Went through something similar myself—thought I was being clever by layering polyiso on my flat roof. Worked great until we hit one of those brutal February cold snaps. Suddenly, my furnace was working overtime and my wallet was crying uncle. Switched to EPS the next year, and while it didn't exactly blow me away on paper, it kept things steady when winter got cranky again. Sometimes boring is good...especially when your heating bill's sanity is at stake.
Interesting experience—I've seen a lot of folks go down the polyiso route thinking it's the silver bullet, only to find out the hard way that cold snaps can really throw a wrench in things. Did you notice if moisture was an issue at all when you switched over to EPS? Sometimes polyiso can lose its insulating value when temps drop significantly, but I've also heard mixed things about EPS and moisture retention.
Also curious, did you consider XPS at any point? I've had a couple of clients who swear by it, especially for flat roofs. It's not exactly the cheapest option, but they seem pretty satisfied with how stable it stays in extreme weather. Then again, every roof seems to have its own personality, doesn't it?
Glad you found something that works though—nothing worse than seeing your heating bills spike overnight and feeling like you're just tossing money out the window. And you're right, sometimes the less flashy solutions end up being the most reliable in the long run. Did you end up doing anything else differently with your roof setup after making the insulation switch, or was EPS enough to keep things steady?
Either way, sounds like you made a smart move. Roof insulation can be tricky business... trial and error is pretty much par for the course.
"Then again, every roof seems to have its own personality, doesn't it?"
Couldn't agree more with this. I've seen EPS perform surprisingly well in situations where polyiso struggled, especially during those nasty cold snaps. Moisture-wise, EPS can hold up pretty decently if installed correctly—key phrase being "installed correctly." I've noticed that a lot of moisture issues come down to improper sealing or inadequate vapor barriers rather than the insulation itself.
As for XPS, it's definitely solid stuff, but the environmental concerns around blowing agents have made me hesitant to recommend it lately. Plus, price-wise, it can be a tough sell for some homeowners. Still, if budget allows and you're looking for something stable in extreme conditions, it's hard to beat.
Glad you found EPS working out for you though. Sometimes the simpler solutions really do end up being the most reliable... and easier on the wallet too.
You're spot on about installation being the real deciding factor. I've seen roofs with premium insulation fail miserably just because someone skipped sealing a few seams properly. EPS can definitely surprise you—had a building last winter where EPS held up great, while a pricier polyiso setup next door had condensation issues. Like you said, sometimes simpler really is better... and cheaper too. Glad it worked out for you.
"sometimes simpler really is better... and cheaper too."
I get where you're coming from, but honestly, I've had mixed experiences with EPS. Had a property a few years back where we went with EPS insulation because it was budget-friendly. Installation was done carefully, seams sealed tight, the whole nine yards. But after a couple of harsh winters, we started noticing some moisture buildup anyway. Not saying EPS can't work—clearly it did for you—but I wouldn't dismiss polyiso outright. Sometimes pricier materials do pay off in the long run... just depends on the building and climate, I guess.
