ᐅ How to ventilate a walk-in attic?

Hello.

We have the following roof structure:
52mm (2 inches) exterior insulation above the rafters and 280mm (11 inches) insulation between the rafters.

A retractable loft ladder will be installed at the collar beam level. The access is only for inspection and for storing items that will not be needed for years, such as leftover tiles, etc.
So, a lot of moisture is unlikely to be introduced.

Do I still need ventilation for the attic space? The carpenter suggests using humidity-controlled vents, but the construction manager thinks it’s unnecessary.

Thank you for your advice.

It is unnecessary if basic principles of building physics are considered.

A cold floor experiences significant temperature fluctuations over 24 hours due to solar radiation. This means the air near the cold floor can hold varying amounts of moisture; therefore, the air by the cold floor should be dry enough to prevent condensation even at night.

This means the retractable staircase should be kept open only as briefly as possible to avoid any issues on the floor.

Storing tiles in the attic? Is your attic floor usually made of wood? Please keep in mind that the load should generally not exceed 100kg to 150kg (220 to 330 lbs).

We can store over 1000kg per m2 (204.8 lbs per ft2) on our collar beams.

Regarding the topic: I would definitely recommend including ventilation. From my own experience, unplanned moisture infiltration can occur, especially during the construction phase. Also, the vapor barrier is never completely airtight.

We have two Velux windows installed, and the ridge line is open.