Hello @saturnzoon you can buy commercial foil off ebay, its sturdier than Alfoil and covers a wider square area. Bunnings may also sell it - thats another option.
You could get double sided sticky tape to hold it in place
or
adhesive squares with velcro on them.
With the velcro the sticky side would stuck on the window with the velcro facing up and the sticky side stuck on the foil also with the velcro facing up.
All you do is press both velcro sides together from the foil stuck onto the window and it should hold it in place.
I don't know what its called? Velcro tape?
So you can rip it off in winter and put it back up the following year without ripping the foil...
If you have awnings or blinds outside pull those down because once the heat hits the window it radiates through your entire house. Windows let in copious amounts of heat. So close curtains
I learned that from an environmental scientist who did an energy audit of my home and offered tips for pensioners - it was part of a community development initiative.
Another thing you can which the environmental sciebtist told me do is buy shade cloth that you see in parks. I think the shade cloth goes up to a 100% block out rating. You want a shade cloth with the highest percentage 80-100%. Its normally sold on a roll from Bunnings and you just cut it according to how much you need off the roll.
You use teeth to fasten the shade cloth to the top of the window frame and drape it like an awning and hold it in place with plastic clips on the bottom sides which you fasten with rope with tent pegs in the ground. The Bunnings website has it all. Its easy to do and its a cheap way to get awnings if your windows don't have them!
I checked out the Temu app, it was amazing. But the price range was pretty much the same.
