TPO vs EPDM Rubber roofing – singly-ply roofs comparison.

Are you looking for a quality, energy efficient solution for a low slope roof and are not sure whether to go for TPO or EPDM roofing membranes? It can be difficult to distinguish between the two products as both are single ply roofing membranes. However, there are important differences that you need to be aware of to figure out which roofing membrane is right for you. When making your decision consider such factors as cost, longevity, durability, maintenance, ease of installation and energy efficiency. To learn more information about how TPO and EPDM stack up against one another, refer to our comparative guide.

Cost

EPDM roofs are the most economical choice for single ply roofing membranes. TPO roofing membranes are more expensive than EPDM. Regardless of which membrane you choose, it is better to spend more money and ivest into a thicker membrane. Both EPDM and TPO roofs perform better and last longer if they are thicker.

Longevity

By far the most important aspect that will determine the longevity of a single ply roofing membrane is the method by which the overlapping seams have been attached together. Permanently attached seams are the safest solution, and improper attachment can be the cause of 99% of leaks.



It is difficult to determine the longevity of TPO roofing membranes for a couple of reasons. First, this is a fairly new roofing product, there are no TPO membranes in the US today that are older than 15 years. Second, TPO membranes continue to be an experimental products- they are all in their 2nd, 3rd and in some
cases 4th generation of formulations, so it is not possible to definitively say how low any of these will last. Moreover, many TPO products have been pulled off the market in the past both for seam and material failures.

Durability

An EPDM rubber roof has a solid reputation for durability. Made of rubber compound, EPDM roofs have been on the market for decades- having properly tapered seams and detailed flashings, an EPDM roof will last up to 25 years. It is recognized in the industry as a dependable roofing material that offers resistance against ultraviolet light, ozone, oxidants and severe weather conditions. An EPDM membrane will also preform better than TPO in colder climates.

TPO seam strength is 3 to 4 times that of EPDM adhesive and tape seams.TPO membranes are manufactured to be as durable as EPDM. However, because there are continuous changes and improvements to the formulation, different TPO membranes perform differently. TPO is known to respond poorly to ponding water (it splits and cracks) and also does not have strong resistance to heat and solar overload.



Maintenance

In the beginning of its service life, a properly installed EPDM membrane will not require much maintenance. However, unlike TPO ( which has hot-air welded seams) an EPDM’s seams are treated with an adhesive, making them ultimately vulnerable to coming apart. This means that in the long run an EPDM roof will require maintenance to keep in tact. Be aware that EPDM responds very poorly to any kind of solvents and oils. Therefore, you should not use cleaners or conditioners that contain petroleum solvents, harsh abrasives or Citric based cleaners as these may cause irreparable damage to an EPDM membrane.

TPO membranes are not as easy to maintain as EPDM roofing membranes. In general, it is problematic to weld new materials to a TPO membrane, because as compounds age they loose their pliability and their subsequent thermoplastic capabilities. Consequently, to effectively heat weld new material to an old membrane may require an an “activator” similar to hypalon to seal repairs.

Ease of Installation

An EPDM rubber roof is easier and faster to install than a TPO roofing mebrane. EPDM requires no special equipment for installation while TPO needs to be hot air welded. This makes installing a TPO roofing membrane a more complex and costly process that also requires specialized knowledge. While a beginner roofer contractor will most likely be able to properly install an EPDM membrane, you should only hire an experienced contractor to install a TPO roof. Improper installation will invariably cause leaks and will require costly repairs or replacement.

Energy Efficiency

TPO membranes have become an increasingly popular single ply roofing choice because they offer energy efficiency. White TPO membranes are considered to be a “cool” roofing technology, but other colors of TPO are also formulated to have sun reflective properties. With a TPO roof, it is possible to save money of cooling costs of both residential and commercial properties because by reflecting solar heat, a TPO roof is able to maintain a cooler thermal balance inside the space, reducing the need for additional air conditioning. Energy efficiency makes TPO roofs particularly popular in hot sunny regions that get a lot of cooling days.

