Hi Zobadi. I'm also building in Sydney (& have lived here for ~40 years) so some of my research may help you.
It does depend somewhat on who will be living there - what they will be comfortable with and how much they are home etc. Although Sydney winters are very mild compared to the UK, most of our houses aren't built well to keep out the cold so it doesn't feel mild sitting in your house. Both summer & winter need to be addressed.
Thermal Mass: - remember if you put carpet or timber, etc over your concrete slab you will lose much of the effectiveness of the thermal mass. To really utilize that thermal mass you need to have polished concrete floors as you said, or tile it - which may be cheaper.
Another way to add thermal mass, is adding phase-change material into the ceiling or walls - see here - http://www.phasechange.com.au/
Heating:
I agree with the others that said Hydronics are not suitable/efficient for Sydney as they have can take a couple of days to heat up or cool down. So if you have a warm spell, you can't really turn it down to save money & energy. I've also read that electric underfloor heating is expensive to install and to run.
I've read that gas heating is the most efficient, reverse cycle air con the second most efficient. But ducted air-con is very inefficient if you just want to heat or cool one room because even if you have it zoned, it still only has 1 inlet.
Cooling:
It's good you plan to use ceiling fans. Check these ones out: http://aeratron.org/
At the end of this year they'll be bringout out a larger & a smaller version and a built-in light option.
You may need air-con as well on occasion, when a fan just ain't enough, especially when it's humid. We're putting Aeratron fans in every room, phase-change or thermal mass, insulation, passive design. Not sure if we'll need air-con or not, or which rooms, but after deciding against ducted, found that split-systems are easy to install after the build - I think you just need a power point near the unit(?). So we'll wait until we've lived there a bit & then decide if we need air-con or not.
Insulation:
In Sydney, the recommendation regarding insulation is that insulation in the roof is most important. R4 is recommended. It's also recommended for walls of course. If you go with the timber frame, the thickest insulation that will fit is R2.5 - unless you get something much more expensive that batts.
We didn't look into SIPs very much as they are more expensive than brick veneer. There's alot of new/newish ways to construct walls like SIP's, which all claim to be economical to build with because they go up so quick, but ask any regular builder to use them and they'll charge more - often just because they haven't used them before. Also, in our case, we would have had an issue with getting insurance if we used SIP's as we are building in a Flame Zone, but that probably isn't an issue in the inner west.
Eaves & Windows:
Check with your builder regarding the 500mm eaves - whether he's included the gutter in that 500mm, because the gutter adds 10 to 15cm to the width of the eave. So an eave built to 500, could effectively be 650mm with gutter.
If you need eaves of over 1m, you must be having floor to ceiling windows? There's a few issues with floor to ceiling windows to consider:
* If you have the biggest eave you can, you still won't block all direct sun in summer but you will block too much sun in winter.
* Even double-glazing is much less efficient than an insulated brick veneer wall, so too much of the heat gained on a sunny winter day is lost in the evening. And for the week it's cold & not sunny, you're just loosing heat.
* You can't put any furniture there. With a window elevation of 900mm you have the option of placing a lounge chair, side table, or small book-case etc under the window.
* If you are considering double-glazing, it will be much more affordable with a smaller window.
* Do you really want to clean all that glass?
There's a bit of a trend now to have windows go all the way to the ceiling or bottom of the eaves. This means that the top of the window is always shaded - and you have a view of the eaves. It's better to stick to the more traditional way of having the top of your window = the top of your internal doors - usually ~2.1m. This should give you a bit more gap between the top of the window and the bottom of the eave.
The ideal window size (for standard clear glazing) is based on floor area of the room:
North facing windows & concrete slab - up to 25% of room floor area - so if your room is 20 sqm, your window should be no more than 5sqm (eg. 2.4 x 2.1 - pretty big)
North facing with no thermal mass - up to 20% of room floor area
South & East facing should ideally be less than 15% of room floor area, and West facing less than 10%. But then total window area for the whole house should be 10-15% of total home floor area for north-facing on concrete, up to 10% on timber floor, less than 5% each for south & east facing, and less than 3% for west facing windows, ideally.
Presumably double-glazed windows could be a bit bigger on the north & south, whereas if you want bigger windows on the east or west they should be low-e or toned to reduce solar heat gain.
Eaves wider than ~600mm are likely to block too much sun in winter. I think I remember a problem with the eave recommendations given on yourhome. Please check out this site - http://www.susdesign.com/overhang_annual/index.php - it's a really great online tool for calculating eave & window size. The latitude for Sydney is 33.9 degrees south. Note that the overhang spacing is from top of the window to bottom of eave - not ceiling height. Eaves are usually lower than the ceiling height - by how much depends on the slope of the roof and the width of the eave. As an example, my new eaves, which will be 600mm (plus gutter) will be about 10cm below the ceiling (my roof slope is 10 deg). You'll see from this calculator that if your window is due north, and not floor to ceiling, it's pretty easy to block all direct sun in summer and maximize winter sun even with an 500mm eave. If your window is 10 or 20 degrees off north, it becomes more of a compromise between ideal winter & summer conditions.
Double-glazing:
When I rang window companies to see how much extra double glazing would be, most of them said "Why would you want that? You don't need that in Sydney", which I thought was pretty stupid. Of course double glazing will make the house more comfortable and reduce energy required to heat & air-con', the only question is whether the initial outlay outweighs the savings in energy costs. I've seen calculations for this but there are too many variable factors including what energy will cost in the future (or if you'll be making your own, how much energy you'll actually use on heating & cooling and this depends on what you use and how you use it. I use mine alot because I work from home all day & night. People who are only home in the evening would use alot less and therefore take longer to recoup costs of double-glazing, insulation etc. We can't afford to double-glaze our whole house (I think it's more expensive for us because we need 6mm toughened glass and to get that in double glazing required commercial sized framing) but I think it will be worthwhile for the room I spend most of the day in.
Almost as good as double glazing for keeping heat in, is floor to ceiling, thick curtains with a pelmet - and they have to be wider than the window and be fitted close to the window to minimize gaps.
Low-E is not very expensive so it's worthwhile if you have windows facing east or west that you can't shade from direct sun in summer. Don't get it for the north unless you really want a window much too big to shade and care more about shading in summer than gaining warmth & light in winter.
You mentioned shades for keeping heat out - I'm not sure what you mean. Blinds on the inside of windows will reduce heat coming in but much less so than an aluminium shutter on the outside, but these aren't cheap and only work when they are closed, blocking out all light too. Suitable if you close them before going to work to stop the house heating up while you're out, not so suitable for keep sun out while you're home. Best price I got was from Shutterworld.com.au eg ~$1000 for 1.5 x 1.8m window. Or you may mean some kind of sun-hood - like a mini eave built directly over the window? If you get these make sure it doesn't shade too much in winter and that it allows hot air to pass through it - you don't want it trapping hot air under it, beside your window.
Don't forget to plan for capturing cooling breezes. Find out what direction your cooling breezes will come from in summer. For us it's from the east - from the distant ocean, with the occasional southerly. But for you if the harbour is north, you might get cool breezes from that direction. To make the most of cool breezes you need windows open on that side, though they don't to be big, and you need an opening (window or door) on the other side of the room so the breeze can pass through and out the other side of the house. If the breeze only has a way in, there is too much air pressure (or something) and will just go around the outside of your house instead.
The thing with breezes and thermal mass & curtains is that they only benefit you if you use them properly - closing windows & curtains on summer mornings, opening them to cool the house down at the end of the day.
Sorry if I've gone on too long!
Posted Wednesday 30 Jul 2014 @ 2:02:37 am from IP
# 
