Fiberglass has been around since the Model “T” and continues to be widely used for one reason; it is very cheap. But insulation, like the model T, has technical leaps forward. A home insulated with fiberglass may seem like a bargain until you realize the monthly costs associated with maintaining the house. Just like with cars, the true cost of the house includes its monthly energy consumption to operate it. The problem with fiberglass is that it is a very poor at stopping airflow, so the heating and cooling you pay for just leaks out of tens of thousands of small gaps located in the entire heated and cooled envelope.
If you hold the idea that a house needs to “breathe”, would it not be far superior to design when, where and how much fresh air intake you want?
For the privilege of a few thousand dollars less in build cost, you get a home that will consume energy for the life of the structure at double the rate of a home that is spray foam insulated. In fact when the energy cost and monthly mortgage payment are added together (the true cost of ownership) the foam version is lower from day one and will continue to save you dollars for life. It’s like having the option of a car that gets 25 mpg for 25,000.00 or a car that gets 50 mpg for 30,000.00.