If you have west facing windows, you know how they can heat up the whole house in the summer. Someone once told me this tip to help keep things cooler in the summer: Put a strip of tinfoil across the tops of each west facing window in your house. Put the shiny side out, and you can use almost any kind of tape to hold it there, or even thumb tacks. You will be surprised how much cooler it makes those rooms, and the rest of the house. I have been doing this ever since then. Take them down when the weather cools off in the fall. You may need to put some plants outdoors, but most people do that anyway.
Thanks for sharing this tip, AAnightowl, I'll definitely give this a try! (Not just yet, though, I just heard on the news that by the end of this week temps will be back to 11C. Heating on, wooly jumpers, hot soup. Again )
Our summers rarely get warm enough for me to try this out. If they do ever get too hot to handle though I have plenty of tinfoil in my kitchen cupboards. :-D