Which is better…Fiberglass or Spray Foam Insulation?

With all the decisions that need to be made during the initial stages of a project, not many put much thought into insulation.  However, doing a little research, can lead to major cost savings in the future.  There are 2 different kinds of insulation; traditional fiberglass and spray foam, each with benefits and drawbacks.

What is fiberglass insulation and spray insulation?

Fiberglass insulation

Slows down the transfer of heat by using very thin glass fibers that trap air bubbles.  These bubbles form an insulating effect by limiting the air exchange between areas and/or surfaces.  (Diffen)

Spray foam

“Developed from 2 types of composite materials.  When combined [during the installation process] these 2 materials chemically react to each other and cause their combined substance to expand and harden.”  (cleancrawls.com/why-spray-foam-insulation) 

• Open Cell Foam: the cells are broken and air fills the gaps inside the material, making it more dense and spongy to touch.
• Closed Cell Foam: the cells are filled with gas, so they are able to hold their shape, making them much stronger and a better insulator (Diffen)

What are the differences between fiberglass insulation and spray foam insulation?

Fiberglass	Spray Foam
Made up of billions of tiny glass fibers	Made up of a polymer (like polyurethane) and a foaming agent
Uses air bubbles to slow the transfer of heat	Acts as a barrier to stop airflow
Air leakage common (which can account for as much as 40% of AC costs)	No air leakage (when installed properly by experts)
Lower R-factor, so you need much thicker insulation	Higher R-factor, so less insulation required
Has the potential for mold growth and pest infestation	Kills mold and prevents future growth
Can sag and settle over time, requiring multiple installations	Will not sag or settle
Easy to update, re-install, or replace	Much more difficult to update, re-install, or replace
Less energy efficient	More energy efficient
Cheaper per square foot	2-3 times more expensive per square foot
High utility costs long term	Bigger savings on heating and cooling costs
Lucas Insulation  www.lucasinsulation.com/foam-vs-fiber-glass

As shown in the chart above spray foam clearly has quite a few more benefits than traditional fiberglass insulation, so it is up to you and your contactor to pick out the insulation that works best for you and your project.

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