Keeping outside vent when replacing vent holes with extractor fan?

Hennymore

One bathroom has those passive vent holes through the wall, with a grille on the outside.

I want to have an extractor fan installed.

I would like to keep the current outside grille, because it's above a conservatory and would probably require scaffolding to get at from the outside.

Could our installer simply put in the extractor fan on the inside where the vent holes were, and plaster over any remaining vent holes not covered by the fan? Keeping the outside grille and just using the old hole-through-the-wall rather than installing ducting?

Would this be reasonable, or a bad idea? If so, why?

If it would be a bad idea, what would you recommend instead given these circumstances?

Owain_Moneysaver

An air brick often does not have enough clear airflow for an extractor fan.

You can get fan and tumble dryer ducts that install from the inside, often labelled for high-rise buildings.

Hennymore

Thank you, Owain. While the inside is just holes in the wall (presumably a painted-over airbrick), the outside is currently a metal grille. Assuming there's not an airbrick behind it, would it then be fine?

Great to know there are ones that install from the inside. Cheers!

Owain_Moneysaver

Depends on the holes in the grille, and also whether it's sleeved right from the outside to the inside or leaks into the wall cavity.

Hennymore

Owain_Moneysaver wrote: »

Depends on the holes in the grille, and also whether it's sleeved right from the outside to the inside or leaks into the wall cavity.

Thank you. I don't believe the walls are cavity, but I'll check before we install the fan.

This is what the grille looks like from outside:

Furts

I appreciate it is going off topic, but why is the wall so wet? That is a healthy crop of moss growing there. Not good to see, and It cannot be doing any good to your mortar.

Hennymore

No worries, appreciate it. Photographed through a wet conservatory glass roof, so that explains the drops Agree about the moss. Recently moved in and it’s on the todo list.