Its role is growing in improving the quality of life inside older homes as well. Foam insulation is generally a polyurethane product, and much of it is sprayed on surfaces or injected into walls.

The book distributed by 475 recommends insulating thick brick walls on the interior with cellulose or fiberglass insulation — a controversial method.

Cracked and peeling walls at Lushan County Junior Secondary School exposed bricks that were either hollow or filled with “polystyrene foam”, party mouthpiece People’s Daily reported on Thursday.