Hi people, I'm Kyle and I live in southern Victoria, Australia. I've been recently poking around the web doing some research in to making my own greenhouse.
So far, it seems that (In my local market cost and availability) twin film 6mil poly is the way to go with treated pine as the frame, but I have some questions that I found best would be answered by the experts.
So far the theory is:
Frame (And excuse the metric system, I'll try supply both when I can):
Seems like 50x100mm treated pine is the go (or maybe a bit smaller, 2x4" seems a little over kill, so I'll probably end up with 40x80mm (1.5x3") or something along those lines). Preferable size is around 2.4x2.4x2.4m (Roughly 8' cubed) - maybe a little wider depending on how I feel on the day.
Contents:
Mainly chillies, but I'd like some common vegetables in there as well (carrots, lettuce etc..)
Climate:
We're fairly cold down here in winter, sometimes gets to 0C (32F) some nights, average of around 14C (57F) during the day in winter. But also rather warm in the summer, half a dozen 40C+ days (100F) are not uncommon. As such, the GH will likely be a winter only GH, and I'll use my outdoor garden in the summer (Which does just fine).
Heating/Cooling:
Now I come from a technology background and I'm handy with micro-controllers (mini PC's), so I'll be implementing my own monitoring and watering system, which will also log temps, RH and CO2 levels. I'll be able to automatically water, vent and (electrically) heat the GH to my desire using automation - I've also got some questions on the desired levels of such I should aim for - but that will come after I've built it.
Insulation:
Now here's where I'm a bit stuck. 150 micron (6mil) PE film is pretty cheap here, and the plan is to have the frame built in a way as to have the long size of the wood as the walls (80mm) - then run the PE on the outside AND the inside of the GH so that there's a sealed 80mm air gap - which should also protect the inside from the treating process (chemicals) of the pine.
The floor is going to be dug up, sanded, salted and bricked/paved then painted black to absorb as much heat during the day.
My question is for the south facing wall (which will be about 150mm (6") from a fence). It will never get any sun on the exterior all year - and I was thinking of building a brick wall there instead of the wooden frame with PE - and painting it black to help with heat retention BUT I'm no bricky - and I don't want to have to pay for someone to put it in (and of course the foundation to support it) as it would probably double the cost of the whole thing.
Should I just go with just the PE on the south wall? Should I fill it with something, I.E gap filler? Polystyrene beads? What about reflective foil instead of PE?
What are your thoughts for this wall, to achieve maximum heat retention?
Any other pointers on my plans? What would you do differently?
Note that as the plan stands - to build this whole thing is probably < $350, and I'd like to keep it in the sub-$500 ballpark.
-Kyle.
keep all the walls a light color for reflected light that gives etter plant growth! With your warmer temperatures I would use water storage to maintain better temp control! I would put at least 4 50 gallon drums of stored water. If the greenhouse is easy to cover I would use a cheap plastic and replace it every year then you can use the greenhouse in the summer to grow some plants inside and keep into the dead of winter. I remove most of my greenhouse film before july here and grow climbing plants inside the greenhouse!