Ask The Expert Q&A: How Have Commercial Roofing Materials Evolved to Make Reuse and Repurposing Easier?

Sentry Roof has been committed to a sustainable design mindset for decades — it’s what’s best for clients and for the environment. Over time, commercial roofing materials and installation techniques have improved, making it even easier to reuse and repurpose materials efficiently and effectively, which in turn reduces costs even further.

Dave Tidd explains the evolution:

Q: How often do you take reusing and repurposing into consideration when re-roofing?

A: We always consider it because it’s a part of the economics of the project — generally these decisions add value and reduce costs so they’re an important part of decision-making before the re-roofing process begins. We test existing materials in advance so we know how much of it is a viable option for reuse. If materials in the current roof are adequate, then we may have the option to reuse them. Planning to use what’s viable in advance allows us to have the proper amount of new material on hand to manage the re-roofing project successfully and do a turnkey job without having unknown issues with pricing.

Q: How often can you actually reuse or repurpose at least some of the roofing material?

A: About 75% of the time there is at least some adequate material to reuse and perform the proper function with low slope insulated roof systems.

Q: Has there been an evolution in the concept of reuse over time?

A: The concept is basically the same — reuse what can enhance the roof’s performance and reduce costs. I have been working with this approach since 1982, along with most professionals who are involved in evaluating a roofing system design. Most of our added value has been identifying components that are viable to reuse through appropriate testing the materials. The types of roofing materials we use on a daily basis today, however, and how we identify what’s viable have certainly evolved since the 1960s.

Q: How have the materials evolved?

Old way: Applying hot bitumen as part of the roofing system installation process makes it very difficult to reuse the insulation later, even if it has not been compromised by water.

Today’s materials make reusing and repurposing much easier and they allow for significantly more qualified reuse of roofing components. Decades ago most commercial roofing was hot bitumen waterproofing — about 80% of roofs were either hot asphalt or hot coal tar pitch, the latter process is now considered to be carcinogenic.

Most often the hot bitumen roofing material was almost integral with the insulation because of the way the material and the insulation were applied and fully adhered together. Many of today’s materials are often not fully adhered, which means they can be removed separately from the insulation so identifying and using the salvageable insulation is much more likely.

Q: So hot asphalt adhesion on your roof makes reusing the insulation impossible?

A: No, we can still reuse some insulation sometimes. We use infrared thermography or nuclear testing with certain construction, to determine if there’s moisture content in the insulation beneath the roof’s surface, and where that moisture is located — we test section by section. When the tests show there’s a reasonable amount of insulation that can be repurposed, we may have an option to keep it in place as part of the new roof system.

Q: How do today’s roofing materials make it easier to reuse and repurpose?

A: Improvements in both the waterproofing and insulation materials make it easier to apply sustainable design principles. Most of the roofing products in today’s market are single-ply roof materials that are either held down to the building by mechanical attachments or are fully adhered.

When they’re held down mechanically, as they are in a large percentage of single-ply roofing systems, it’s very easy to remove the roofing material without doing any damage to the roof insulation underneath. You can simply detach it and look to see if the insulation can be reused or if it needs to be spot replaced — very easy. So while testing is still important, it’s much easier to do a visual and physical test.

Single-ply materials that have been fully adhered with glue may still allow reuse of good insulation, but the roof membrane is generally not removed to avoid damaging the insulation facers.

New way: Using mechanical attachments for installing roofing insulation, as you see here on a building at the Hartsfield-Jackson Atlanta International Airport, makes it easy to remove and reuse insulation layers when it’s time to re-roof. This method under a mechanically attached single ply membrane essentially allows removing and replacing spot components.

Q: How is insulation different today?

A: It’s different in its composition and its form. In the 1960s the predominant insulations were not focused on R-value, or thermal resistance. The two primary insulation materials were ridged perlite and rigid fiberglass. As the need for better thermal resistance became more apparent, new roof insulations were developed that primarily consisted of isocyanurate foam, called iso for short, that’s molded into boards with a fiberglass facer on both sides.

Compared to perlite and fiberglass, iso has a much higher R-value per inch of thickness, tends to be more physically durable and is somewhat less affected by moisture contamination (although it is still affected but it doesn’t degrade as quickly). The iso board foam is also much more stable with its twin facers, allowing it to be physically picked up and reused in the same board form. Other materials are much more difficult to pick up and put back down. R-value is also a key factor in energy-efficient building performance overall.

Q: Does anyone still use hot asphalt?

A: Yes, some companies are still using it. Sentry Roof still has the equipment but demand is not as great. Most customers prefer the better cost-to-expected-life ratio of newer products and, of course, a greater ability to repurpose portions later. We do continue to use asphalt shingles when the project requires it. Another consideration with both hot asphalt and asphalt shingles is when re-roofing you end up having to send the used materials to landfills even though some asphalt shingles are recyclable. Recycling shingles is expensive and requires a lot of energy, so it’s not as common as it could be.

Q: Are other types of roofing materials recyclable?

Definitely. Some single-ply roofing membranes are recyclable, including TPO and EPDM, and the process isn’t as complex as it is with asphalt. EPDM is the leading recycled commercial roofing product. Some insulation is also recyclable.

There are also circumstances where a material is viable for reuse but not on the same particular project based on the project specifications. This was the case when we were re-roofing a concourse at the Hartsfield-Jackson International Airport. In a situation like that, you can still divert from landfill by contracting with a recycling company who will make the material available for projects with specs that allow the product to be in a used condition.

If it’s time to re-roof your building or if you have questions about how you can reuse the existing materials in your roofing system, or even if you have questions about sustainable design principles in general, please feel free to contact me here at Sentry Roof.

Dave Tidd is Vice President and General Manager for Sentry Roof Services. He is responsible for sales, technical support and general operations management and also project evaluation and design. Dave has been with Sentry since 1995 and worked in roof consulting and inspection for many years before joining Sentry.

To contact Dave, you can call his direct line at 678) 301-5558.