These substitutes are bound to become an even stronger force once the current round of plant additions by fiberglass insulation producers has boosted capacity enough to meet demand(and then some).
Substitute products that deserve the most attention strategically are those that(a) are subject to trends improving their price-performance trade off with the industry's product, or(b) are produced by industries earning high profits. Substitutes of ten come rapidly into play if some development increases competition in their industries and causes price reduction or performance improvement.