as much as alot of people think its all summery and warm in CA,it does get chilly at times, I live close to the Ocean and surprisingly in the summer is when it can really cool down,in N.Ca the coast really doesn't change temp much, its the interior that really gets cold in winter and hot in the summer.

in my shop/garage,what works for me is to use some carpet remnant and a old rug we have had for many years, for insulation and padding, and a space heater I use for when it gets really cold, it also helps to do some laundry when I am down there running the dryer serves dual purpose, warms the space and keeps the wife happy,2 young kids generates some dirty clothes