ᐅ Vapor Barrier – Should You Tape Down the Staples?

Good evening,

Two weeks ago, the insulation was installed between the rafters, with the vapor retarder placed on top. The vapor retarder was stapled to the rafters. Shouldn't these areas also be sealed with Siga Sicrall?

I have been told that this was partly done in some passive houses. For our non-subsidized house, the blower door test was also very good without taping.

In principle, yes, because moisture can penetrate there and then reach the rafters or pass alongside them into the insulation, especially if the stapled areas tear or come loose. Nowadays, the more elegant hole-free solution is usually the double-sided adhesive tape method: a narrow double-sided tape is applied to the rafter, and then the membrane is fixed onto it. This is how we did it; it worked perfectly—quick, neat, and without holes. At the same time, this method is also supposed to have the advantage of sealing the screws used later for the counter battens by driving them through the adhesive layer.

However, to be honest, I don’t think there will be any problems if the stapled areas are not sealed afterwards, unless it’s in a genuine wet room.

Sorry, when you write “the membrane on the rafter,” this refers to an underlay membrane that protects the insulation from moisture coming from outside. (There is a regulation requiring the use of adhesive sealing tapes between the counter battens and the underlay membrane.) It is not the vapor barrier, which is installed on the interior side of the rafters.

DachbauKfm schrieb:
Sorry, when you say the membrane on the rafter, you mean an underlay membrane that protects the insulation from external moisture. (There is a regulation regarding the use of nail-sealing tapes between the counter battens and the underlay membrane) Not the vapor barrier, which is installed on the inside of the rafters.

No, it is really the vapor retarder. The underlay membrane is on the outside and the vapor retarder is on the inside. [emoji1]