Warm air escaping from a duct into a cold attic can create condensation and encourage mold growth.
Attic insulation condensation.
In the real world this means moist air from your house coming into contact with the underside of your cold roof tiles or the side of your water tank etc.
Signs of condensation in the attic may include the following.
Insulation is responsible for keeping warm air inside your living space and out of the attic where it can lead to condensation.
Applying mastic gum to the duct joints and adding an r6 layer of insulation around your sheet metal ducts goes a long way toward protecting your attic and ceiling.
Moisture forming on the glass window panes or other flat surfaces.
Check your ventilation system.
For a more detailed explanation see my article on condensation in buildings.
And the same factors that cause attic condensation problems also cause ice build up on roof edges which can lead to ice damming.
To save time and better pinpoint the problem you can hire a professional to inspect your insulation and fill any gaps that might be letting warm air into the space.
This condensation can form droplets of water and accumulate into the insulation below.
It is common for poorly vented and insulated attics to develop attic condensation.
Next take a look at your attic ventilation.
It can also cause mold to grow on roof sheathing trusses rafters and ceiling floor.
Traces where water has trickled down the walls.
Condensation will form in your attic if warm moisture laden air comes into contact with a cold surface.