Roof and water
Ventilated roof
housing school office industrial building
It is a two-layer roof with an air cavity between them. Air enters at the edges and leaves through the ridge, carrying the heat away.
What it solves
The outer layer receives the sun and the moving air removes that heat before it reaches the ceiling or the slab. In hot, humid climates it also helps dry the moisture that forms under the metal sheet.
Today
Leave continuous air inlets at the eave and an outlet at the ridge, protected with insect mesh. A radiant barrier or insulation under the metal sheet is advisable.
Common mistake
Closing the cavity at the edges, so that the air stands still and heat builds up.
Tomorrow
In heat waves the ventilated cavity separates the sun from the room where people sleep. It is a health improvement that can be made on existing metal roofs.
Fact In a test in Oman, a second skin with a 0.4 m air gap lowered indoor air temperature by 4.7 °C compared with an unprotected roof.
Where it comes from
- 1Jean Prouvé’s prefabricated tropical house (Maison Tropicale) Congo and West Africa, 1949 to 1951
Aluminum prototype with a two-layer roof and a ventilation system designed against the heat. - 2Queenslander house Queensland, Australia, since the 1840s
Rotating ventilators on the metal roof draw hot air out of the roof space.
Masters
- Diébédo Francis Kéré Gando Primary School, Burkina Faso, 2001
He separates a metal roof from an adobe ceiling and lets air flow between them. The classrooms are up to six degrees cooler than under the metal sheet alone.
Appears in the routes
See also
Also in Roof and water
Diagrams and texts by LDB Arquitectura. They are shared under the CC BY 4.0 license, which allows them to be used and adapted with credit to the source.