We're currently renovating our house from 1978 and don't know whether we should go with stone wool, glass wool, or polystyrene. Energy prices are still high and we want to do it right. What would you guys recommend?
For your old building renovation, I'd recommend mineral wool - it's got good thermal performance, is relatively cheap, and handles being near welding better if you ever need that. Fiberglass works too, it's just a bit itchy to work with. Polystyrene is cheaper, but for a proper renovation in 2026 I'd go more for the mineral fibers because they're just more durable and deal better with old building structures. But the most important thing is that you seal the joints properly and don't have any thermal bridges - you'll save more money on that in the end than by picking between materials.
I've had pretty mixed experiences with that. During my own renovations, I found out that it really depends on where you want to insulate - for the facade I'd lean more towards mineral wool because it's more durable, but under the roof or for internal insulation polystyrene can make sense too, especially when space is tight and you don't have much room. Energy prices are still pretty high, that's true, but trust me, it pays off if you do it right. My tip: get a tradesman to come by and take a look on site, they can tell you way better what works for your '78 period building - every house is a different project.
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