Monday, January 4, 2016


The theme of this blog post is evacuation.

As I mentioned in the last post, it's summer and it's hot. Some nights, we get a cool change, but the breeze is very light. In winter, I built a rooftop solar collector and pumped solar heated air into three rooms using ducting. This system worked quite well, but it would have been better if the indoor vents were not in the ceiling but were instead in the floor. There is an advantage to having them in the ceiling though, and that's when we want to pump hot air out of the house. To do this, all I've done is change the configuration of the thermostat: previously, it switched on when the temperature was above 24 C, now it switches off when it is below 26 C (this is measured at the solar collector, which is at about 80-degrees from horizontal so still gets some sun) so it basically won't switch on during the day.

I've also reversed the fan (I bought an AC fan which only works in one direction -- others may want to consider a DC fan which is reversible with a switch), and opened the (in-duct) backflow preventer with a bulldog clip (the backflow preventer stops warm air from flowing out of the house during winter). This works really well for sucking hot air out of the house in summer -- probably better than the system works as a winter heater. It really lets us capitalise on cooler nights which, with a double brick house, means keeping things cooler during heat waves very cheaply. The fan uses about 50 W, so to run it overnight (when our solar PV isn't producing) uses .05 * 8 = 0.4 kWh. To improve it, I will add better control so I can easily turn it on and off from within the house.

On to a different type of evacuation, I've ordered a urine diverter so that I can build a composting toilet (that was my Christmas present for myself). I went for the we-pee, which costs AU$66 delivered (I don't have it yet). That seems a fair bit of money for a little bit of plastic, but I thought it was worth doing this properly. My plan is to build a bucket-based composting loo using 20 L plastic buckets, and just add in hay/mulch/etc as we go. It's all a bit experimental, but I'll write about it as it goes and let you know.


  1. Hi Angus,

    Top work with reversing the solar heater to be some sort of a solar tower drawing hot air out of the house. Nice idea. DC fans are really cheap and quite powerful as 12V and 24V ones are available used in car and truck thermo radiator coolers.

    It will be very interesting to see how your composting toilet goes. It is a great use for all of your manure and the garden will get heat and drought hardier with every bucket. I put down another cubic metre of manure today in the orchard and the fruit trees love that stuff. I've seen saw dust used in composting toilets and that seems to work well too. There is very little smell other than a sort of earthy smell.



  2. Hi Chris,

    I remember you recommending a DC one earlier (which would have been great) -- unfortunately I'd already ordered one. It would have been much cheaper to follow my usual policy of going second hand...

    Definitely true about the lack of smell. I've used a bucket composting loo quite a bit which, though very uncomfortable without a seat, doesn't smell when there's plenty of carbon rich matter.

    btw -- your post about the sprinkler has inspired me to finish setting up drippers on all the fruit trees. I spend too much time watering!

    Cheers, Angus

  3. Hi, Angus!

    I like your ideas presented here! Clever thinking. Will be interested to hear more about your composting loo. Also, found your comment at ADR today very concise and thoughtful.


  4. Thanks Pam, glad you're enjoying the posts.

    Best wishes, Angus


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