|Extremegreen||Cement Board||Gypsum Wallboard||Gypsum Sheathing||Plywood||OSB|
|Flame Spread||0||0||Low / 15||Low / 10||High||High|
|Combustibility||Non-combustible||Non-combustible||Paper Facing||Paper Facing||Highly Flammable||Highly Flammable|
|Water Resistant||Yes *||No||No||No||No||No|
|Impact Strength||Very High||Medium||Low||Low||High||Medium|
|Carbon Footprint||Very low||High **||High **||High **||Low ***||Moderate|
* Whether magnesium oxide board is actually water resistant or not is entirely formula and manufacturer dependent. Most magnesium oxide manufactured materials are not water resistant despite the manufacturers’ claims to the contrary.
** Cement board and gypsum board manufacturers may/do claim that their manufacturing operation(s) have a low to moderate carbon footprint, however, this is only achievable if significant quantities of fly ash are recycled and used as fillers in their board(s). Fly ash is usually toxic, or contains some degree of toxicity. The presence of fly ash in any building material cannot be advantageous to human health. In conclusion an increase in fly ash in turn increases the negative health effects to people.
*** Plywood and O.S.B. manufacturers should only claim to have a low – moderate carbon footprint if the wood used to manufacture their product(s) is harvested from a sustainable re-forestation programme. Even so, it remains debatable that replacing a naturally slow growing tree with a fast growing softwood tree is an ecologically sound practice.