Understanding floor protection requirements for Jotul #8 (circa 1980's)

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New Member
Jan 22, 2019
Ithaca, NY
TL;DR: What does this mean?
2 layers of 3/8" millboard where K=0.84 BTU IN/FT² H °F required.

Does this mean that this k value is required? First of all, I can't find a straight answer for how to convert a k value with these units into an R value. Second, by saying "where required", is it saying that it's not required unless you're in a location where local regulations require it?

Long story:
Hi! We're finishing a converted garage. Right now the woodstove, a Jotul #8, circa late 1980's, is on a hearth of loose bricks over a subfloor, which is not up to par. As we finish and floor the room, our plan is to move the stove, continuously floor with vinyl plank flooring, then rebuild a hearth on top of the flooring and replace the stove.

I thought we had it all figured out– we have a beautiful piece of vermont purple slate that's well beyond the size requirements of the stove as specified in the manual, but I can't figure out if the stove requires just floor protection for ashes / embers, or if there is an r-value requirement for the hearth pad as well. My understanding is that slate's r-value is fairly low, about .1 / inch of thickness according to https://chimneysweeponline.com/horvalue.htm.

I've attached a screenshot of the stove manual's chart showing the floor protection requirements. Any help appreciated– is our plan for using the slate adequate, or do we need to add a layer of high-R-value material underneath? If so, what total R value is required?
Understanding floor protection requirements for Jotul #8 (circa 1980's)