"We pay for insulation whether we have it or not" is an interesting quote from the Air Krete web site. I'd been hearing about this company and its insulation product for a little while, so I headed out for a look.
 
Air Krete is spray-in insulation, made from magnesium oxychloride cement, air & water. 

Magnesium oxychloride is created by adding a solution of magnesium chloride to magnesia. Magnesium chloride is used in food, de-icing and medical and veterinary applications. Magnesia is magnesium oxide; used in cement, as a desiccant and also in medical applications.

Magnesium is the eighth most abundant element in the Earth's crust and ninth in the known universe - thus spaketh Wikipedia.

According to the company, when used as a spray in foam, it expands, gets into all the nooks and crannies in your walls and above your ceilings and then hardens into cement coated air bubbles.

Air-Krete - Attic application

Air Krete has an R value of 3.9 at 2.07 lbs/ft3, is fire proof, non allergenic, mold resistant, pest resistant, regulates indoor air humidity and also acts as a sound barrier. An interesting feature mentioned by the company is it actually scrubs carbon dioxide from the atmosphere.
 
They say it is cost-effective, but as to an actual price, I don't know. However, the opening words of this post remind us that we sometimes need to spend a bit to save a lot and in this case it's not just money over the long term, but emissions related to heating and cooling our homes.
 
I've heard this stuff is far superior to blow- in cellulose in a number of ways. However, just from an environmental viewpoint, cellulose insulation is usually made from recycled materials, whereas magnesium must be mined and refined - both very energy intensive and not without other environmental issues; so its green street cred is a little iffy in that respect. I'm not sure if Air-Krete can be recycled or repurposed.
 
I haven't seen this product over here in Australia, so I'm curious about the experience Canada and USA folks have had with Air-Krete. 
 
If you have Air-Krete or a similar insulation product based on magnesium oxychloride cement installed in your home, what are your thoughts? If you don't mind sharing the approximate cost, I'm sure many others will be interested in that too.

Related:
 
Environmentally friendly roof insulation
Saving energy with blackout curtains
Air conditioning and staying cool indoors
Wood heaters and efficiency