Is R49 good for an attic?

Yes, R49 is considered very good for an attic and is the target R-value recommended by Energy Star and the International Energy Conservation Code for most climate zones 4 through 8, which covers the majority of the United States. R49 in an attic typically requires about 13 to 14.5 inches of blown cellulose or 16 to 18 inches of blown fiberglass, and it provides excellent resistance to heat loss in winter and heat gain in summer. Compared to older homes that often have only R-19 or less, upgrading to R49 can reduce heating and cooling costs by 10 to 30 percent, improve comfort by reducing drafts and cold ceilings, and help prevent ice dams in winter by keeping the roof deck colder. R49 is considered the sweet spot where you get most of the energy savings without the diminishing returns of going to R60, though in very cold climates like Minnesota or Maine R60 is even better. To achieve true R49 performance you must also air seal all penetrations, ensure proper attic ventilation, and install insulation without gaps or compression, otherwise the effective R-value will be lower than the nominal rating.