Browse Forums Heating, Cooling & Insulation 1 May 28, 2014 9:58 am We're going to be building a 220sqm single level home on a slab near Canberra. The block is in an elevated position and house has a good rear-north aspect. I'm putting all the bedrooms on the east and garage/workshop/covered alfresco on the west. I'm trying to work out how to approach the heating/cooling and solar/electricity etc for this climate (we're not from the area). Essentially we're happy to invest in solar panels as we'd like to minimise our energy costs moving forward but there are so many systems out there that I don't really know where to start. Is there one that does everything? (heats/cools house, heats water, maybe filters air (due to allergies)?). TIA Re: Heating/Cooling and solar 101 - for Canberra region 2May 28, 2014 10:25 am I'd be looking at a 5kw solar electricity system. Plus a solar HW. Canberra has relatively cheap electricity and a good feedback tariff. As they have natural gas I'd probably go for that for heating and also use split cycle air con. I know it may cost a tad more - but the nat gas is wonderful for heating. And the reverse cycle is gr8 for cooling. I'd be wary of the evap cooling systems - as Canberra can get VERY hot. I mean nights where it stays hot too. check the deals on offer and check with ACTEWAGL - they often have deals where you get a loan - pay it back with your bills - over a good period - no interest. Re: Heating/Cooling and solar 101 - for Canberra region 3May 28, 2014 10:26 am Sorry - aspect is essential in Canberra. Try to utilise the north and make use of veranda's etc. Re: Heating/Cooling and solar 101 - for Canberra region 4May 28, 2014 11:23 am Yes all the living spaces will open to the North and be protected by eaves etc. Do people in the area normally heat the slab? I was wondering if a slab heated (via solar during the day) would result in a warm house all winter. And then just run aircon in the summer? Re: Heating/Cooling and solar 101 - for Canberra region 5May 28, 2014 11:42 am bung Yes all the living spaces will open to the North and be protected by eaves etc. Do people in the area normally heat the slab? I was wondering if a slab heated (via solar during the day) would result in a warm house all winter. And then just run aircon in the summer? Solar slab heating might be good - but you can get days in Canberra where the temp doesn't get above 10. Using E to assist might be costly. Nat Gas is relatively cheap. I knew someone who had a heat bank - a wall of bricks that would absorb the sun. It was nice - but never rally warmed the house. Don't really know enough about heating the slab with solar to advise - sorry. It might work - but might mean cool mornings ... Canberra can have many sub-zero nights - bird baths freeze, lawns go white and crackle under foot etc. But the days can be glorious. Re: Heating/Cooling and solar 101 - for Canberra region 6May 28, 2014 4:40 pm bung We're going to be building a 220sqm single level home on a slab near Canberra. The block is in an elevated position and house has a good rear-north aspect. I'm putting all the bedrooms on the east and garage/workshop/covered alfresco on the west. I'm trying to work out how to approach the heating/cooling and solar/electricity etc for this climate (we're not from the area). Essentially we're happy to invest in solar panels as we'd like to minimise our energy costs moving forward but there are so many systems out there that I don't really know where to start. Is there one that does everything? (heats/cools house, heats water, maybe filters air (due to allergies)?). TIA Hmmm, where to start? Sounds like you've got the layout sorted with good passive solar design. Canberra has a high diurnal range (of around 13C), that's the variation between daytime maximums & night-time minimums. So along with a well sealed highly insulated house with correct orientation, you want to build a house incorporating high thermal mass materials in the interior (concrete, masonary, water), which will smooth out those daily high & nightly low temperatures. So I'd suggest leaving your slab exposed (polished or tiled) in the northern living areas. In winter the slab will soak up sunshine & release the heat once the sun goes down. In summer, try to allow cool night-time breezes to flow over the floor. This will keep your house cooler in the day. If you cover the slab with timber or carpet (both insulating materials), you will limit the benifits of the thermal mass. Make sure your northern eaves are the appropriate size, large enough for complete summer shading, but small enough to allow plenty of winter sunshine to penetrate (a northern veranda is not recommended, though other aspects are great). If you struggle with allergies I'd try to stay clear of forced air heating & cooling, with all that dust being blown about. A bit of a pity, as some reversed cycle systems are quite efficient. Radiant heating will be much more pleasant for allergy sufferers. For radiant, an hydronic system (using hot water), will have much, much lower running costs than an electric radiant system (cost prohibitive for the whole house). But be aware that the up front costs to purchase an hydronic system can be very expensive. If you go down the hydronic route you have a few options. Underfloor, as you mentioned, wall panels, base board (skirting board), or trench heaters. You also have a few options, when considering how to heat the water for an hydronic system. Gas, as mentioned, is relatively cheap to run. However the price is increasing pretty rapidly. Also it's not great for the environment. As the heat input required to heat a house are much higher than the heat required for domestic hot water, solar hot water hydronic is not recommended. Solar struggles to heat a 300 litre domestic water system in winter, so would require endless boosting for an hydronic system. My preferred option would be a heat pump hydronic system. Heat pumps run on the same principal as a reverse cycle air conditioner (which is actually an air-sourced heat pump). These are very efficient, between 2 & 5 times more efficient than electric heating. Their efficiencies drop off in colder temperatures, so I'd run the heat pump in the middle of the day to heat your storage tank (powered by your solar PV). I believe you can get heat pumps that will heat both your hydronic system & your domestic hot water system. As for cooling, as mentioned, passive cooling with high thermal mass & good cross-ventilation will work well on cooler nights. But for hot, still nights you'll need more. I actually believe that