This article has been written to help time-poor but environmentally conscious homeowners and small business bosses make an informed choice about flat roofing materials.
Divided into sections, it looks at five common flat roofing products and examines their energy efficiency in terms of three things: insulation, projected life-cycle and manufacturing process.
Ethylene Propylene Diene Monomer Rubber (or EPDM)
Please don’t be put off by the scary sounding name. EPDM is simply a rubber roofing sheet that is manufactured from Ethylene, Propylene and Diene. The ‘M’ stands for Monomer, a grade of rubber. A feature of EPDM membranes is that they have far fewer joints than traditional roofing systems. Where joints do occur, because the system expands and contracts, there are no weak points.
The quality of EPDM roofing varies hugely from one manufacturer to another. Some products, typically designed for the DIY enthusiast, are just 1mm thick. However, more advanced EPDM membranes – including those usually used by flat roofing professionals – can be up to 2.5mm thick.
Generally speaking, higher quality EPDM membranes will last up to 30 years, making it one of the most robust flat roofing solutions. However, the jury is very much still out when it comes to the lower quality EPDM products.
Thicker EPDM membranes should also be more resistant to cold temperatures, therefore helping to reduce heating bills. Equally, no heating or welding is required to install EPDM membranes, therefore reducing the energy requirements during installation.
So far, so good. Unfortunately there is a downside. EPDM is manufactured using a fossil fuel, namely petroleum, as its base. As a result, during manufacture, toxic gases are released into the environment. And, worst of all, the recycling of EPDM is not considered viable due to cost.
Sustainability Score: 5/10
TPO membranes are single-ply roof membranes constructed from Ethylene Propylene rubber. They have the durability of EPDM rubber (see above) combined with the performance of hot-air welded seam systems. Many manufacturers claim that TPO membranes are as much as three to four times stronger that EPDM’s adhesive and tape systems.
Typically supplied in a thicknesses of either 45mm or 60mm, TPO is extremely durable, flexible and highly resistant to tearing. TPO roof systems have service lives ranging from 10 to 20 years.
TPO roofing membranes do not use polymeric or liquid plasticizers. Equally TPO does not contain chlorine and no chlorine-containing ingredients are added during the production. It is therefore considered by many to be more environmentally friendly than other membranes.
During the production process, TPO membrane is 100% recyclable. Therefore, the membrane can be re-worked and re-used in the installation process. br>
Sustainability Score: 8/10
PVC membrane is a single ply roofing membrane composed of only one layer of material: polyvinyl chloride. Available in thicknesses between 40mm and 80mm, the PVC membrane is welded together with hot air to eliminate all seams.
PVC roofing systems typically deliver excellent thermal performance, whilst also reflecting nearly 90% of the sun’s heat. It is a highly flexible material that offers excellent roofing protection.
However, there is a downside. Over time the plasticizers in PVC roofs will leach out, meaning they won’t last forever.
A PVC roof is only made up of 50% fossil fuel, namely natural gas or methane. The other half is chlorine, derived from rock-salt. PVC can also be recycled which means both the manufacturing and installation process carry some environmental benefits.
Sustainability Score: 6/10
Cold liquid applied resin
In recent time, liquid waterproofing solutions have been introduced to the market to be used where more traditional methods prove difficult because of complicated layouts or where roofs cover multiple surfaces.
One of the advantages of a liquid applied resin is that if the existing roof is structurally sound, there is no need to strip the existing waterproofing. The resin is applied to the roof cold, with no need for heat, therefore reducing the energy consumed during installation. It is both UV resistant and exceptionally strong, and expected to last up to 20 years. It is also quick and easy to install.
Sustainability Score: 7/10
Green Roofing Systems
A green roof can described as a roof structure that has had a planting scheme introduced. This means that it is covered in something natural, be it turf, wildflowers, lavender, chamomile or Icopal Sedum Mat. The latter is currently very popular as it is very tolerant to dry conditions and can be sustained through natural rainfall alone. On a purely aesthetic note, it also changes colour through the seasons. And not many roofing products can claim that.
In addition to being visually attractive, green roofing systems offer the following benefits:
Environmentally friendly and sustainable
Collect and absorb rainwater
Acts as insulation to the building beneath
Have a low structural demand
Require little maintenance
Although ideal for a flat surface, you can add a green roof to any pitches up to 30 degrees or so by introducing roof battens and edge restraints to keep everything in place.
However, please bear in mind that you can’t just lump a load of turf on your roof and be done with it. A green roof requires several layers including membrane protection, some sort of drainage, a growing medium and the planting itself.
Sustainability score: 9/10
So, there you have it: A simplified breakdown of the various flat roofing materials and how sustainable they are. Green roofing systems are the most environmentally friendly but they may not be practical or appropriate for all. In that scenario, perhaps consider TPO for your flat roof.
Either way, don’t think that your roof cannot be sustainable. There are definitely eco-friendly roofing products out there for you, whatever your requirements.
Article by Will Strauss, a freelance journalist based in Leeds, England. A versatile writer, he regularly covers a range of subjects from broadcasting and music to DIY and construction. He is currently working with the Leeds roofing company DPR.