What type of vent cover?

[Gozogozo]

Hi I had a detached garage rebuilt as an insulated garden study plus store but no airbricks or ventilation built in. I have asked my builder to put in some ventilation as he is returning to do the snagging & he said that he can use a core drill to make a 120mm hole & that I should buy 2 louvre vents of approx 9" size to fit on either side.
I seem to remember Piglet John suggesting that such holes are angled slightly and that cowl vent covers are better but I can't find that thread on my phone & I am quite possibly mixed up in whether applicable here...
Any help gratefully received!

Have a look on Screwfix at cowl vents, which I prefer for extractor fans and tumbledriers, they have a one-way flap against draughts, and the cowl keeps rain out.

But I think a simple brown (to blend in with brickwork) grille on the outside will be better in your case, and a white one on the inside, or a hit and miss vent inside, which you can adjust or close in windy weather. They will be in the same ventilation section. Look out for the size as many are 100mm which would be too small. Don't leave them permanently closed.

Also look at tlc-direct which may have a better range.

p.s. you will also need some plastic duct to line the hole to prevent the wall getting damp. Same section.

Hi PigletJohn thanks for your advice - job done per your suggestions.
Sorry I couldn't remember my fifty hundredth password change to get on & thank you before!