evaporative cooling would work very well for Canberra, as it's a dry heat. Evaporative cooling works well in dry environments, but performs poorly in high humidity climates. It is much cheaper to run than air conditioning, but requires some water to run. As mentioned, the whirlpool green tech & energymatters forums are great resources. Another is The Alternative Technology Association, http://www.ata.org.au/forums/ . Lots of very knowledgeable peope there. Re: Heating/Cooling and solar 101 - for Canberra region 7May 28, 2014 6:49 pm Can I ask - have you - or do you - live in Canberra ? Or is what you said theory ? Anyone who lives there - or who has lived there - knows that although they claim to have a max of maybe 18 - 20 in winter sunny days - that max lasts about 45 minutes - then starts to fall. Unlike - say - Qld. You are right evap cooling does cost less in general terms - but this must be weighed against what you want. Do you want to reduce the temp to 25 degrees when you want it - or do you want to sweat it out on those long hot summer nights. Re: Heating/Cooling and solar 101 - for Canberra region 8May 29, 2014 4:16 am No I don't live in Canberra. I live on the beaches of Sydney, a very different climate to Canberra. So I guess you can call it theory. Not just my theory though, the Aussie government tends to agree
http://www.yourhome.gov.au/passive-desi ... gn-climate . Canberra is Zone 7 - cool temperate. Passive solar design works well in many climates, not just warm climates but in plenty of cooler climates too. As long as the heat gained from the sun shining through your windows exceeds the heat lost through this glazing you're ahead. So in cooler climates care must be taken not too overglaze, & highly insulated double glazing is essential (along with insulating blinds or curtains). Where I live I wouldn't dream of having a high thermal mass build, or use evaporative cooling, due to the high humidity & low diurnal temperature range. I have however spent plenty of time in Tamworth, which like Canberra has very hot dry summers, with a high diurnal range. I remember my granddad had an evaporative air conditioner, & thought it was very effective. Over the years it has been replaced by a ducted refrigerated system. Solar panels have recently been installed to offset the very large electricity bills. All systems will have pros & cons. An evaporative cooler will be much cheaper to buy, much cheaper to run & should require less maintenance. It will work well in dry conditions, but will be less effective on higher humidity days. It raises the interior humidity, & requires water to run (up to 25l per hour for a large system running at capacity in a dry climate). It refreshes the air & requires airflow, so some windows must be opened a small degree. A refrigerated system will be more expensive to buy, much more expensive to run, & is likely to be more expensive to maintain. It will be very effective in all climatic conditions, & will be far superior in hot humid conditions. It will however recycle the air, drying out the interior environment. Nothing's perfect, pluses & minuses for most things in life. Re: Heating/Cooling and solar 101 - for Canberra region 9May 29, 2014 11:15 am Agree on some of that. I might add as a downside to reverse air con - they can freeze up in mid winter. They de-freeze (is that a word) quickly - but it can/does happen. I have friends there with evap cooling. It works well a lot of the time - but on the really hot days (and there are quite a few of them - and nights) it can't handle the temps. It reduces the temp - but nothing like an air con. But agree - can be much cheaper. It all depends on what you want - and what you will pay ... Re: Heating/Cooling and solar 101 - for Canberra region 10May 29, 2014 11:50 am Yeah, you're right. The reverse cycle will perform better on those extreme days & nights, but at a cost. All up to personal preference, & what you're willing to sacrifice. $‘s or some comfort on those extreme days. This is one time when a tight, highly insulated, high thermal mass build will work well with the cooling system. The thermal lag from the thermal mass will minimise the interior temperature rise throughout the day. Night purging, plus the cooling effect of the cooling system will reduce the temperature of the thermal mass. The cycle is repeated each day. The only time this will fall down is over multiple days of extreme conditions with very hot nights. Here, the temperature of the thermal mass will gradually increase, making it less effective. Note, the thermal mass must be inside the building envelope, protected from the exterior conditions. This is one reason I really don't like brick builds, particularly on the upper storeys. Heats up & takes forever to cool down. Yeah, icing up can be a problem for heat pumps when heating in extremely cold conditions. Here the running costs can increase substantially, as the electric booster runs to de-ice the system, along with the general reduction in efficiency at lower temperature. In these conditions a heat pump that uses CO2 as it's refrigerant will perform much better. More efficient than other systems at these temperatures, & doesn't require de-icing. Re: Heating/Cooling and solar 101 - for Canberra region 11May 30, 2014 6:51 pm I lived in Canberra. Heat pumps do not work in sub-zero conditions, I.E. in winter nights in Canberra. My heat pump continually iced up in winter. When this happened the indoor fan coil unit shut down, went into defrost cycle & I froze, So I went to the local pub (heated) where it was cheaper to sit on a couple drinks all night than use electric heaters in my apartment. Friends who has ducted gas heating were toasty warm. My recommendation is to go down the ducted gas heating path I Canberra ( or resign yourself to sitting in the local bar every night throughout winter) Re: Heating/Cooling and solar 101 - for Canberra region 12May 30, 2014 7:36 pm CO2 heat pumps (such as Siddons & Sanden) are said to perform much, much better than other heat pumps. I believe they don't ice up, & have COP's (efficiencies) which are much higher than other heat pumps. This is particularly true at colder temperatures (although their COP's still drop off substantially). They are expensive though. I'd recommend heating water with a heat pump in the middle of the day, when the air temperature is higher, particularly if you have solar PV to power it. Keen to hear from people in the area who have got KDRB done on whom they got the build from? Looking for recommendations. 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