Sprayed Foam Roofing vs Modified Bitumen Torch Down

Pictured below: a modified bitumen roof installation during the 'torch down' process:

Foam Roofing | vs | Modified Bitumen (Summary)

• Expected Roof Life: Lifetime | vs | as long as tar and gravel
  
• Waterproof: Closed cell vs insulation (if added) can soak up water
• Insulation: The Very Best | vs | None (need to add) requires tear-off
• Long Term: Pays for itself in energy savings vs Will end up as land-fill
• Seamless: Monolithic (yes) | vs | torched seams are weak points
• Upkeep: Touch-up with caulk | vs | use care with thin membrane & seams
• Foot Traffic: Thick and hard vs. can be punctured
• Weight: Extremely light | vs | medium weight
• Durability: Can resist hurricane force winds | vs | cannot
• Price: Medium-high | vs | slightly cheaper
• Green: The Greenest | vs | 'Out Gassing' a concern
• Fire Resistant: Very | vs | Not as good as tar and gravel
• Reflective Coating: Yes | vs | May be available at extra cost
• Availablity: Requires Highly Trained Staff | vs | Requires a torch
• Long Term: Pays for itself in energy savings vs Will become landfill

Both foam and modified bitumen torch down roofs are mostly applied to low slope or flat roofs. Many buildings, both commercial and residential fall into this category. For example, in the California Bay Area, Eichler (flat) roofs are very popular, and throughout most of the country, most large warehouses use flat roof systems. When installing a new flat roof or replacing an existing one there are many choices out there. Two of the most popular are modified bitumen and foam roofing. Both of these systems are based on drastically different technologies, and both give drastically different results as well. This article is a point by point comparison to help you understand some of the key differences between modified bitumen roofs vs foam roofing.

A Spray Foam roof installation in progress. Foam roofs provide a seamless, insulated monolithic barrier, which can last the life of the building:

Expected Roof Life

First, foam roofing will last the lifetime of the building (with a qualified, experienced application team), while modified bitumen will maybe last 40 years (at best, with bi-annual upkeep, and flashing replacement at year 20).

Seams, Insulation

SPF Foam Roofing has R-Values ranging from 4 to 6 and up, and the roof creates a seamless monolithic barrier, which blocks moisture and air movement. And, especially at extreme temperatures, foam outperforms traditional forms of insulation. Most foam roof systems are installed at a depth of 1” to 2”, which represents more insulation value than 4” to 8” of fiberglass. Mod bit roofs have torched seams (i.e. not seamless). Adding fiberglass insulation may require the existing roof substrate to be torn off. Even 4” of fiberglass on a mod bit roof will be less effective than 1” of foam. Homes with SPF foam roof systems generally save between 50% and 80% on their monthly heating and cooling bills after an installation is completed (foam vs BUR, or other black asphalt based roofing).

Self Adhering

Sprayed Foam Roofs are self-adhering and require no attachment to the roof substrate. Modified bitumen roofs must be adhered to the roof surface with sealants such as hot tar, or tape. Spray Foam Roofs are extremely resilient to uplift, and have been demonstrated to adhere to roof substrates even during hurricanes and gale force winds.

Correct Low Areas and Ponding

One of the greatest benefits of foam is that low areas can be correct where a roof is slumping or slightly caving in. Polyurethane Sprayed Foam can be sprayed to correct low areas. Ponding is simply a low area where a roof is sagging. After rainfall, water collects in these areas, and after long periods of time, the water often seeps through BUR, EPDM, or other roofing materials through any weakness in the seams. A professional SPF applicator can build up & even out these low areas with SPF foam.

Waterproof, closed cell foam is used to build up the low area of a roof:


The result is a flat (no longer sagging) area that will no longer retain water:


Foam is extremely lightweight and durable, so adding 1-2" in a low area (as needed) will have negligible impact on the weight of the roof. A good SPF crew will make sure an area with a history of ponding is completely dry before installation. As needed, a blow torch or other device may be used to remove any excess moisture before foam is sprayed. As needed, the underlying roof should be inspected before the foam is sprayed. Dry rot, or damaged / weakened roof boards must sometimes be replaced with fresh ones. This is more the exception than the rule; however care must be taken because although this is a simple task before spraying the foam, this can become monumental work after a spray foam installation is complete.

