We're doing a loft conversion and our surveyor mentioned fibreglass batts like we used back in 2009. They're cheap but I'm wondering if there's been better stuff invented since then, or if fibreglass is still fine for the job.
Fiberglass batts are still totally fine for a loft conversion in 2026, honestly. Yeah, there's been some incremental improvements in insulation tech over the last 15+ years, but we're not talking about anything that's made fiberglass obsolete. The R-value per inch hasn't changed dramatically, and installation methods are basically the same. The main reason your surveyor's probably recommending it is because it works, it's affordable, and installers know how to handle it properly. If cost is a concern for your project, fiberglass remains one of the most economical options out there.
That said, there are a few alternatives worth considering depending on your budget and specific situation. Mineral wool (rockwool) has become more popular and offers slightly better fire resistance and acoustic properties, plus it's easier to work around awkward spaces. There's also closed-cell spray foam if you want maximum insulation value in minimal thickness, but that gets pricey fast. Recycled denim insulation is another option if you want something more eco-friendly, though it'll cost more than fiberglass. For most loft conversions though, if your surveyor's suggesting fiberglass and your budget isn't huge, I'd say go for it. Just make sure whatever you use has a proper vapor barrier and good ventilation to avoid moisture issues - that matters way more than the specific insulation type.
One thing I'd double-check: make sure you're meeting current building regs for loft conversions. Thermal requirements have gotten stricter since 2009, so you might need a thicker installation than what you did back then, but fiberglass can absolutely meet modern standards if you layer it properly.
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