I live in a house built in the '90s, and the ceiling in the attic isn't insulated at all. In winter, the heat loss is absolutely crazy, and my heating bills are huge. What should I choose - mineral wool, cellulose insulation, or maybe clay pebbles? And what thickness should I go for?
Expanded clay works well if you lay it down in a thick layer - about 20-30 percent thicker than what's recommended for mineral wool - plus it doesn't compress, isn't bothered by moisture, and lasts forever. The downside is it's heavier, so you need to make sure your beams can handle the weight. If your attic has good ventilation, then expanded clay is a solid choice for your situation - you pour in 20-25 cm and forget about it for twenty years.
Mineral wool and eco-wool are both good options, but I'd lean toward mineral wool just because it's cheaper, lasts longer, and doesn't compress over time. Eco-wool requires special spraying equipment to do it right, whereas you can lay mineral wool yourself between the joists. Expanded clay is heavier and requires reinforcing the ceiling structure, plus it's harder to lay evenly in the attic. For central Russia, a thickness of 150-200 mm is usually enough - that's roughly when you start seeing serious heat loss reduction.
The key thing when laying it down is not to forget the vapor barrier on the inside of the house and attic ventilation. If you just throw mineral wool down without a vapor barrier, it'll absorb moisture from the heated room, lose half its properties, and end up wet every winter. It's best to lay it between wooden joists - then you don't need extra framing. Having access to the attic will obviously make the job easier, but if the attic's unheated, there's nothing complicated about it.
Calculate it like this: house → vapor barrier film → mineral wool layer → ventilation gap (at least 5 cm) → roofing. If you insulate properly, your heating bills will drop by 20-30 percent - that's genuinely noticeable.
Before you choose a material, check what condition your attic is in - often the problem isn't a lack of insulation but gaps and vents that undo all your efforts. If your attic has good ventilation (which you need for air circulation), it makes sense to combine approaches: lay a vapor barrier on the bottom, then a layer of mineral wool about 15 - 20 cm thick, and on top of that add some expanded clay or sawdust - it works as a thermal accumulator and is cheaper than filling everywhere with mineral wool alone. Calculate the thickness based on your region's climate, but usually 20 - 25 cm is enough for the central belt.
When I was renovating my house, I ran into the fact that mineral wool is a good choice for price and durability, but there's one thing people often miss: if you lay it straight on wooden beams without a vapor barrier, condensation will build up in the fibers and the wood will start to rot. You definitely need a layer of vapor barrier film on the house side, otherwise you'll have problems in five to seven years. For thickness, they usually recommend 15-20 cm for the middle latitudes, but it's better to check for your region - some people might need more. Ceramic aggregate is cheaper, but denser and takes up more space in the attic, and blown-in cellulose without spray application is a hassle to lay by hand, and gaps form easily.
The first thing to do is sort out your attic ventilation, because even the most expensive insulation won't help if there are drafts coming through gaps and the vents aren't working properly. After that, you should definitely choose between mineral wool and cellulose insulation - both work, but mineral wool is more practical for DIY installation and cheaper, while cellulose insulation requires special spraying equipment.
As for thickness, it depends on your region, but usually 15-20 centimeters is enough to significantly reduce heat loss. The key thing when laying mineral wool is to use vapor barrier on the warm side of the room, otherwise moisture will condense in the insulation itself and it will settle and lose its properties.
I wouldn't skimp on the thickness - for a house built in the '90s in the middle zone, you should aim for at least 15-20 cm, or ideally 20-25 cm, otherwise the effect won't be very noticeable. Mineral wool is more convenient than expanded clay in this regard, because it's easier to lay it down in an even layer of the right thickness. As for ecofiber, I'd leave that for if you have the ability to call in specialists with equipment - it's pretty hard to install it yourself.
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