If there are a number of large windows and glass doors on the road side, double glazing definitely helps. Use the glasses with different thickness and largest possible air gap in the middle to maximise noise dampening. We used to live on Princes Highway near traffic light which has quite a traffic all day long: tire noise, engine noise, and truck breaking noise. At night everything is a lot more audible. We retrofitted bed rooms sliding doors for the apartment with uPVC frame double glazed door and that was a big different. Don't go the route of clip on product, like Magnetite. They don't work as well as a proper double glazed windows and doors.

The prices sound fair especially considering that they include installation. Viridian have a variety of glass types that are specifically designed to deal with acoustic issues. Anything will be better than 4mm float glass. A reputable window manufacturer will be able to give you great advice on glass selection, if they can't find another one! If you really want to eliminate noise you would end up with 2 panes of glass about 100mm apart but it is unlikely you need to go that far (it is an uncommon solution).

you are super-patient!!! :) :) thank you :) I'm so sorry but I do actually have a couple MORE thoughts!! argh! there are just so many different options.... and this is a bit of an all consuming puzzle to try to solve. here they are: 1) study could become main bathroom - leaving new Bed 4 as per plan since it is bigger & a better size for guests. in this option, some area could be stolen from the study to boost ensuite size - even if it just made the ensuite 1 full metre. Ideally not requiring study window to change. 2) WC could potentially be separate either within this space OR at the back of the old kitchen (allowing for the remaining, longish hall wall to be shorter again) oklouise you may think some of these ideas are not very workable & I'd be so glad for your feedback & comment (and anyone else's comments as well), it's really so incredibly helpful - unbelievably helpful - to have everyone's input. i'd love recommendations on which ideas & options might work best for that balance between function & budget

answering your questions: change the sliding door to a bench height sliding window and use the salvaged sliding door in the western end of the dining room where the best entry position is for the deck, you MUST have a proper legal drains do not consider anything else...the drain pipe for the garage laundry can be on top of the concrete floor, behind the washing machine and through the sink cabinet and/or under built in storage and only needs a few cms not a whole floor and no stepped up area that you would see or trip over.. the laundry can't be in a separate room as there's not enough space for a separate laundry without compromising the size of the garage...a laundry cupboard 80 cm deep is enough for the washing machine (allowing for the drainage pipe) you could use the old line cupboard to store anything you want but it's not cost effective to change, the entry foyer is already as big as in many modern homes and there's generous flatpac biw space in the small study.... the family bathroom is 2380 x 2370 (ie the old study minus 1m for hall way and wall thickness and, arranged exactly as shown to allow for the wide window there should be space for a bath up to 1800 x 750, vanity about 1200 x 500 and shower space 1200 x 800 and leftover space makes the small linen cupboard with the door deliberately opening towards the shower to use the back of the door for hanging racks for towels and clothes....btw i understood your priority was maximizing separate sleeping rooms and minimising costs...my last plan has five separate sleeping rooms plus the lounge with sofa bed totalling sleeping places for at least 10 people plus the potential for bunks in the garage so you need to decide what is most important and where you're prepared to compromise