Roof tile vents: membrane needs cutting?

[keyzjh]

We are getting a new roof installed with breathable membrane under the roof tiles.

I'm using one of these in-line tile vents: https://klober.co.uk/roof-ventilation/roof-vents/in-line-tile-vents/p/15x9-tile-vent

Do I need to cut a hole in the membrane directly underneath the vent? I assume not as the membrane is air-permeable?

 

[RandomGrinch]

Do I need to cut a hole in the membrane directly underneath the vent?

Read the instructions?

 

[freddiemercurystwin]

Of course you do, as above.

 

[keyzjh]

I did read the instructions but roofer said he doesn't cut it usually. Thanks for the confirmation guys!

 

[freddiemercurystwin]

There's a big difference between the movement of vapour through a breathable membrane and a physical hole that allows actual airflow. You roofer's a dope.