We are in a warmer area however put in undertile (inscreed) heating in the bathrooms. It is great. As it is not in the slab it does not take long to heat up and we have it on a thermostat which works well. It cost about $1000 for two bathrooms. A larger area would be cheaper as much of the cost was in the timer, thermostat and controls. We then did not bother with a tastic thing on the ceiling which is inefficient and just have a nice light fitting and a plain exhaust fan. I would see it as a must have. You might only have options for underfloor heating under a tiled floor with an existing slab. Have a think about slow combustion. They are dirty and dusty. The wood is a lot of work and can be expensive depending on your area. They may also take up a lot of space in your house and you need to have them close to a door to bring the wood in. They work for us at the moment as I am at home with young children. When I was at work it was an insufferable chore to get the fire going of an evening when I got home from work and there was washing to be brought in. I would see it as a "nice to have if you have the space, time and wood" Think about your lifestyle are you at home a lot or just after work? This will impact on what you need. I would go gas if I had access to it. Just make sure whatever system you have has zones and a programmable timer to reduce cost. Reinsulating your roof goes without saying and will make a big difference.

If you go for down lights you will need to leave a gap around them of 100 mm between the recessed part and insulation so the insulation doesn't catch on fire. This also creates a problem with the thermal performance of your home because heat can move freely through the ceiling where there is no insulation. It can make a big difference even if there are only a few down lights. Also, down lights are very directional (send most of their light straight down) so you need to put more in to get the same effect. You could try track lights that attach to the ceiling instead. If you want a pendant go for something cheap and easy to replace if it is damaged by toys/clothes or whatever being thrown around. Ikea have lots. FYI dimmers don;t educe the power consumption, merely reduce the intensity of the light.

Well it's is simple, as we will now have concrete floor that get huge amount of winter sunlight in that main living room area our thermal mass figure went up. with the use of phase change material in the roof it to give a thermal mass effect but lot less weight. What it does is stores the energy/heat and transfers it back into room a night. You must realise that this is a very exposed site and we had to get min 6 star rating. Our insulation goes like this from roof down 1, R7 Rock wool batts 2. 90mm Phase change Material 3. to support pcm you have to use 12mm ply sheeting in place of plasterboard 4. Float concrete 5. Electric in slab heating 6. Precast tilt, but played down slabs Underslab 7. R7 Rock wool again 8. 75mm foam batts 9. Reflective foil 10. Box in around steel and make air tight as possible Also all the glass is double glazed, argon filled and thermal shield. We had all that minus pcm and failed because standard way of accessing doesn't have it in calulations. i had to go and show council a sample of the stuff an how it works. This is not cheap but we can just about say that room will sit at a constant 21 to 24 degrees all year around without need for air conditioning . Phase change article

thank you for all of your comments. The main issue is that this wall faces quite a steep hill, so if I excavate too much I run the risk of creating a 'pool' under a suspended floor, facing the hill. This would be a disaster for the old double-brick home, which already has damp problems from water from the hill. My other concern about a slab is creating a permanent damp patch next to the house, assuming the black plastic membrane under a slab would be permanently damp (no evaporation). The mortar throughout the original house is lime mortar which is highly permeable and turns to dust when permanently damp John Cameron, I appreciate you mentioning passive solar, I'm familiar with this. Would it be best in this case to put rigid foam (say 50mm) under the actual slab before casting it? There will still be a thermal bridge at the perimeters though. MB Design I like the idea of a graded slope under a suspended timber floor, so will check with a structural engineer as to 150->400 allowance, noting my comment above about not wanting to pond water Two's Company I like the idea of a cement sheet for the wet room area - I have actually done a bathroom like this before and it works with great waterproofing. TBH I'm wondering right now if I should just redesign the whole thing. I'm going to make another post to canvas opinions on the two options and costs. Thank you! Sue