The best insulating product for homes and business buildings is spray foam insulation. Spray foam reduces heat transfer much better than fiberglass, saves more money on utility bills, and also completely seals out all leaks from gaps in building materials. While spray insulation is the superior insulating product, fiberglass is cheaper and can be a do-it-yourself project. Spray foam requires trained technicians and a professional installation to achieve the best outcome and to minimize installation time.
Another disadvantage of fiberglass insulation is the fact that it eventually will need replacing. Over time, fiberglass loses its insulating value, or R-value. Starting out with an R-value of around 2.0, losing a bit of that value year after year means that 10 to 20 years down the road, the fiberglass batts will need to be removed and replaced. This will be sooner if the fiberglass insulation gets wet. Spray foam holds its 3.0-6.5 R-value throughout the lifetime of the product and should never need replacing. That’s why manufacturers offer limited lifetime warranties on the product.
Because spray foam insulation is a one-product-fits-all solution, it is also superior to fiberglass in that it performs many functions at once. First it insulates. It also seals, is an air and vapor barrier. In the case of closed cell foam, it is also a structural strengthener. To perform all these duties, fiberglass would need to be augmented by a vapor barrier and be fully sealed which is a separate process, too. While fiberglass might be cheaper if you compare two bids for the same project, you will get much more for your money when you choose spray foam because of all the other services you don’t have to buy such as putting a vapor barrier down and sealing up cracks and crevices first before batt insulation is installed.
If you are looking for a way to sound insulate your movie room, then spray foam should be your top choice. Open cell spray foam is a terrific sound insulator compared to fiberglass. Outside noises such as auto or air traffic can be significantly lessened by the use of spray foam on walls and in the attic.
Finally, fiberglass adds zero strength to building structures. When you use closed cell foam, as is recommended in high wind areas or where there are hurricanes, the walls and roof members are reinforced with the dense structure of closed cell spray foam. This is something that fiberglass insulation can never do.