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An insulated roof, not to be confused with an insulated attic, is another way to prevent heating and cooling losses. The roof insulation is installed on the roof slope, above and below the rafters, while the attic insulation is installed on the ceiling. If your home has a flat roof or pitched roof, roof insulation is especially important. Sealing the roof and adding insulation can protect it from ice dams and other moisture-related problems.

The cost of roof insulation depends on the type of roof insulation material you use, the R value of the insulation material, and the area you intend to cover. There are generally five types of insulating materials used for roofs.

Spray foam insulation usually requires contractors to install, and radiation barriers usually don't provide any R-values, although some companies boast that radiation wall barriers will help maintain heat in the home and form a vapor barrier.

Under certain conditions, roof insulation is important. If the ceiling of the house is part of the roof terrace, just like the cathedral ceiling, it is important to insulate the roof terrace.

Insulating the roof can help prevent ice dams, which form when water re-freezes on the roof after thawing. Ice dams can accumulate huge weight and exert excessive pressure on the roof, causing the roof to collapse.

Since the air-conditioning ducts are usually located in the attic of the house, the insulated roof also helps to keep the slab house cool in warm climates.

If you plan to complete the attic and turn it into a living space, then you need to install roof insulation to control the temperature fluctuations that the attic usually experiences.

The R value is a number related to the insulation protection level. The higher the R value, the better the protection. When looking for insulation materials, the R value is very important, because different climate zones have different R value recommendations for insulation materials. In addition, the higher the R value, the higher the cost.

If the space is used for other purposes than storage, insulating the sloped sides of the pitched roof can help save heat. The cost is the same as other insulating materials—0.50 to 1.50 US dollars per square foot, and approximately 2 to 2.50 US dollars per square foot for installation.

The average cost of installing insulation on a flat roof is approximately $0.67 per square foot, using a 1-inch thick PolyISO with an R value of 6. When considering insulation, expect to pay about a quarter of the price to install a flat roof. Remember, the thicker the insulation board, the more expensive the project.

The roof insulation is installed on the roof slope, above and below the rafters, while the attic insulation is installed on the ceiling.

The US Department of Energy recommends using at least 11 inches of rock wool or glass fiber insulation or 8 inches of cellulose.

Attic insulation is considered easier and cheaper than roof insulation.

Nick is a content creator with a background in DIY home improvement, maintenance, repair and trends. When he is not writing, Nick likes to restore retro or kitsch furniture for his home.

Samantha is an editor, covering all home-related topics, including home improvement and maintenance. She has edited home repair and design content on websites such as The Spruce and HomeAdvisor. She also hosted videos about DIY home tips and solutions, and launched a number of home improvement review committees equipped with licensed professionals.