Reflective Coatings

Most SPF applicators use energy star approved reflective coatings (if they don’t, ask for it). This counteracts the urban heat island effect by preventing the roof from absorbing heat. Most torch down roofs are black or very dark after installation, which means the roof will absorb the heat of the sun. Such roofs have been testing during 90 to 100 degree Fahrenheit weather, and it has been determined bitumen based roofs may easily reach temperatures upwards of 150 degrees Fahrenheit! The collective presence of large numbers of black asphalt streets, and black asphalt roofs has contributed to what is now called the urban heat island effect, effectively raising the outside temperature in cities and surrounding areas by as much as 10 degrees Fahrenheit. Depending on insulation (or lack of), the interior of a home with a black asphalt roof may be substantially hotter than a roof with a reflective coating. Reflective coatings counteract the urban heat island effect, and keep your home cooler.

A completed foam roof installed with energy star compliant reflective coating:

Geographical Limitations For Foam Roofing

If you're in Alaska or another place where foam can't be sprayed 300 or more days of the year, you might not have a choice in the matter. Foam requires low humidity and temperatures of 80 to 100 degrees Fahrenheit are ideal. Foam can be sprayed in slightly higher or lower temperatures, but the applicator must be vary cautious or the roof will have an unusually lumpy or ugly ridged look. If you're in California, Texas, Arizona, Florida, or another temperate place, there's plenty of qualified contractors that can do the work. There are no such limitations for modified bitumen roofs.

Pictured below: a modified bitumen roof installation in-progress.

Note: each modified bitumen seam must be sealed; compare to foam which installs as a single seamless barrier.

Michelson Technologies 30 Year Study

A thirty year scientific life cycle cost analysis of SPF roofing systems was performed by an independent third party with conclusive results. SPF roofing systems, in most situations had a lower 30 year life cycle cost than membrane roof systems. The study was conducted with ASTM E-917 building life cycle standards. The actual dollars saved ranged from 13% to 56% based on re-coat frequency. The cost savings correlated to a recoat schedule of 6 years (13%) to 15 years (56%). An important note: it is best to have a foam roof inspected and recoated at the five year mark to prevent any long term issues from occurring. Then recoating every 10-15 years as needed makes sense.

Summary

Sprayed Foam Roof is superior Modified Bitumen Torch Down on every measure except price. Generally, a foam roof will cost a little bit more. This is because the materials and equipment required are more expensive, higher quality, and more technologically advanced. A Sprayed Foam Roof (SPF Roof) will eventually pay for itself because it will last the life of the building, and because of the improved roof insulation in most cases, energy costs such as heating, cooling, etc are cut by 50% to 80% (depending on factors, such as existing roof insulation, double pane widows, etc). Even the highest quality modified bitumen roof will need flashing replaced in 20 years, and most likely, a complete roof replacement at 40 years. Also consider, if you have an older roof with a history of ponding, or structural sagging, an SPF foam roof system may be the only one that does not end up leaking.

After you decide which roof system should be installed, you’ll still need to get bids and decide on a contractor. Here’s a few tips on selecting a qualified roofing specialist.

Identifying Quality Contractors

Only a properly trained Foam Roofing contractor will be capable of installing an SPF roof system that will last the life of your building. It's critical to pick a highly qualified SPF contractor for any foam roofing related work. There are critical mistakes that can be made by inexperienced contractors which may lead to disastrous results. The best way to find high quality local contractors is through services such as diamond certified, value star, eichler network, or other third party rating services. For example, Dura-Foam Solar Center Inc, located in the California, Bay Area is the leading local contractor with over 10,000 local installations over the past three decades. Dura-Foam has roofs which are now 30+ years old, and still in great condition.

Energy Star, Diamond Certified, Valuestar, and BBB logos:


If the Foam Roofing company has done quality work in the past, and has been around a while with no complaints, and you're in a climate that allows foam (actually, you probably wont find a local foam roofing contractor if your weather doesn't allow it). Anyway, given all those assumptions, Foam is clearly the best choice. Once again though, your local clime might not allow for the spraying of SPF foam, or you might not have good local contractors.