While EPDM roofing membranes are also available in white and will offer better reflective properties than darker colored EPDM, and EPDM roof will not offer the same level of energy and financial savings as a TPO roof.

Alternatives to both TPO and EPDM:

Although both EPDM and TPO roofs are widely used in commercial flat roofing, there is another product worth mentioning here – it is PVC roofing. PVC roofs have been around almost as long as rubbers, and much longer than TPO. In fact TPO was created to be a cheaper alternative to PVC (to provide all the benefits of PVC, such as cool roof surface, hot air welded seams, etc), while offering just a slightly higher price than EPDM rubber. However with lower price, come issues of quality. Without going into much details (its a topic for an entire separate article, which we will post shortly), TPO has still unproven track record, and has had its share of material / weld failures, and major reformulation by the manufacturers, to fix the problems of first few generations.

PVC roofs on the other hand, have been installed installed in US for 35+ years with only one major issue which was isolated to a specific membrane type made by a specific manufacturer (Trocal), which is no longer in business. Other than that, PVC roofs (such as IB Roof) have great performance, no leaks when installed properly, by certified contractors, and are very easy to repair, even when they are 30+ year old (see video above).

White Roofs

How would you like to come home on a hot summer day and not run to your AC thermostat because you can barely breath in the stifling heat? You may not be aware of it, but the high temperature inside is in great part caused by the dark colored roof of your home or office. This happens because the dark color of the roof attracts the sun and traps this heat inside the house instead of reflecting it back into the atmosphere, in a much the same way as dark clothing makes us more sweaty and hot during the summer. Such heat is particularly an issue and even a health hazard for the elderly and children, especially if they are not able to afford high cooling costs in the summer. If instead you would like your house to be a comfortable 80 degrees F when it is 100 degrees outside, a white color roof is the perfect solution.

What is a white roof?

Dark roofs are typically made of asphalt, tar and modified bitumen, or asphalt-based roofing shingles. These roofing materials absorb as much as 90 percent of the sun’s heat energy. On the contrary, white roofs, which can be made from different types of roofing materials, deliver high solar reflectance (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun), and high thermal emittance (the ability to radiate absorbed, or non-reflected solar energy). As a result, a white roof can absorb as little as 10 percent or 15 percent of the sun’s heat.

Benefits of a white roof

In terms of energy savings for your home, if you use a white roof and you have air conditioning, depending on the geometry of the building, you can save as much as 15% on energy bills by just simply having a white roof. Because white roofs reduce the use of air-conditioning during the day’s hottest periods, the energy savings occur when electricity demand is at its peak. Consequently, if you are a home or building owner and pay for your energy based on the time of use, you save energy when it is at its most
expensive.

In case you are not ready to replace your old dark roof with a new white roof, but still want the benefits of a white roof, consider installing a white roof coating. There are a number of coatings that will substantially improve an existing roof’s reflectance. Additionally, coatings protect and seal, potentially extending the life of your roof. The installed cost of coating a roof is about $0.50 to $1 per square foot. You will definitely see a return on your investment with lower energy bills and the extended life of your roof.

From a more global perspective of helping combat global warming, white roofs and white colored pavements also change the reflectivity or the so called obidal of the earth. The sun comes in and its reflected back into space. There is no green house cap on this. The department of energy has calculated that if you replace all the building roofs today with white roofs and you go to cement style pavement instead of black tops, it would create a reflection of sunlight back into space that would be the equivalent of taking off all the automobiles in the world for 11 years!

If that is not convincing enough, research by the California Department of Energy has found that turning all of the world’s roofs “light” over the next 20 years could save the equivalent of 24 billion metric tons in carbon dioxide emissions. This number is equivalent to what the entire world emits in one year.

