Why Does Condensation Form Under a Metal Roof?
People sometimes say:
“Metal roofs sweat.”
Metal does not create water.
Condensation happens when moisture in the air contacts a surface cold enough for the vapour to turn into liquid water.
Why Can Metal Make the Problem Visible?
Metal changes temperature relatively quickly.
During cold conditions, the underside of a metal roof can become cool.
If warm, moisture-laden air reaches that surface, condensation may form.
Where Does the Moisture Come From?
Possible sources include:
- Indoor humidity
- Air leakage
- Poor ventilation
- Construction moisture
The solution therefore starts with understanding how moisture is reaching the roof assembly.
Why Insulation Matters
Insulation helps manage heat flow.
But insulation alone does not stop uncontrolled air leakage.
A roof assembly may also need appropriate:
- Air control
- Vapour control
- Ventilation
depending on its design.
Does Every Metal Roof Need the Same Assembly?
No.
A residential attic with metal roofing behaves differently from an unconditioned agricultural building.
The correct approach depends on the complete building system.
Is Condensation the Same as a Roof Leak?
No.
Both can produce water.
But their causes are different.
A contractor should determine whether moisture comes from:
outside through a roofing defect
or
inside through condensation.
Fixing a Moisture Problem Starts With Finding Which Side the Water Came From.
Envirotech Exteriors can assess metal roofing together with attic and ventilation conditions when moisture appears beneath the roof.