If you decide to install a modified bitumen torch down roof system, you should probably do the same background checks you would for a foam roofing company. Check their license number again the state license board online service. Also, check the better business bureau and any local ratings services to confirm the contractor has been around at least a little while, and has done quality work with both older and newer customers.

Critical Success Factors For Lifetime Spray Foam Roofing Installation

Thanks for the great post. I agree, for anyone informed that knows how to properly select a qualified contractor, foam roofing is hands down the best choice. In some areas it may be hard to find a good SPF contractor, but I think one of the easiest ways to find a good contractor, is to choose someone who has been in business at least 10 years and has no outstanding complaints with the BBB and who both old & new customers are still willing to recommend. An experienced contractor can install a foam roof that will last the life of your building (40 years or more), with recoats at year 5 and year 15.

Your estimator might be well educated; but the most important person is the team lead for the actual application of the foam roof.

Picture: Foam roof systems are self-adhering when properly installed (during warm, dry weather). A proper foam roof installation is extremely durable and uplift is nearly impossible. The roof on the left is an SPF sprayed foam roof, and the roof on the right is a modified bitumen roof. Both were hit by hurricane hugo. The mod bit roof took extensive damage, while the foam roof is completely intact.


Make sure (if you are installing over an existing substrate) that the following steps are properly completed:
1-clean old substrate, secure old substrate with nails or staples
this means all old dirt, gravel, or loose roofing material is completely removed. Large areas of exposed roof need to be covered with material such as rolled roofing and securely fastened with staples or another type of fastener. The actual foam roof needs no fastening, but the substrate MUST be completely dry & completely clean, or the foam will not adhere. If the substrate is wood (e.g. new construction), the roof must be covered with some type of single ply material (such as rolled roofing), otherwise, the roof may look bumpy or uneven, or foam could spray through ceiling boards into a home (e.g. on an Eichler with no insulation). No roof installation is need with a foam roof install--a single inch of foam is more effective than 4" of fiberglass.

2-drains, flashing
make sure that your foam installer replaces any worn out flashing with new flashing, and make sure drains are COMPLETELY cleaned out (and replaced if they are worn or old). This means, any loose gravel, rocks, or leaves/ branches--anything which could block your drain is completely removed. I have seen roofs leak because a drain gets backed up and water seeps from a clogged drain into a sidewall, or overhang into a home. The #1 cause of roof leakage on a properly installed foam roof is a clogged drain. If the drains & flashing are in excellent condition there's no need to replace them.

3-AC units, Skylights, Pipes, Vents, Chimneys
A foam roof must be vented properly, or trapped air can create eventually create uplift over many years. Generally, skylights must be raised, and old vents replaced to prevent leaks. Some pipes may require flashing at roof entry points to assure no leaks are possible. Large AC roof units should be placed up on blocks (generally wood covered with metal or other material), so that the application team can spray underneath. Chimneys sometimes need special care to prevent leaks, such as flashing around the base (before it the foam is sprayed over).

A good foam installation crew will go back over their work, after the foam is complete (and before spraying the base coat), cut out drains, or cut the edges of the (by the flashing) as needed to assure water can properly drain from the roof. Where the foam is cut extremely low, or almost completely removed, sealant should be used (e.g. if channels were cut in the foam to assist in drainage).

4-Other 3rd party contractors
Generally, it's best to make any plumbing, electrical, solar, or other contractors do their work first, and let the SPF installation crew finish. You don't want any contractors unfamiliar with SPF roofing systems to damage an existing roof or make other mistakes which can cause leaks. I've seen plumbing, AC, electrical or other types of contractors damage SPF roofs, forcing customers to call back the SPF roofing company to come fix the newly created problems.

Find a local Foam Roofing contractor.

Thanks for your post.I always consider Foam Roofing is best.

That was a lengthy and informative discussion about the comparison of foam roofing vs modified bitumen torch down. All in all, I understand that foam roofing is always better in the long run. And also, I can see that most buildings are actually using foam roofing so it only says that more are trusting it.

I think foam roofing is sometimes ignored because people assume since a building came with a torch down or modified bitumen roof, that perhaps that's the best replacement roof. The more educated a person is on roofing, the more likely they will make the best choice. In terms of flat roofing, generally the more a person knows, the more they are likely to choose a foam roof system.