I get what you're saying about needing airflow, but honestly, sometimes tighter insulation can still work great if you pair it with proper attic ventilation. Had a client who was convinced their insulation was the issue, turns out their vents were blocked by birds' nests...who knew?
Interesting point about ventilation, but do you think insulation type matters just as much? I mean, even with good airflow, wouldn't certain materials trap moisture more easily than others? Had a buddy who switched from fiberglass to spray foam and swears it made a huge difference in humidity levels...but maybe that was just his imagination. Could insulation choice be as important as ventilation itself?
"Had a buddy who switched from fiberglass to spray foam and swears it made a huge difference in humidity levels...but maybe that was just his imagination."
Nah, your buddy's probably onto something there. Spray foam insulation can definitely make a noticeable difference—it's not just his imagination playing tricks. Fiberglass is decent, sure, but it doesn't seal up gaps and cracks nearly as well as spray foam does. Those tiny gaps are sneaky little moisture highways, letting humidity creep in and hang around like an unwanted houseguest.
Ventilation is key, no doubt, but insulation choice is like the other half of the puzzle. Think of it this way: good airflow helps moisture escape, but if your insulation is trapping moisture or letting it seep in, you're basically fighting yourself. I've seen a few attic jobs where switching insulation types made a night-and-day difference in humidity and even mold issues.
So yeah, I'd say insulation choice is just as important as ventilation. Your buddy's not crazy—well, at least not about this. 😉
I get the logic behind spray foam sealing things up tighter, but I'm still a bit skeptical about how dramatic the humidity difference really is. I've inspected plenty of homes with fiberglass insulation that had perfectly acceptable humidity levels—assuming proper ventilation was in place. On the flip side, I've also seen spray foam jobs where homeowners still struggled with moisture issues because they overlooked airflow.
A few years back, I inspected a house where the owner switched to spray foam expecting miracles, but he didn't address the attic ventilation at all. Sure enough, humidity was still a problem. Once he finally added proper venting, things improved significantly. So, while spray foam can definitely help, it's not a magic bullet. I'd say it's more about getting the balance right between insulation and ventilation. Maybe your buddy nailed that balance without realizing it?
You make a solid point about ventilation, but I'd argue that spray foam insulation can actually amplify humidity issues if not done carefully. I've seen several cases where homeowners relied too heavily on the sealing properties of spray foam and underestimated the need for controlled ventilation. One homeowner I worked with had their attic completely sealed with spray foam, thinking it would solve their moisture problem. Instead, they ended up trapping humidity inside the building envelope, creating condensation issues that weren't there before.
Fiberglass insulation, on the other hand, is inherently permeable and allows moisture to escape more easily—assuming there's proper airflow in place. Spray foam's strength can sometimes become its weakness if airflow isn't carefully considered and managed. It's not just about balancing insulation and ventilation; it's also about recognizing that different insulation materials behave differently under similar conditions. Spray foam definitely has its place, but it requires a more deliberate approach to humidity management than traditional insulation methods do.
