not airflow in the attic. If it's humid, and the surface of the duct is below the dewpoint, it's going to sweat regardless of whether there's a lot of air or a little air moving through the attic. Make sure those ducts are insulated properly and repair any damage to the insulation."

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More background

"The roofer is right, it is one or the other," one user wrote. "But for ridge vents to work correctly, you need to have your soffits opened. Did they open the soffits? That is what allows proper air flow to go up your roof line and out the ridge vent. Without that, ridge vents are useless."

Baffles (also known as rafter vents) can help direct that air up through the rafter bays and toward the ridge.

Commenters said performance can suffer if the intake route is obstructed. Some pointed out that soffit vents are sometimes clogged by insulation or sealed with paint, while another commenter warned that using attic fans alongside ridge vents can "short-circuit" ventilation by pulling air from the ridge and exhausting it before the attic is ventilated evenly.

Attic moisture can raise the risk of mold, reduce insulation performance, and force heating and cooling equipment to work harder. That can push bills higher at a time when many families are already looking for ways to make their homes more efficient and affordable.

What can be done?

Suggestions in the thread included checking attic ducts for inadequate or damaged insulation, making sure a vapor barrier is present, and confirming that soffit vents and attic baffles were added when the roof was redone. The homeowner also asked about options for old ductwork, and one commenter said solid ducts can be wrapped with insulation.

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Where can I learn more?

These stories explore the same kinds of questions, from attic fans and hot-climate cooling claims to ductwork issues and debates over efficient HVAC upgrades.

• Homeowners weighing roof changes asked whether attic fans cut energy bills or just shift heat.

• In Florida, HVAC pros said a viral device to save your AC was overhyped.

• Home efficiency experts say common HVAC myths stick households with expensive, outdated systems.

• In New Mexico, a homeowner considering a heat pump learned to do their own research first.

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