Best Insulation for Ceilings

Updated March 23, 2017

Insulation for a ceiling is one investment that is worth every penny. Proper insulation blocks winter's cold air and summer's heat from entering the house. Selecting the wrong insulation results in trapped moisture and eventually mould build-up. When considering the best insulation for a ceiling, you must consider both the ceiling type and the insulation. Insulation is rated by R-value, which is a measure of how well the insulation resists heat flow. A higher number means better insulation.

Standard Attics

Standard attics with straight rafters are the least expensive to insulate with the best results. Loose fibreglass fill is sprayed between the rafters and is both fire and moisture resistant. It fits perfectly into tight spaces, so it also can be used to retrofit a poor insulating job and has an R-value of 4. While fibreglass cannot decay, it does require a vapour barrier to prevent water damage.

Cathedral Ceilings

The only insulation recommended by This Old House for cathedral ceilings is foil-faced polyisocyanurate. These rigid sheets covered with foil act as both insulation and a radiant barrier. It is non-flammable and has an R-value of between 7 and 8. While it does not require a vapour barrier, it does require a wallboard covering.


Pipes running through roofs and attics are often neglected when it comes to insulation. This is a mistake that can cost homeowners large amounts of money should the pipes ever sweat. The best insulation for roof and attic pipes is by far rigid insulation. Rigid insulation is a board-like insulation form that companies custom mould to fit around pipes. It has a higher R-value for small spaces than most other forms of insulation and is typically covered with a radiant barrier to block even more heat.

Hot Climates

For hot states such as Nevada and Arizona, radiant barriers offer the most insulation benefits hands-down. The barrier is designed to directly block heat and can be installed to either an attic's rafters or floor. Best of all, it is completely fire proof, will never settle and reduces a home's cooling costs by up to 30 per cent.

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About the Author

Steven White is a privately contracted software engineer and efficiency analyst. He has more than five years of experience providing technical support for AT&T broadband customers. Along with his technology background, White enjoys carpentry and plumbing.