ᐅ Wooden ceiling on the first floor with vapor barrier or vapor retarder

Hello forum members,

I am renovating the hallway on the first floor and then the attic.

When renewing the ceiling, I noticed there is a draft. To address this, I sealed the rafters with a vapor barrier. About 4 square meters (43 square feet) of ceiling area.
I know that a vapor barrier is not necessary when both rooms on either side are heated.

Could I still install the vapor barrier on both sides?
For the sake of airtightness?

I don’t know the roof insulation, as it will only be renewed in a few years. The house was built in 1992.

Best regards,
Edison

If the attic space beneath an insulated roof is sealed to the extent that air cannot circulate there, this is far from advantageous.