The Insulating Value of Carpet Padding

R Values

• In the building and construction industry, a material's R value is a measure of its thermal resistance. A higher R value provides greater insulation from both interior and exterior temperature changes. It can also help absorb and block sound transfer between floors. Each type of carpet padding is assigned an R value that can range as low as 0.2 to as high as 2.1 R. Carpet also carries its own R value. Once the carpeting is laid on top of the carpet cushion, the two combine for a greater overall insulation value.

Polyurethane Foam Padding

• Polyurethane foam padding is made by combining liquid ingredients into a foam mass which is cured and then sliced into large sheets for use as carpet underlay. A recycled version known as bonded foam or rebond foam is made from recycled scraps that are shredded and rebonded together. Polyurethane foam padding can vary in thickness anywhere from 1/4 inch to 1/2 inch thick and offers an R value from 1.11 to 2.10 R.

Sponge Rubber Padding

• Sponge rubber carpet pads are made from synthetic rubber and come in both flat and waffled versions. Flat sponge rubber is firmer and more dense, which is preferable for interior sound insulation between floors. The waffle design's natural air pockets interrupts thermal transfer and thereby provides a higher R value. Sponge padding is measured according to weight from 56 to 100 ounces. Depending on weight, a sponge underlay can provide an R value ranging from 0.21 to 0.67 with the waffle rubber scoring higher.

Fiber Padding

• Fiber padding can be made of new or recycled fibers. Natural fiber carpet backing is created using natural fibers such as jute, animal hair or felt. Synthetic fiber padding is made from nylon, polypropylene, polyester and acrylic fibers. Like sponge padding, fiber padding is measured according to its weight from 20 to 56 ounces. The 20-ounce fiber padding carries an R value of 0.99 while 56-ounce padding provides an R value of 1.73.

Fiberboard Insulation

• Another option in carpet padding is fiberboard insulation. Made from recycled newspaper, fiberboard insulation is very dense. A 1/2 inch thick fiberboard underlay provides at least a 1.2 R value. It can be installed beneath any traditional carpet padding. The combination of fiberboard with carpet padding and the carpet itself can exceed an R value of 3.0 to provide excellent sound insulation between floors along with superior thermal insulation from concrete slabs and basements.