I plan on reinsulating my attic. I will be taking all the old fiber glass insulation out and replacing it with Roxul. I will put a layer of R30 then a layer of R15 on top of that. When all the old insulation is out I plan on cleaning the attic because of mice and things of that nature. Is there a sealant, disinfectant, or protection I should use before reinsulating? Also, should I just put the R15 on top of the R30 or should there be something in between the layers?