We live in San Jose California. Our house is 50 years old and I would like to add insulation to the outside of our stucco siding (concrete like material, about 3/4" thick). I was thinking about attaching large insulating panels (styrofoam or similar) similar to the ones they use all over Europe. I am looking for a pointer on where to start and find more information. Thanks,
Insulating the exterior walls of older homes has to be done carefully so you don’t trap moisture.
I would recommend you use some sort of mineral wool / rock wool insulation as they aren’t harmed by moisture and it will pass right through it. Walls need to be able to dry, so anytime you are adding to a wall its best to make sure that you only use products that are vapor permeable. Here is our page on Choosing the best rigid insulation,
you may also want to check out this page about choosing the right weather barrier
and How to install siding so walls can dry.