Homasote
At Virginia Tech School of Architecture, back when computer drafting was still pretty much 2d (feeling older now), we used to build models a lot, by hand. We all got pretty good with an Olfa cutter. Chip board, foam core and Homasote were some of the products of choice. Homasote was rigid but soft, light, and a neutral grey which made for good backgrounds for more dramatic architectural statements. I have fond memories of the product. I recently attended a continuing education seminar and was reminded of Homasote as a building material. More so on a larger scale this time as a sound absorbing layer in wall and floor construction.
Homasote has done the testing so as to provide sound deadening assemblies to STC 60 for walls and STC 53 for floors. A great solution for projects where code or program require a sound absorption. With 98% Recycled content (newspaper) you cannot get much Greener.