Good ideas BorkBorkBork, I had new about underground living, even basements help some in the USA, but one thing you reminded me that what I did as a kid growing up was digging underground tunnels and playing in them. This is where my portable sand bag shovel would come in handy I bought years back. http://www.angelguardproducts.com/industrial/ezbagger/ezbagger.htm
I could either go underground or the double tarp idea would be a good start. When my AC went out awhile back I was going in and out of the lake all the time to stay cool, the house was 5 degrees hotter than outside with the windows open. The sun was brutal so I swam and hung out at the lake quite a bit till I got a new compressor. I should have stayed in the tent, it would have been cooler than the house. Anyway good ideas, thanks.