I have been looking into extraction rates for fitting a powerful through- the-wall extractor fan for a utility room.
Having looked at airflow rates and identified a ( so-called) "industrial" fan as the way to go it occured to me that the external grille might have an impact on the extraction rate.
Is one kind of grille better than another? I would think that the ones with gravity flaps will allow better airflow than (say) the fixed grid with a flyscreen behind it. But maybe I am just overthinking it!
