Yes, louvres do 'leak' more than some other window types but they also allow for much more effective ventilation as they are around 95% open when versus an awning window which can be as low as 25% open. The big question is where are you? Tasmania or the NT? Generally the solution is to use them sparingly but your designer will be able to advise on how many and where to place them.

Louvre windows are one of the most expensive window types, mainly because of all the glass edges that all need to ground smooth. If your glass blades are in good condition and the size you need, I think you could talk to Breezeway about just getting new louvre clips in the right colour and reinstall them at a substantial saving.

if they're traditional old fashioned steel and glass louvres you're probably looking at a major renovation that could also involve rebuilding walls and replacing internal and external wall lining and insulation.....you can find prices for some standard sized window and glass doors on websites for the major hardware stores but you'll need a builder or carpenter to install them as it's not a straightforward job for an inexperienced amateur and it's sometimes better to rebuild walls and have windows custom made to suit ...

Yes it would look odd to install them later as the flyscreen frame will be a different colour. Best to have them included in the window design when you order the window for a much neater result. https://www.trendwindows.com.au/quantum/quantum-lourve-window/ Best of luck, Dr Retro of Dr Retro House Calls