Whether you are a business or homeowner looking to install a new flat roof, you have a number of choices to consider: EPDM Rubber, PVC and TPO roofing systems. While all of these membranes are single-ply roofing systems, they are actually very different in their formulations, manufacturing process, durability, longevity and performance.
This guide is a detailed comparison between EPDM Rubber which is the cheapest and therefore most commonly used flat roofing system and PVC roofing membrane, which is a premium product that costs more, but offers superior protection.
EPDM ROOFING VS PVC ROOFING
What is an EPDM rubber roof?
An EPDM rubber roof is the most popular and economical single-ply roofing membrane that has been in wide use for over 40 years. EPDM (ethylene propylene diene monomer) is a type of synthetic rubber. This rubber is made up mostly of oil (carbo-hydrate) based by-products with modifiers and stabilizers added to extend its service life. An adhesive is used to glue the roof to the roof deck and special tape is used to seal the seams.
An EPDM roof is designed to be UV stable and to withstand inclement weather, ozone and heat. The roof is also resistant to tear, puncture, impact, and normal roof traffic. An EPDM roof is able to accommodate structural movement and remains pliable under a wide range of temperature fluctuations. No special equipment is required to install an EPDM rubber roof.
What is a PVC roof?
A PVC roof was first manufactured in Europe in the 1960’s, but quickly made its way to the US. Initially, this membrane was designed to address the shortcomings of EPDM rubber roofs. PVC (polyvinyl chloride), typically called vinyl, is made up of ethylene and chlorine. In the manufacturing process, biocides, plasticizers, ultra-violet light inhibitors, heat-stabilizers, color pigments and polyester or fiberglass reinforcement are added to enhance stability and flexibility, as well as achieve high tearing and breaking strengths. A PVC membrane is made up of two plies of PVC material with a polyester reinforcement scrim in between. Distinctive to PVC membrane, making it more durable than EPDM are hot-air welded seams.
A PVC roof is a premium single-ply roofing membrane, with superior durability, longevity and performance, and therefore costs more than an EPDM rubber roof. Hot – air welded seams make the membrane pliable and watertight under a variety of extreme weather conditions. A PVC roofing membrane is highly resistant to constant dampness, ponding water, as well as high and low alkaline conditions. A PVC roof is also resistant to UV radiation, strong winds, fire and chemicals. Plant roots, fungi and bacteria have no negative affect on a PVC membrane.
LONGEVITY OF EPDM VS PVC
An EPDM roof is designed to have a service life of 12-25 years when properly installed. However, EPDM rubber roofs often begin to leak and even fail prematurely way before the projected end of their service life for reasons outlined in the Second Part of the Comparison Guide. Black EPDM roofs carry a 20 year warranty on membrane only against weatherability and factory defects. White on black EPDM roofs have a 10 year warranty on membrane against weatherability and factory defects.
PERFORMANCE OF EPDM RUBBER VS PVC
EPDM: Residential Applications
One of the biggest problems with EPDM rubber roofs is that many of them begin to leak and fail much sooner than their expected service life ends. Most rubber roof failures occur as a result of a combination of inherently flawed membrane design and poor installation. Typically these failures occur at roof penetrations, flashing and seams.
An EPDM rubber roof is designed in a way that flashing material needs to be glued around the corners and around roof penetrations with a special adhesive. This presents a problem from the outset, because this adhesive will eventually fail and the seams will start coming apart. To prevent this issue from happening or to repair it, an EPDM rubber roof needs repair at the seams, process known as “reseaming”.
Another related issue is that many roofing contractors who install an EPDM rubber roof do not allow enough time for the flashing material to stretch during the installation. As a result, the flashing self -pulls, breaking the adhesive. This in turn creates areas where water and moisture can easily penetrate the roof and damage it, also requiring repair, or in worst cases roof replacement. Faulty installation may cause a rubber roof to leak rather unexpectedly and very shortly after the new roof has been installed.
Why do EPDM rubber roofs have these installation problems? The reason is simple: while proper installation does not require any special equipment, it does require specific technical knowledge and skills. However, despite the fact that an EPDM roof is a specialized type of roofing and therefore should be installed by expert flat roofing installers, it is instead usually installed by general roofing contractors who primarily have experience with asphalt shingles roofs. Ironically, general contractors are able to take on EPDM roofing installation and repair jobs, which they are not qualified to do, precisely because EPDM roofing does not require any special expensive equipment. This is a big issue in the residential flat roofing market, as all the expert installers typically deal with commercial and industrial installations, and do not take on small residential flat roofing jobs.
PVC: Residential Applications
By comparison, PVC roofing membranes are designed to be watertight and actually remain leak-free for decades of service. The reason for such durability is the hot -air welded seams used to bond together the membrane’s sheets. These seams create a super strong, permanent bond that does not allow any leaks to come through even in times when there has been ponding water sitting on the roof for many days. If at any point, problems with seams arise, it is very easy to fix them by simply rewelding the seams.
Unlike EPDM rubber roofing, PVC roofs are typically installed by professional contractors who have knowledge and experience with PVC roofing membranes. This difference is due to the fact that installation and repair of PVC roofs requires specialized equipment, which is very expensive. Only specialty contractors who are in the business of installing PVC roofs are willing to invest money into all the necessary equipment. Consequently, these contractors are also trained to have all the technical skills required for installation and repair of PVC membranes. This means you can be a lot more confident that a PVC roof has been correctly installed on your home and will provide you with many years of leak-free service life.
When it comes to commercial applications, and especially restaurants, EPDM rubber roofs are vulnerable to all kinds of chemicals, solvents and oils. These may cause irreparable damage to an EPDM membrane, which means that it is best not to install it over buildings that are likely to have chemicals, grease and oils on the roof.
By contrast, PVC roofing membranes are specifically designed to be highly resistant to damage from chemicals, solvents and oils. This feature makes PVC roofs ideal for restaurants, and any commercial and industrial facilities that deal with chemicals and solvents.
An EPDM rubber roof is not considered to be an environmentally – friendly roofing material. It is primarily composed of ethylene, propylene and carbohydrate byproducts of oil refining. Therefore, EPDM rubber roofing directly contributes to our dependence on oil, and green-house gas emissions. Moreover, an EPDM rubber roof cannot be recycled and has to be disposed as waste in a landfill.
On the other hand, while PVC roofing is not a truly “green” roofing material, it is more eco-friendly than EPDM rubber. While fossil fuel is also involved in the manufacturing of PVC, less of it is required (only 50%) while the rest is derived from salt. PVC is designed to be a cool roofing system, reflecting up to 90% of sun’s UV rays, thereby helping to reduce energy waste from HVAC systems used to cool buildings, and to decrease the “heat island” effect. Also, PVC can actually be recycled, and is used over again in production of new PVC membranes as material for the bottom ply.