A ventilated roof doesn't just keep water out: it keeps summer heat out and winter moisture away, letting a thread of air run beneath the tiles — from eave to ridge, all year round.
The ventilated pitched roof is a double-skin roof: beneath the tile covering runs a continuous air gap that, by the stack effect, enters cool at the eave and rises to the ridge. In summer it carries away the heat the sun pours onto the tiles, so the attic stays liveable; in winter it clears moisture and keeps the insulation dry, so it performs as specified and lasts. It is the reference roof of good contemporary building: protected insulation, a longer-lived covering, no hidden condensation.
click a beat · arrow keys ← → walk the site · dashed pauses are the chemistry at work
The detail of the craftthe continuous vapour check
Lay the boarding on the roof structure and roll out the vapour check on the warm side, with taped joints and upstands at walls and penetrations.
You lose the roof at the vapour check, not at the tiles: one open joint there and in January the insulation drips on you.site notebook — editorial synthesis
The roof's engine
Cool air enters at the eave, warms under the tiles and rises to the ridge on its own: no fan, just physics. In summer it removes heat, in winter moisture.
Schematic section, not to scale. The recommended ventilation section (of the order of 550–800 cm² per metre of eave, per UNI 9460) must be checked case by case against pitch length and slope.
The two skins
The covering is the first skin: it stops almost all the water. The breathable membrane is the second: it catches the little that gets through and drains it, but lets the insulation's vapour rise into the gap.
The membrane is not a luxury: it is what keeps the roof “ventilated” even on a day of driving rain, when a little water always gets past the covering.
Yes: the insulation stops the heat, but the air gap removes it before it enters and keeps the insulation dry. Without it, the insulation performs worse in summer and lasts less.
Usually 5–10 cm, more on long or shallow pitches. What matters most is that it stays continuous and clear from eave to ridge: the minimum section is sized per UNI 9460, described here in its logic, not reproduced.
The micro-ventilated roof has only the under-tile batten (a few centimetres): it dries the covering but does not remove the insulation's heat. The truly ventilated roof has the air gap above the insulation, with an eave inlet and a ridge outlet.
Yes: instead of the timber deck you start from the slab, in the same order — vapour check, insulation, breathable membrane and double battening above to form the gap.