adding a second extractor fan

[opps]

In the down stairs wc/shower room I have a 100mm thru wall Manrose exractor with a motion sensor (85m3/h)

For years this was sufficient until we replaced our combi boiler.

Now we are getting buckets of condensation on the aluminum framed double glazing and walls (one of which is exterior). The room is in a flat roofed extension.

I am trying to decide whether to:

a) upgrade to a larger fan with an airflow of 200+ m3/h or
b) add a second ceiling fan in the shower area that goes through the flat roof.

If I go for a) I will need to make a template for the core cutter given that I already have a 4" hole. I will also need to buy or hire the cutter

If I go for b) a ceiling mount I have to go straight up through the plasterboard and plywood/felt. There is no scope for horizontal ducting.

Which is considered the better option?

Thanks in advance.

 

[PrenticeBoyofDerry]

a.
To rebore hole, could well be worth filling it in, so your pilot drill can get a good surface to hole with.

 

[TicklyT]

Has changing the boiler reduced the ventilation in the shower room?

Whichever fan(s) you choose, an extractor fan won't extract anything unless there's sufficient ventilation to replenish the air in the room it's in.

If there isn't enough ventilation, two fans could fight each other, with each trying to draw air in against the flow from the other's exhaust.