White Flat Roofing materials

Most common types of cool white flat roofing materials are PVC and TPO roofing membranes, and to a lesser degree White EPDM (rubber roof) membrane, and white roof coatings (Urethane, Acrylic, etc.).

All of these white roofs are “cool” naturally, because they are white, and reflect a lot more sun light vs black or dark-colored roofs. However, among these white roofs, some actually have COOL Roof label – that is US Department of Energy and other rating agencies and organization consider them to be COOL roofs, which means they meet the criteria for reflectivity and emissivity, and have special reflective pigment in the top coating.

PVC flat roofing membranes offer the longest life-cycle out of the above flat roofing materials. With its hot-air welded seams, a PVC roof can withstand ponding water, and all roof penetrations are flashed with special pre-fabricated roof flashing components. PVC roofs have been installed in US for over 35 years with very impressive track record (except for Trocal PVC roof fiasco which was exclusive to that particular manufacturer).

TPO Roofing are similar to PVC roofs in the way they are installed (also use hot-are seam welding method), but is a much newer system and have spotty track record with many reports of multiple roof manufacturers changing the formulation of their product.

White EPDM roofing is the same ad traditional BLACK rubber roofs, but have white pigment (either throughout the membrane or just top layer). White EPDM roofing has same inherited “problems” of traditional rubber roofs, in that all seams and flashing is sealed with adhesives (chemicals), which fail over time, causing roof leaks. Read more on rubber roofing problems

Government support for White roofs

White roofs have been championed by the US Department of Energy since the 80’s and the trend is slowly catching on. Large corporations such as Wal-Mart have taken advantage of the benefits of white roofs, as more than 75 percent of its outlets in the United States have white roofs. To rein in soaring energy costs, states like California, Florida and Georgia all have adopted building codes that encourage white-roof installation for commercial buildings. Moreover, many state energy offices often offer special financing for white roofs, drawing on federal funds allocated for energy-efficiency projects and green architectural design.

The best part is that if you are educated about white roofs and their benefits and are ready to make the switch, the cost of white vs black roofs is about the same. This is something very simple and something we can start doing immediately to save on our energy bills, improve our health, and help save our planet one white roof at a time.

Flat Roof Repair – Modified Bitumen rolled roofing

Flat roof leaks and flat roof repair are often very different and require professional “look” at the roof leaks issue. For most homeowners, flat roof leaks are very frustrating, because only few roofing contractors have the skill and knowledge to properly diagnose and repair leaking flat roofs.

We often get questions from homeowners about their flat roof leaks and this time we were contacted by one such homeowner from London, UK about his roof leaks, and wanted to share this with you as it might be helpful for many other homeowners with flat roof leaks.



Below is a conversion with Ajay – the homeowner with leaking / damaged modified bitumen flat roof (we’ve attached roof pictures that came with each email):

Hi Leo,
Sorry for emailing you “out of the blue” like this but I found one of your posts on this website (Flat Roof Repair article on CoolFlatRoof.com) and thought I would seek your advice. If you don’t feel comfortable
giving advice to a stranger like this, then I fully understand!

The problem is that my neighbor is doing building work and one of his builder’s scaffolding planks fell into our flat roof and made a
dent/hole in the roof. It’s been two weeks now and they haven’t had the courtesy to fix it and I’m now suspecting there could be water damage as it has rained quite a bit over the past few days (I live in London).

I hope you’ll be able to offer some advice as to what needs to be done to do a proper professional repair. I was thinking of going with the
EPDM option – how should this be sealed? What do we do about the board underneath? Do we go with 2-ply 25mm waterproof marine plywood? I’ve attached photos so you can see exactly what the damage is.

Regards,

Mr Ajay

image of leaking flat roof

 

My response:

Hi Ajay,

Judging from pictures, you have a rolled asphalt roofing OR granular surface modified bitumen (though I think it’s the first one), that is adhered directly over OSB – particle board.

