I'm renovating my 1980s house and I'm torn between rock wool, wood fiber, and polyurethane panels. My budget is tight but I really want to improve my energy consumption. What would you recommend based on value for money?
Don't get suckered in by the lowest price alone - rock wool is decent for the bang for your buck, but it absorbs moisture and that can become a real problem in an 80s house that doesn't necessarily have good ventilation. Wood fiber breathes better with water (it can regulate it without rotting), so for an old renovation it's often smarter in the long run even if it costs a bit more upfront. If your real concern is just budget and you need to choose now, rock wool does the job, but make sure you check your air sealing first - otherwise you'll have heat loss even with good insulation.
It's not really about picking just one material - it depends mostly on where you need to insulate and what your current situation is. For a reno from the 80s with a tight budget, rock wool is still your best friend: cheap, easy to install, it does the job properly and holds up well over time. Wood fiber is nice if you want something more "eco-friendly" and it insulates better acoustically, but it costs more to install for the same performance.
Polyurethane is overkill for most people - excellent insulation but the price shoots up and honestly for a house like yours, you'll hit your energy goals way before you'd need to go that route without breaking the bank. If you need compactness (like really low attics), then it becomes worth considering, otherwise honestly forget about it. I'd say rock wool everywhere you can, period - you'll get better ROI on your budget that way.
For value for money, rock wool is really the best choice - it's cheap, it's easy to install so you save on labor costs, and the thermal performance is very solid for renovating an old house. Wood fiber is nice if you have a bit more budget and want summer/winter comfort, but honestly for an 80s house with a tight budget, you won't feel a huge difference compared to rock wool. Polyurethane is overkill for your situation - super high-performance yeah, but the price shoots up fast and you'd only really justify it if you need to minimize thickness (like in really cramped attic spaces). Go with rock wool, just make sure it's installed properly without thermal bridges, and you'll already have made a massive jump in energy efficiency.
About rock wool that keeps coming up - I agree it's the best price-to-performance ratio for a lot of situations, but you really can't overlook the moisture issue. In an 80s house without modern ventilation, that can cause problems down the line. Wood fiber costs more but it handles humidity better and it's less of a hassle for future repairs. If your budget is really tight, stick with rock wool but put in a proper ventilation system at the same time - otherwise you'll insulate all you want and you're just going to trap the moisture inside and it'll rot slowly.
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