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What is EPDM Rubber Roofing Membrane?

More roofing definitions

Ethylene propylene diene terpolymer (EPDM) is a petrochemical-based rubber used in the manufacture of roof coverings. It has been in use for about 20 years and has proven to be highly weather-resistant. Rubber membrane, as with TPO membrane, is popular for low-slope and flat roofs where thin coverings are preferred. This polymer has low-temperature flexibility as well as ozone, ultraviolet, weather, and abrasion resistance.

How Is EPDM Made?

EPDM is a single-ply sheet made of a synthetic rubber composed of polymers, carbon black, process oil, zinc oxide, and curing agents. The resin is used to produce sheets of the membrane in widths as large as 50 feet with lengths from 50 to 200 feet. It comes in black or white-on-black with the dark color being more light- and heat-absorbent - much preferred in colder climates. The white-on-black EPDM membrane reflects light and heat and so is more popular in warmer climates where keeping residences cool is a priority.

Types of EPDM Rubber Roofing Membranes

EPDM membranes are available with or without a reinforced center layer of polyester scrim fabric. It may be installed using ballast (usually small stones), mechanical fasteners or adhesive systems. Some rubber membranes are manufactured with an adhesive tape already applied to one edge making installation easier.

Costs for EPDM membrane run from 50 cents to $1.50 a square foot while the white-on-black material is more expensive. Membranes with pre-applied adhesive and/or tape cost more. Do-it-yourself kits are sold for handy homeowners but securing appropriate tools can add to the cost of the material.

Warranties on EPDM Membrane

Limited warranties are offered by rubber membrane manufacturers - some at an additional cost - for ten to 15 years.

EPDM Ratings

Rubber roofing membrane is rated on its ability to reflect light and heat using the Solar Reflectance Index. According to the U.S. Environmental Protection Agency (EPA): "Solar reflectance is a measure of the ability of a surface material to reflect sunlight - including the visible, infrared, and ultraviolet wavelengths - on a scale of 0 to 1."

Common Problems

Early EPDM membranes used overly volatile oils which caused excessive shrinkage in the product after being heated by the sun. Less volatile oil is now used to avoid this problem. Other issues include seams becoming unsealed and allowing water in, and moisture forming under the membrane on roofs with air-conditioned spaces beneath.

Environmental Impact of EPDM Membrane

Black and white-on-black membranes have proven to contribute to efforts to reduce energy use as they reflect light and heat from the sun. In both cases, rubber membranes reduce furnace and/or air conditioner use making homes with that type of roofing more energy efficient.

The manufacturing of rubber roofing membranes requires less energy than other roofing materials. Related products - such as adhesives - have been developed to limit or reduce the emission of volatile organic compounds during installation.

As a petrochemical-based product, EPDM does pose landfill problems when used membranes are dumped. Efforts to recycle EPDM into the manufacture of other products may reduce the impact of rubber membranes on landfills.

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