Spun glass fibers made just like cotton candy only at 2000 degrees.


  • Essentially non-combustible.
  • Non-corrosive.
  • Fairly inexpensive.
  • Sold everywhere. 30-40% recycled, the rest is sand which is a rapidly renewable resource.
  • Decent R-value/inch.
  • Does not absorb moisture.
  • Will not support mold/fungus.


  • Itchy.
  • Can perform very poorly if air can blow through it, which happens in attics and often inside walls that are poorly sealed.
  • Loses substantial R-value as temperature falls, approximately 20% at 30 degrees and 50% at -20 degrees. Slightly more expensive than cellulose.
  • Diminished R-value due to thermal bridging.
  • Does not prevent radiant heat transfer – the primary source of heat-flow in and out of buildings.
  • Pinching, smashing and thermal bridging reduces its R-value.
  • Moisture reduces its R-value.
  • Potential health risks such as lung damage.
  • Batts do not seal wall and ceiling cavities tightly.
  • Needs an additional vapor barrier to protect it from moisture.
  • Can settle resulting in declined effectiveness.
  • Moisture build-up between the fiberglass and the building exterior cannot evaporate, therefore causing mold, mildew and decay.


Radiant Barrier
Rock Wool
Air Krete
Open Cell Foam
Closed Cell Foam