@wayne For hydronics talk to Gary Flood at the Enter Shop. They are in Melbourne but he has installers everywhere. http://www.enter-shop.com.au/ Alternatively Alex at AJs Plumbing http://www.ajsplumbing.com.au/ We generally do in-slab hydronics but have also done it inside a rammed earth wall (at our office so feel free to come and look) and underneath a timber floor (several times including in our office). Insulation is critical. In a slab make sure you insulate the slab edge as well as the underside. When we talk of hydronics we generally use heat pumps to create the hot water (it's free to run if powered by PV). You mentioned wetback stoves (wood powered heating). In my view timber is only a viable option in rural settings. In (sub)urban settings the particulate pollution is a serious health issue and there is a fair chance that at some stage woodstoves will not be permitted by urban Councils. You finished by talking of ducted air conditioning. Regardless of the technology used to generate the heat/coolth, ducted systems are inherently inefficient and, in my view, should be avoided at all costs. The heat pumps can be great but the principle of pushing heated air around requires pump energy (you have to move large volumes of air). Almost all residential installations have flexiduct (not rigid as in commercial offices), the ductwork (aside from a study showing 80% of them did not meet the Australian Standard insulation code) due to its flexi-nature has lots and lots of curves and bends all of which increase the need for pump energy. This is why is it not possible to get a rated systems as you can with a split system; it is totally dependant on installation quality. You also need to be mindful of condensation issues in ductwork as heated air passes through relatively cold roof spaces, again quality of ductwork can be a big factor here.

As Australias largest supplier of hydronic heating, we have been providing Australian homes with stylish, safe and comfortable hydronic heating and cooling solutions. As exclusive stockists of an extensive range of premium products, we ensure that all homes can enjoy the benefits of a low carbon, energy efficient system. We have just released an industry leading guide on Underfloor Heating, that contains information for both homeowners and installers, I believe the content within would be the perfect for many commenters on this post. If you're unsure on how to proceed with your project I recommend you take full advantage of our personalised consultation service, available for both homeowners and installers. Using the latest design software and coupled with the expertise of our Customer Service Team, you can rest easy knowing that we’ll design a bespoke solution that delivers superior comfort that is also environmentally friendly and energy efficient. If you would like a copy please email me on sophieo@huntheat.com.au, alternatively head to our blog to download a copy: Hunt Heating Blog

HI All - for some reason my lengthy reply a few minutes ago was deleted :-(. I put so much thought into it! So here it goes again. Basically a big thank you to you Houzzers. MB your subfloor ventilation sounds great and Im glad it's fixing the problem so simply. The reason why Im trying for a whirligig solution is that I favour a passive system, however if it doesn't work I'll look into what you suggest Siriuskey - yes to some kind of kit. I've already contacted a guy on Gumtree selling grannykit frames - he says for something to my specifications would be about $4000 for the steel frame alone. Would need to check engineering details - and the liveable sheds you've linked me to seem to have that all checked. Although getting a local Chippie to frame it all up on site - as Twos Co suggests - is probably the most economical option Two's Co - thanks for the feedback and the excellent checklist of processes. I've covered most of the concerns though - I've got the DA based on my own flimsy plans. Because it's relatively small, I was going to work with the builder directly and over-engineer it. I've since engaged an architect to do some handsketches and draft specs, which will be signed off by a structural engineer. It's basically a portal frame independent structure, with a 3 degree pitch skillion roof. The house was rewired and the wires you can see are non-live looms waiting for the extension! The sewer is not connected and that part was never plumbed in. There's good rear lane access, but for the purposes of getting concrete in, I'll most likely get a concrete pump from the front of the house - for $180 per hour they will save time and make the concreting much easier. The existing trench I got dug in because I had an excavator on site installing those lovely large concrete blocks you can see, for the retaining wall (500kg each). But that was 7 weeks ago, and the excavation has got too large, and I worked out for a very similar cost I can make the extension 1m wider, so why not. The existing trench I can fill in with the demolition rubble, compact, and filled with any fill waste. Two's Company, I'm on the fence about removing the existing Bedroom 3. If I thought it wouldn't add to the costs too much, I'd do it. One advantage is that I could then make the whole 9m long extension (Option 2) around 150 - 300mm higher, (ie a step up from the existing house) and thus avoid too much excavation and a potential pond. To answer your question about damp and moisture, the whole house is facing a hill with 7 degree slope, and fixing this has been the main aim of the retaining wall, however the runoff is only likely to increase in coming years. anyway here are a few photos. The site is still so messy because the demolition only happened 2 days ago - Im still tidying up....

Here you go, siriuskey. This plan is not quite accurate. It seems changes were made in the initial build - mainly removing the raked ceiling (disappointing! I would have liked it!) and changing the 09.18 window in the garage to a sliding door located closer to the store room and laundry (thankfully, as there's no direct exit from the laundry). Some sliding doors have also been changed to hinged doors (the one from laundry to garage, from master bedroom to ensuite, and into Bed 2. What is marked 'patio' is actually a gorgeous covered veranda with feature timber ceiling and lovely planter boxes all along the edge instead of a railing. The carport has been transformed to a beautiful outdoor living area with a spa just behind it and a feature timber ceiling, though the floor is still exposed aggregate which will have to be sealed over so it's smooth for mopping. Overall, we love the house, except for the kitchen and the laundry and bathroom décor. I'm also disappointed there is no bath tub and hoping we can install one in the main bathroom and I'd like a small wash basin in the main WC, but drainage is an issue in houses built on concrete slabs when you want to rearrange things. I wanted to put a sink in the store room also, when converting to a butler's pantry, but again drainage is a question. Have no idea yet how to improve the bathroom décor. Currently there are very plain mocha coloured tiles floor to ceiling. The vanities will have doors two-pac coated, be topped with stone and have new basins and taps fitted. The walls have me perplexed. I'd like to add some features, and I hate tiles in showers. We plan to put a wall-mounted clothes line outside the store room and enclose with slatted aluminium screening (as that is the front entrance - but I don't like the thought of having to walk the full length of the house and further to get to the clothes line!) As we have only one car, we plan to divide the garage, partition in front of half the door and convert half the garage to a music room for my hubby. I hoped to put sliding shoji screens or similar across in front of the laundry cabinets so it looks more like a passageway into his music room. The biggest issue is the kitchen, and it will be costly, but I'm prepared for that. The rest of the work will be done in stages as budget permits. I see such great ideas in comments on Houzz, so I'm eager to see what suggestions others have for creating my dream home!