Polyester Vs. Fiberglass Insulation

Updated February 21, 2017

Insulation is put into buildings to make them more energy efficient. It keeps your home cool in the summer and warm in the winter. A properly insulated home uses less energy for heating and cooling. Fibreglass is the most commonly used insulation material, but polyester is growing in popularity, especially among those who want to install the insulation themselves.

Properties of Material

Polyester is a man-made synthetic fibre that is oil-based. Polyester insulation does not burn easily, but it will give off dense smoke.

Fibreglass is made up of natural ingredients such as sand, plus recycled products such as window glass and bottles. The ingredients are melted down, and then spun into small strands to form a glass fabric. Fibreglass does not burn, but it can melt in the intense heat of a house fire.


Polyester is two to three times more expensive than fibreglass.


The main complaint people have about fibreglass has to do with its installation. It can cause irritation of the skin and respiratory tract. Also, formaldehyde is used as a curing agent in the production of fibreglass, and it emits fumes when the fibreglass is first used.

Polyester insulation causes no skin or respiratory irritation, and it omits no gaseous fumes.

Environmental Impact

The production of fibreglass requires an energy-intensive manufacturing process. Manufacturers use up to 40 per cent recycled materials to produce it, and of those materials, 20 per cent to 30 per cent is recycled glass. Used fibreglass is not recyclable.

Because polyester insulation is made from oil, which is a non-renewable, finite resource, environmentalists are concerned about its use. Like fibreglass, it is not recyclable and must be placed in a landfill at the end of its useful life.


Heat is a form of energy that always seeks a cooler area. It flows out of the home in the winter and into the home in the summer. R-rating is the scale used to judge how well insulation resists the flow of heat. Polyester’s R-rating is considered equivalent to that of traditional fibreglass, and it has similar sound absorption abilities. Fibreglass’s approximate R-rating is R-7, and polyester has an R-6 to R-9 rating.

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About the Author

J.M. Pence has written magazine articles and essays for a variety of publications, including “Sunset,” “Mystery Scene,” “Cat Fancy,” and “Idaho Magazine,” plus 15 novels, a novella, and several short stories. Published since 1987, Pence holds a master's degree in journalism and a B.A. in history with a minor in political science from U.C. Berkeley.