The most accessible and affordable home insulator is rolled fiberglass, and the most effective insulator is closed cell foam, according to HGTV. Cotton batts are a comparable option.
Fiberglass batts are the industry standard in home construction. They are the cheapest insulator on the market, may be purchased at any home improvement store and do not require professional installation. The downsides of fiberglass insulation are the hazardous fibers that are released into the air during installation and the challenge of installing it in small spaces or around electrical and plumbing fixtures.
Cotton batts are very similar to fiberglass batts, but they are made from recycled denim. Cotton provides better soundproofing than fiberglass; however, it is slightly more expensive. It has many of the same pros and cons as fiberglass batts, but it does not release hazardous fibers into the air.
Spray-in foam insulation provides superior draft protection and insulation. Open cell foam is the more affordable option, but closed cell foam is the best insulator. Both options are far more expensive than fiberglass batts, but if home energy costs are high, the higher-quality insulators may be worth the investment over time. The disadvantage of closed cell foam is that it must be cut away to make any changes to the plumbing or electrical wiring.