I doubt there is much rot damage, though the in area right around the hole, the OSB composition has probably weakened. Do you have water stains inside?

I think you should talk to your neighbor to have this fixed OR have your insurance company go after your neighbor and the contractor who damaged the roof – this will force them to get the contractor to fix the damages … or something like that.

As for repair – you cannot use EPDM rubber to fix it. You will have to use same or similar roofing material and all seams will be done either with TAR or torch (if it is mod. bit. roof). Tar does not hold too well, but I guess it held so far.

You would need a whole section replaces – not just a patch, as patch will not hold long. Best bet, is to replace the whole thing if possible, as it looks like a “hack job” to me – the seam overlaps are in the wrong direction – they should be facing the roof slope – away from the building. Insetad the face the building, so all water running down, catches seams.

I don’t know about your local building codes, but 25mm (about 1 inch) waterproof marine plywood seem EXCESSIVE to say the least.



Typical roof deck here in US is 5/8 inch 4-ply regular plywood, and “overkill” is 3/4″ … that’s when your rafters are spaced far apart.

Bottom line – most hack roofers will will throw a bunch of tar on top of the hole, maybe a mesh and more tar. This would work for short time (maybe a year or two). The correct way to fix this would be to replace a section, which can tear the adjacent sections … hence I recommend the replacement if possible.

My reasoning is that they damaged your roof, and throwing tar on it will not make it “whole” or in the same condition as it was – it will be merely a temporary fix.

One more thing – you need a professional roofing company to fix this – not the contractor who caused the damage – they have no clue about flat roofing!

I believe I know a company in London … I’ve seen their work on YouTube and the seem to know what’s up.

Good luck.

Sincerely,
Leo – Project Manager – http://www.CoolFlatRoof.com

Second email from Ajay:

Hi Leo,

Thank you so much for your detailed reply. It was most helpful! I’ve had a temporary fix job – a piece of plywood to plug the hole (which their roofer made bigger by cutting away for a closer inspection), then he put some kind of felt??? on top, then he covered the whole lot with some waterproof material(???) and sealed it with tar/bitumen by torch. I’ve attached the photo of the completed work. I’ve also arranged for a professional roofing company to do the permanent fix on Thursday.

If you wish, you may post the conversation on your website to avoid repeat questions and to help others.

Can I ask you another question please related to water leakage through small holes where felt on a flat roof has come away from the main
building wall? Is it best to use lead flashing to seal the felt to the building wall or can some other material be used i.e. the same material
that’s used to fix the actual roof? I was told that if some other material is used, it might start coming away from the wall and leave gaps.

Regards,

Ajay

Image of flat roof repair

 

image of Modified bitumen flat roof repair

 

My second response:

 

Hi Ajay,

As far as roof to wall flashing – you need the roofing material to run up the wall, and then use lead or aluminum counter-flashing. You may also seal the roofing material to the wall, but the counter flashing is the best way. Using both, is preferred – seal to the wall and use counter-flashing.

If you do seal to the wall, I would recommend using roofing grade caulk + water stop (also called water cut-off – a caulk than never cures) and a termination bar with masonry anchors to attach the roofing material to the wall firmly.

There are plenty of pictures on our site if you dig deep enough for you to see how this is typically done.

Good luck, and let me know how it goes, and send some finished pictures. I will post this on one of our sites soon.

Sincerely, Leo.

We will continue to post updates to this flat roof repair, as Ajay sends in the update on how things go, and more pictures. If you have flat roof leaks or roof repair issues that you want to discuss with us and get our help with, send in your questions and pictures. You can post them in the comment section below and we will try to help you out as much as possible.PS – the reason we are posting this email is to helps other homeowners with similar flat roof leak problems and with Ajay’s permission. Because many flat roofs have EPDM Rubber Roofing material installed on them, which often leaks, you can post your rubber roof repair questions on our Rubber Roofing page.

BONUS VIDEO: How To Repair a Tar Flat Roof: