A better option in addition to the roxul is to first use spray foam in all of the headers of your basement this deals with air infiltration and thermal bridging.
Spray foam vs batt insulation basement.
Unlike spray foam insulation that acts on its own fiberglass batt insulation and poly plastic require one another for the system to be effective.
Spray foam insulation doesn t retain water so it also doesn t promote mold.
It s generally 3 to 4 times what you ll pay for blown cellulose or fiberglass.
It is made from fiberglass strands that create a barrier for air flow.
Thermal bridging means cold air conducted along the structure from the outside to inside.
Spray foam creates an air barrier that will seal up your basement to stop the outside air from getting in.
I d blow insulation on the attic floor after air sealing of course.
Insulating your basement with roxul or other rock wool batt is a good option this type of batt withstands moisture problems that result in sagging in fiberglass insulation.
For instance a 5 5 inch wall cavity can be filled with 2 inches of foam and an r 13 fiberglass batt as a cost effective system that seals the walls with an r 25 insulation system exceeding u s.
The big disadvantage with spray foam is cost.
Fiberglass insulation is significantly cheaper than spray foam insulation but it is also less effective especially in extremely cold conditions used in roughly 85 of american homes fiberglass insulation is the most common form of home insulation.
Spray foam insulation is designed to fill all of the nooks and crannies wherever it is applied including your basement.
Spray foam insulation has less market share but is increasing in popularity.
A poly plastic layer and sealing is needed to provide an air vapour barrier.
Batt insulation is that pink fiberglass found in exterior walls attic floors and the crawlspace ceiling.
If you don t have hvac and ducts in the attic spray foam on the roofline isn t really necessary.
Learn more about spray foam.
Spray foam can be used almost anywhere in the home including exterior walls ceilings floors attics and basements.