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The basic measurement of concern here is the vapour resistance of a sheet of material. In SI units it's measured in GN·s/kg - giga newton seconds per kilogram. A typical value might be 20 GN·s/kg. That means that you have to push with a force of twenty billion newtons for one second to push a kilogram of water vapour through the sheet. Alternatively, you could push with one newton of force for 20e9 seconds (634 years and a month or so) or any combination which multiplies to the same amount.
An alternative way of writing this unit is as MN·s/g which is numerically the same but doesn't follow the SI convention of using base units in the divisor
Found that. Sounds like a lower number is more permeable.
frankenbike
@sacredhart
I'm looking at the vapour resistance of some building insulation products. These are measured in MNs/g. Is a higher number more or less vapour resistant?