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Passive solar house build

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On 28/09/2017 at 7:50 AM, 125dBmonster said:

Thanks Rob

For those who see the power system as  total overkill (it is), it's because the Dweller is the manager of a Solar Electrical Business and has been collecting gear for 2 decades for this job

/& you'll definitely need a Topaz or Elgar 2.5-5kVa iso transformer, 0.0005pfd, between power & audio stuff ...

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12 hours ago, jamesg11 said:

/& you'll definitely need a Topaz or Elgar 2.5-5kVa iso transformer, 0.0005pfd, between power & audio stuff ...

Yep, on it. That's why there are 2 phases (2 power inverters) They weigh 60Kg each with a 5Kva TX in each. There is another Toroidy Supreme 400va Isolation Transformer for the front end of the single ended system as well. Fairly well sorted for power supply.

EOD it's all about the battery as well 

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Posted (edited)

Good to see that there are a few people here who share my own concern for living sustainably.


A few things that I think might be useful. Firstly, I need to say that I am in Canberra, 600m above sea level and 200km from the sea. We have very cold winters and hot summer days with cool nights. Summer has almost still air. Spring and Autumn have the most wind. Days are generally sunny and cloudless with very few full cloud and rainy days. Rainfall comes in short bursts during Spring and Summer.


I bought a north facing passive solar designed house from a friend 12 years ago. It was built in 1984 when most builders and designers knew little about energy efficiency. I have spent the last 8 years making improvements. Here is what I learned and did.


The biggest problem with the build was that the house was designed for cross flow ventilation and had large sliding doors in the North side and many opening windows on the south side. For some reason the bedrooms located on the Western side had narrow windows on the west wall. A pergola with grapevines and wisteria was on the north side and no eaves there. There were eaves on the South side and none on the east or west. The west wall was bare and double brick. The rest is brick veneer and dark coloured.


To correct these problems, I first attached trellising to the west wall and planted Virginia creeper on it which grew rapidly to cover the wall with its own inbuilt 50mm air gap between leaves and the wall. The first Summer I lived here temperatures in the rooms on the west wall were over 32 degrees at sunset. Now they are rarely over 28 degrees on a 40 degree day.


The next thing I did was to replace the sliding doors. They were built from cedar and single glazed. The timber had warped leaving a gap of up to 15 mm between the fixed frame and the door. This let insects and hot or cold air through. Also the sealing around the windows and door frames was not very good. Any breeze could be felt - leaving unsealed gaps was standard practice in building then, I understand. Replacing the sliding doors with a fixed double glazed window and a new uPVC double glazed French door meant that I was able to seal the gaps and air leakage reduced to almost nothing there. I did a similar thing with other windows - retrofit double glazing and sealing. I replaced two other opening windows that leaked air with fixed ones on the south and west. The other opening windows I had new frames made for the opening part and a built in seal to stop air leaks. Overall this (slightly expensive) work has produced the greatest benefit.


Next challenge was to do something about the heating. Heating was from a wood heater. I had a very large pile of wood from a giant tree that had to be removed because it was overhanging powerlines. That wood lasted 5 years. However, wood heating is good when you have a wood supply and someone around during the day to keep it going. You do have to be tolerant of dust and very dedicated. However, my lifestyle changes once my son went to university and then to live overseas. I took on jobs that require longer hours and travel. This does not work well with a wood heater. The house was designed to isolate the large room where the wood heater was located and this meant a lot of doors and therefore dead spaces. Add to this that any decent artwork or (heaven forbid) sensitive audio equipment, including records were not going to survive. The photograph shows what I did once I removed the wood heater. The heater was right where the equipment is sitting in the middle of the wall. Essentially, I got back a quarter of the room by making this change.


- Removing the wood heater and making some space for some audio equipment.


After the first summer of over 30 degree evenings, I installed a medium sized reverse cycle airconditioner. It worked ok to moderate the summer temperatures and heat the house to remove the chill when I could not keep a fire going. However, the summer heat was a problem. With cool nights getting down to 15 degrees or even less it should be possible to cool the house by ventilation. Without a sea breeze this did not happen by itself. I installed an opening "roof window" that I control via  a remote. I open it in the evening and, because it is at 3 metres there is a convection airflow from windows though the open skylight. Venetian blinds and triple glazing on the glass keeps the sun out in summer and lets it in when I want it at other times. This bit of work means that I rarely use any cooling in summer - only when there are extreme days and hotter than average nights. Maybe 5-10 days a year.

Adding a screen/security door helped in Summer too. It improved circulation of air through the "solar vent" created by the skylight. Drawing large volumes of cool air over a slate floor means that the floor gets close to the lowest morning temperature wherever the breeze moves. A good thing.



