Last fall, I bought foamed polyethylene here for the country. The material is non-toxic, cheap and high-quality, that's why I took it. It was very warm in winter. By the way, it was not difficult to insulate yourself. It was delivered very quickly.
We bought foamed polyethylene in Poriflex to insulate a house in the village. We have never regretted it! The consultants correctly explained how much material would be needed and where to pick it up)
Now the house is warmer and the audibility from the street has noticeably decreased)