Picked sprayed foam over fiberglass for my attic - here's what I found

I had to choose between spray foam insulation and fiberglass batts for my 1950s bungalow in Decatur. The spray foam cost me $2,800 for the whole attic. Fiberglass would have been around $900. I went with the spray foam because of air sealing. Three months later my AC bill dropped by $40 a month. The house stays way more even temp now too. Anyone else make this call and regret it or love it?

3 comments

3 Comments

simonk981d ago

yeah but hold on cuz i think you might be missing something here. spray foam is great for air sealing and lowering bills now, i get that. but in a 1950s house you gotta think about how that attic breathes. older houses are built to let moisture move through, and sealing it up tight with spray foam can trap humidity in the walls or roof deck. seen a few folks end up with rot or mold a couple years down the line because the foam stops any drying. plus if you ever need to rewire or fix something up there, fiberglass is way easier to move around. the $40 a month savings is real but that upfront cost difference is big too, and the long term risks can sneak up on you.

colescott1d ago

Seen a few folks end up with rot or mold" is fair but in my experience that usually comes down to bad install or not accounting for the existing vapor barrier, not the foam itself. I've sprayed a bunch of old houses and as long as you do the math on the dew point it works fine, fiberglass is a gamble with moisture too if there's any air leak.

simon_carr1d ago

Changing my mind on this after reading your breakdown. Always figured spray foam was the smarter play for old houses, but you make a solid point about moisture getting trapped in walls built for natural airflow. That rewiring thing scares me too, never thought about what a pain it'd be to dig foam out later.