Old sliding door being removed



New Glass double glazed unit


New uPVC french door. total seal and very secure window. Also using Starfire glass


A note on the double glazing. In Canberra the key to double glazing is to take into account our cold sunny winters and hot dry sunny summers. On the South side the ideal glass is a low-e type that provides a good thermal barrier. No sunlight gets through in Winter so the lower transparency of the low-e type (around 70-74% transmission) is therefore not an issue. On the North side it is a different story. I want the most sunlight in during the Winter and using a type of glass called StarFire gives me a bit less than 92% transparency with the dual layers of glass. Overall this is around 20% more warmth let through. The glass is more expensive but worth it over a lifetime of maybe 30+ years. Payback period was 5 years. Of course the dollars are part of the story. The comfort of having a warm floor to walk on in the middle of winter - even early in the morning - is priceless. In late June and early July the sun penetrates to nearly 4 metres inside the house. The days may be shorter but the warmth on a sunny day is amazing. I frequently have 23+ degrees inside at 6 PM in the winter. Actual slab temperature (dark slate is 24 degrees when the air temperature is a little lower in July. I measured this with an electronic thermometer after dark about 6 PM. Outside temperature was 8 degrees on stone pavers at the same time.

To further improve the thermal efficiency of such large areas of glass, I installed Duette honeycomb blinds inside to provide a screen from outside and also noticeably reduce the feeling of cold from the windows. Be careful choosing installers. Most will not fit them flush with an architrave and leave gaps for cold/warm air to circulate - almost defeating the purpose. Specify before ordering.


Duette blinds adding to the insulation Summer and Winter



What to do about the pergola? Wisteria was breaking the structure and 35 years of weathering meant it needed to be removed or replaced. Given that the pergola had to go and that there is a problem with a fixed shading system like a pergola - fixed shading shades symetrically when you need less shade in September and early October and more in March and early April. Therefore I replaced the pergola with some retractable awnings that I can adjust to provide heavy shade out to 2 metres past the windows in Summer and retract them whenever I choose. They are relatively expensive but work far better. I will post some photographs. In the works is another little experiment. A "solar pergola" that will be half a metre wide and at 11 degrees angle covered in solar panels. Solar panels are hail proof and provide good shelter like proper eaves but are actually no more expensive than traditional roofing materials. Then they also generate electricity. All I need is to get a tradesperson to build the frame for me - It might not be before January now.



The old Pergola


No pergola but replaced with a retractable awming.


Hot water

I wanted to have solar tube hot water for the simple reason that it is so nice to have the sun heat the water for me. I arranged installation with a reputable supplier and specified two unusual things. First that the tubes be angled at 50 degrees and secondly that the "booster" be the existing instantaneous gas heater that I could turn off and on via the inside controller. To help with that, I also wanted an indoor display showing the tank water temperature.

Why monuted at 45 degrees? It is to maximise winter sun and minimise summer sun. The opposite of what you do for solar panels. Summer sunshine usually boils water heated by the tubes when there are many hours of sunshine at a high angle and fails to heat the water enough when there are fewer hours of sunshine and a low angle. The secret is to angle to collect the sun best a t the lowest angle and thsi means that the sun at a high angle hits a smaller target. The calculation of angle goes like this. Get your latitude. In my case about 34 degrees. The sun moves 23 degrees lower than this in Winter so raise the tubes to 34+23 =47 degrees. A couple of degrees makes little difference. At the equinoxes there is a reduced heat (ie hitting at an angle of 25 degrees) but more daylight which more than adequately compensates. In Summer it hits at an angle of 68 degrees and reduces the amount of boiling and venting of hot water in the tank. You really need to convince most installers that this is the right thing to do.


Solar hot water tubes at 45 degree angle


... that is all I have time for now. If anyone is interested, I can add some more to this post to cover water storage, micro climate, energy efficiency and solar/battery. Essentially, I am paid by ACTEW (gas, water and sewerage) after selling my spare electricity and using my own plus gas for cooking and heating in the depths of winter.





Finished interior with low power consumption audio equipment consuming about 50 W without the TV on and 80 W with it. Just the old Marantz Pre processor used 55 W.

Edited by Peta
Update and answering a question

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Thanks for this. Just spent a week in Canberra with friends - who need to do the sort of work you've done! Late 70's place, I think, down in the southern burbs. Brick veneer, slab, not N oriented, etc.

When I've stayed there in winter it's very cold. Classic bunch of windows with vent mesh at top etc; fear of the dreaded mould or florence nightingale syndrome, or something.

What temperature would that slab be by August? My thermal mass scepticism ...

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On 08/10/2017 at 11:04 AM, jamesg11 said:

What temperature would that slab be by August? My thermal mass scepticism ...

24 degrees typically in July. Sometimes 28 in August. September is around 25 because there is less penetration of the sunlight. Slab inside where no sun shines stays between 15 and 20 degrees. Several days of no sunshine means it cools down a lot.

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