The guide says that at least 75% of all insulation, by cost or surface area, meets the VOC emissions evaluation. Logically, if I decide to calculate my insulation by surface area, I must not consider the thickness. So hypothetically speaking, if I have a wall with three different insulation boards of 1" (total of 3") and I have an other wall with one insulation board of 3"... then does my second wall with 3" insulation only count for 25%?
Whereas by density/volume/performance, it would've counted for 50% and the other three panels for 16.666% each...
I just want to be sure I do my estimation right.