Backyard Aquaponics
A place to discuss aquaponics

for this one, just doing single skin poly tunnel. Can you explain further the double skin with fan. I've never heard of that.

oh yeah, and will double skin let in enough heat in the winter (it will be in 85% shade in summer so hopefully won't overheat)

monya is that 85% shade as in shade cloth, or natural shade?

Basically just picture two poly skins layed over each other and then rolled a little at the ends before its screwed into a length of timber (this forms an air tight seal). a shoebox size hole is cut in the inner skin and a piece of thin wood (like that wood paneling you can buy for interior walls) is stuck over the hole. The small fan is then screwed to this panel and inflates the area between the two skins.

A friend that has a tree farm has all his poly tunnels sut up this way

Any more Q's just ask

natural shade Steve, under a massive deciduous tree.
That sounds perfect, you still only need one frame yeah? The poly is so cheap, only 10 bucks a metre for 7.5mtrs wide, would be fine to do a double layer. Seems like my plans may just have been modified

Is that tree going to give it too much shade during the summer?

I don't think the doube film will be an issue for the winter.

Yeh, same frame as far as i am aware

The double film acts as double glazing does. Helps cool in Summer and keep heat trapped in Winter.

when i was thinking about buying a kit, the bloke said I would have to have shadecloth over it in summer as it turns into an oven, so I figure I can put it under the trees. Will get some sunlight, also can thin the trees out a tad if required. I think (hope) the spot will be ideal, but if it is no good, I can move it to a different spot, which doesn't get as goo winter sun, but cops full sun in summer which I could cover with shade cloth in summer. This is going to hopefully be the location for system number 2 with a 7 metre long 1 metre deep 1 metre wide pond feeding four 2000 litre grow beds on a continuous flow system. WAll in a greenhouse of some description. Just trying to work out the logistics of such a massive hole in the ground ie lining it etc.... That's next years project, gotta get this one happening fitrst,

deciduis sp. is good i guess, as it self thins in winter

Yes. I was just sitting under my large tree marvelling at that very fact the other day. Beautiful shade in Summer and sun in the Winter.

You have a hotter climate than me. I may need shade cloth, cheaper than fans if it cools ok.

I'm putting on one skin first before hopeful Spring start. Contemplating reflective walls and whether to actually pink batts and timber the back for insulation with mylar roofing paper to reflect (white side very reflective - and FREE!)

I will skin entire outside and see how cashflow goes. I can transfer outer skin to internal walls easily should I decide on that route, outer skin is slightly larger.

your project sounds great!

reckon I'll do the same. I am pretty hooked and am spending more money than I wanted to, so one skin will have to do for a starters, then add the second one if it looks neccessary. The idea with the little fan is gold, I love it.

Yeah deciduous trees rule. In summer 80% of our backyard is under dappled shade, great for fish barbies (dreaming....)

WOW, ALL THIS CONSTRUCTION GOING ON!
Me, I just use a small stand of black bean trees to house my system, as well as act as my nursery/shadehouse... The leaves from the trees make great food for my worms.

oops, forgot, when will we see pics of these various systems?

I visited Dr. Savidov in Alberta, Canada (real cold winters) and they had the double layer with air blown in between. Air insulation depends on still air (at leaast I always thought so). This is blowing air around between the layers??? Also, what temperature is the air being blown in? Outside temp air is cold. Inside warm air would create a vacuum and pull in cold air from outside (like a fireplace without an outside air source does). People tell me this works, but you can see, I do not understand how. But two layers would certainly be better than one. But I would suspect the "R Value" would be pretty low.

Doug, the system i have seen with air being blown in-between a double layer does NOT vent the air out, just keeps it pressurised and accomodates slight leaks, pretty much how the jumping castles for kids work. Hope this helps clarify it for you.

Steve, that totally clears it up for me. The area between layers are inflated like a balloon. Then it is static if the space is not too wide. Makes sense that way. How the heck do they seal the two layers together?