Thank you everyone for all your help and advice! Yes, we live in an inland part of Southern Australia that is very chilly in winter and exceedingly hot in summer. So efficiency is a very important part of our build. From the picture you added Louise, I think a "coffered" ceiling looks like what I would call an "up lift". I'm glad to have a second on that option ;) The picture looked good, and could defiantly be an option over the dining table I think. Thanks jbantick I looked up "scissor trusses" and they look like a great idea as well. I'm just not sure how they would run. From the entry across the dining area (N to S) or across the whole length of the 3 zones E to W ? The middle of the roof line (running E to W) doesn't run in the middle of the living zones (if that make sense) as it stretches across a hall way on the south side. If it ran this way would it look a bit off centre? How did you in vision it? Thanks for your thoughts guys.

Ours never leaked. We'd installed it, then lived in the house 7yr. The previous skylight was leaking badly when we bought the house, it was one of those plastic dome ones- revolting. It was pretty easy to work out why the flashing had corroded in the old skylight- it was chock full of leaf compost. After that- every year the husband would get up and clean the roof gutters and the gutter of the skylight. Like anything regular maintenance will prevent leaks. I'm not sure what the rules are with cyclone-zones. Velux are made from toughened glass. I'm sure their website would give you this detail. Yeah- they get dirty, then it rains and they are clean again! At one stage we got a little bit of lichen growing, but then in Summer it died and just went away! The dirt/dust never bothered us....it's not like you walk around staring up all the time. It doesn't lessen the impact of the extra light and height.

Judging by the plan, the photos and your comments it appears that too much heat is coming in from high light glazing (clerestory windows) into the lounge and dining areas. Both rooms will be cold in winter because the direct heat from these windows is not enough and not absorbed in an thermal mass and they do not have ground level windows or glazed doors facing north. The elevated floor means that it is cold under the house so heating in winter goes down as well as up. The roof would lack adequate insulation due to the period in which the house was built. The roof tiles probably have another 15 years maybe a bit more so it is costly to insulate from the top (i.e. taking roof tiles off adding insulation then putting roof tiles back in again. The colour of them is contributing a lot to the heat. So what to do. - add external shading device to the highlight glazing, maybe timber battens 40 x 40 at 20mm spacings. This will block direct sunlight within the shading season. That helps to reduce heat intact and see how you go. If that does not work then - add a rigid foam core board to the underside of the timber ceiling, e.g. Foilboard which is 20mm thick r 2, then install a 12mm plywood ceiling lining under this. That way you retain the timber rafter ceilings but also one that has a light coloured (hoop pine ply) timber in between. (Note this is costly) - big gains in heat loss is achieved with underfloor insulation. Try r3 bulk squeezed tightly between the floor joists. Then you can plan for the future with the following - change glass in windows and glazed doors to a low e glass - install insulation into the cavity of the external walls using a company called envirowall. - replace roof tiles with a light coloured metal roof, replace the existing roof battens with a 100 x 40 batten so that you can install a 100mm thick anticon insulation. All of the above costs money and if you don't do it then it costs money to burn energy to keep the living rooms between 21 to 27 degrees year round (what we consider comfortable) so if it tough to decide what to do or not. As an alternative For about 40k you could spend 30 of it on solar cells, and an awesome battery (Tesla powerwall 2) and buy some wall mounted ac units. But that would be kicking the can down the road. But sometimes you have no choice. Good luck

You're right about the insulation up against electric wiring being a potential fire risk. It's commonly done in Australia and unfortunately there aren't many regulations about it, but I don't personally think it's best practice. More importantly though - while adding insulation is always a good idea, it probably won't make too much difference to how warm or cold your house gets. Do you have any sort of heating system in your home? It's really the only way to keep your house warm, especially if you have minimal insulation. Hydronic radiator panels would be a fairly easy retrofit if you have a timber floor, and you'll never be cold again. If it's getting too warm in summer, usually the culprit is too much direct sun getting in. Consider a shade or awning over your north facing windows to reduce some of the direct sunlight getting in. Ceiling fans also make a big difference, and adequate ventilation.