DahlisMarie,
You may not have heard of Polytunnels because their main function is to keep the plants inside warmer than the outside. I our British summer this can be above 45 degrees Celcius with doors open at both ends, in which case the plants are certainly TOO hot. I dread to think what temps you'd get in Aussie
They are a God send to us as we can grow things later in the Autumn and earlier in the Spring than otherwise, and start off those tender plants two or three months earlier than if we were growing them outside.
I don't suffer from insanity .... I enjoy it!
Vivianne