PVC Versus TPO

TPO and PVC have a lot in common. Both are heat weldable roof systems that are typically white in color and have been around for a while. Their specifications are also similar and both roof systems come with warranties varying from 15 – 30 years in length. In addition, most manufacturers can make TPO and PVC in a variety of colors, sometimes even custom colors.

So what’s the difference?

Polyvinyl Chloride, PVC, is known for being one of the original single-ply roof systems and is typically a rigid product. It was first introduced to the United States in the 1970s and initially had a bad track record. Think of a PVC pipe or PVC trim on a house: that is PVC in its natural state. However, in order to make PVC flexible, plasticizers are added to the membrane. Problems can occur from the addition of these plasticizers when they leach out of the membrane in a process called “plasticizer migration.” This causes the PVC membrane to shrink, shatter and crack over time. In fact, some of the first generation PVC roof systems, which were not reinforced, would completely shatter like glass. 

Today, modern PVC roof systems manufactured by reputable companies have greatly reduced the problem of plasticizer migration. In many cases, this problem has been reduced from entire roofs failing to just minor cracking and shrinking after decades of use. Some PVC manufacturers have even substituted typical plasticizers for KEE: an alternative ingredient used for thermoplastic processing which doesn’t have the same plasticizer migration problem. However, KEE membranes are typically far more expensive than standard PVC membranes making them even more expensive than TPO membranes.

When it comes to chemical resistance, PVC maintains an edge over TPO. PVC is the best single ply product available on roofs with heavy grease, oil, and ponding water because it is not as easily worn down. Some PVC manufacturers even warranty their products against these problems when all other roof systems, including TPO and EPDM, have specific exclusions against these items.

In contrast, thermoplastic polyolefin, TPO,  is known for being one of the newer products in the roofing industry. It was first introduced to the United States in the mid-1980s and quickly built traction as a less expensive alternative to PVC. It has similar resistance to chemicals such as greases and oils like PVC, however, PVC maintains an advantage. On the other hand, TPO is far less expensive than PVC and is known to have a similar lifecycle and warranty.

One of the biggest advantages to TPO over PVC is that TPO does not have a problem with plasticizer migration. As a result, TPO doesn’t shrink, shatter or crack over time. 

Another advantage that TPO enjoys is that PVC cannot be installed or patched using self-adhered cover strips, RUSS strips, etc.  As a result, the metal color choice is limited to PVC clad metals. Also, some installation details are limited on PVC roof systems. TPO, on the other hand, can be installed using these products. As a result, edge metal color selections are greater because standard Kynar metal can be used.

With a majority of projects where greases, oils, and ponding water are not a concern, TPO is typically the chosen installation over PVC. If there are no hazardous products on the roof that will jeopardize the TPO membrane, It is hard to justify the additional cost of PVC membrane along with the installation and edge metal color restrictions. Even on roofs with these issues, grease guards can be used to prevent these chemicals from getting on the membrane.

As a result, in the battle of the two heat weldable membranes, TPO wins and is installed almost three times as much as PVC.

Need help with TPO installation or determining the most cost-effective and durable roofing for your building? Give Chaffee Roofing a call so we can walk you through making the best choice with the least amount of stress.

Written by Peter Chaffee

Leave a Reply