Spray Foam vs. Fiberglass: Two Insulations Duke it Out for Champ Status (Part 3)

If you were following along, we've been discussing spray foam and fiberglass insulation, specifically which one is better value for money. We've already mentioned that there's no clear-cut answer to that because the two types of insulation can't be compared, which we discussed briefly in our introduction.

In Round One, we discussed how fiberglass is a decent insulator, but doesn't do much to combat air leakage. As you know, eliminating air flow is crucial to a building’s overall energy efficiency and creating a high-quality building envelope. (If you need a refresher, you can read it here.)

That being said, let's move on to today's post.

ROUND TWO: Spray Foam as Insulator and Air Barrier

Air leakage may not sound like a big deal at first. What’s the harm in having a few cracks here or there, right? That might not sound like a catastrophe, but consider that the average building has more gaps and crevices than you might think: windows and doors are biggies, as are floors, walls and ceilings, but don’t forget about recessed lights, plumbing penetrations, fireplace flues, electrical outlets, vents and fans, attic hatches, wall air conditioners, mail slots…the list could go on and on. Adding all those areas up amounts to approximately 60% of the air in a building being lost through a leaky building envelope.

Spray foam to the rescue. Spray foam is two products in one. Because it’s spray applied, it fills every nook and cranny and hole and crack and crevice, thus eliminating air leakage. Partner this with a high R value, and you’ve got yourself a product that solves two major problems that exist in buildings today: insufficient insulation and air leakage.

Spray foam, in other words, is an insulator and air barrier. Now compare this to fiberglass that only insulates. Spray foam offers something that fiberglass can’t, an extra benefit that comes standard, like power windows in a car. Fiberglass will never be an effective air barrier, whereas spray foam by its very nature is an air barrier. Now do you see how these types of insulations can’t be compared? 

Stay tuned for our next post, when we answer the inevitable question (and the one we get the most): "How much more expensive is spray foam compared to fiberglass?"