Yeah, use silicon to seal them. They do not come sealed when you buy them. I didn't seal mine when I put them in. A lot of people don't. I saw a little fogging the first 2 or 3 days, and havent seen any since. (been over a month) But if you just don't want to take any risk of having to take them back off later to seal them because it keeps fogging up, then just pop them open and seal them before installing them.