Reduce Roof Temperatures by as Much as 20 Percent

CertainTeed has strengthened its highly reflective, low-slope CoolStar roofing products with an enhanced ceramic granule surface.

CertainTeed has strengthened its highly reflective, low-slope CoolStar roofing products with an enhanced ceramic granule surface.

CertainTeed has strengthened its highly reflective, low-slope CoolStar roofing products with an enhanced ceramic granule surface. The granulated, uncoated finish is designed to be a cost-effective way to lower commercial building energy consumption and increase occupant comfort. It handles like a standard roofing product without special installation requirements, is more aesthetically pleasing, and yet maintains a high solar reflectivity, reducing roof temperatures as much as 20 percent.

CoolStar products meet ENERGY STAR and California Title 24 requirements. CoolStar also qualifies for LEED points and meets NAHB National Green Building Standards.

CoolStar is designed to work with a wide range of roof systems, including built-up roofing, SBS, APP and self-adhering modified bitumen. It is extremely flexible and durable, because of the layering of high-quality reinforcements, heavy asphalt coating and highly reflective ceramic granules. This toughness combats the negative effects of natural expansion and contraction caused by heating, cooling, light and moisture. In addition, the brilliant white CoolStar surface is factory applied for hassle-free, one-step installation, which helps reduce labor costs.

Creating Visual Impact with Copper and Silver Roofing Membranes

Whether you’re re-roofing a historic building that needs to maintain its aesthetics or you’re working on a new roof construction that has to make a statement, there are many instances in which a building owner would want his or her roof to generate a specific architectural appeal. The most difficult part of this is balancing durability and beauty with cost. Roof systems today have evolved to solve this conundrum. Now, copper and silver synthetic PVC membranes are being used to achieve the desired appearance of a metal standing-seam roof at a fraction of the cost without sacrificing performance.

Alternatives to Metal Roof Systems

Michigan State University replaced the existing slate roof system with SOPREMA SENTINEL Copper Art to provide the desired appearance and required long-term performance.

Michigan State University replaced the existing slate roof system with SOPREMA SENTINEL Copper Art to provide the desired appearance and required long-term performance.


Copper and silver synthetic membranes are great cost-effective alternatives to metal roofs. As flexible synthetic systems, these roof membranes are economical and easy to install by conforming to complex geometries.

Certain synthetic PVC roof membranes on the market today are offered in a variety of colors, some of which can mimic the look of metal roofing. While these roof membranes offer the proven long-term performance of flexible polyvinyl chloride (PVC), they provide the metal appearance via the addition of pigments that can chalk or fade as the pigmented membrane ages, therefore losing the desired aesthetic feature.

Conversely, SOPREMA SENTINEL Copper and Silver Art PVC membranes incorporate copper or aluminum metallic powder into the PVC formulation, producing an enhanced metallic look. Unlike pigmented membranes, SENTINEL Copper Art provides the same weathering capabilities as traditional standing seam copper—the SENTINEL Copper Art will patina as a traditional copper roof would. Silver Art is unique because the color will not fade due to the addition of metallic powder, and its surface layer is factory embedded with an acrylic shield treatment to resist dirt pickup and chalking. Copper Art and Silver Art membranes provide the long-lasting aesthetic appearance and waterproofing abilities of a metal roof.

Applications for Copper and Silver Membranes

Copper and silver roof membranes are often used on buildings where aesthetics are important. Historic buildings, churches, schools, government buildings and army bases are a few examples of where this type of roof membrane has been installed. These buildings may require a particular appearance or designers may simply wish to update the appearance or provide some panache. Mansards or other areas of visible existing light-gauge metal roof systems may be present on these buildings and flexible copper and silver roof membranes may be used as an alternative aesthetic solution.

SENTINEL Silver Art met Glenside Public Library’s leak-free and architectural needs, plus the roofing contractor liked that the SENTINEL membrane was easy to install and looked great upon completion.

SENTINEL Silver Art met Glenside Public Library’s leak-free and architectural needs, plus the roofing contractor liked that the SENTINEL membrane was easy to install and looked great upon completion.

For example, since 2007, the slate roof of the Snyder-Phillips residence hall at Michigan State University had been leaking. The university needed to replace the existing slate roofing system with a new system that would meet the aesthetic requirements of the historic building. SOPREMA SENTINEL Copper Art was installed as a cap sheet to provide the desired appearance and the required long-term performance.

In addition, the Glenside Public Library had an existing standing-seam roof that was tied-in to a low-slope ethylene propylene diene monomer (EPDM) roof. The tie-in between the two materials was problematic and continuously leaked. The library wanted to preserve the standing-seam appearance, but the noise created by wind and rain on the metal roof was a concern.

SOPREMA SENTINEL Silver Art was selected because it could provide the desired look while eliminating the tie-in issues between the steep- and low-slope roofing materials. SENTINEL Silver Art met the library’s leak-free and architectural needs, plus the roofing contractor liked that the SENTINEL membrane was easy to install and looked great upon completion. In addition to its aesthetic appeal, SENTINEL Silver Art also offered the benefit of significant noise reduction when compared to the former metal roof system.

Roofing Technology Advancements

As roofing technology advances, the options for creating a desired aesthetic have evolved. SENTINEL PVC Copper and Silver Art are high-performance roof membranes that provide the appearance of metal with the flexible, long-term performance of PVC, without the weight, expense or complexity of a traditional metal roof.

With Today’s ‘New Age’ Roofs, Removing All System Components May Not Always Be Required or in the Clients’ Best Interest

Years ago, reroofing design involved removing all roof-system components down to the roof deck and rebuilding a new roof system up from there.

PHOTO 1: This EPDM roof’s service has been extended for nine years and counting, approaching 30 years in-situ performance. Here, the restoration of perimeter gravel- stop flashing and lap seams, as well as detailing of roof drains, penetrations and roof curbs, is nearing completion.

PHOTO 1: This EPDM roof’s service has been extended for nine years and counting, approaching 30 years in-situ performance. Here, the restoration of perimeter gravel- stop flashing and lap seams, as well as detailing of roof drains, penetrations and roof curbs, is nearing completion.

Although that is still a viable option and often performed, the coming of age of many single-membrane roofs has altered the method of installing a new reroof system. Options now include EPDM roof restoration; removal of the roof membrane and the addition of new insulation and roof membrane; using the existing roof membrane as a vapor retarder and adding new insulation and roof membrane; removal of the roof cover and installation of new, leaving all the existing insulation in place.

When I first moved into roof-system replacement design some 35 years ago, the dominant roof systems being removed were bituminous, specifically gravel-surfaced asphaltic and coal- tar-pitch built-up roofs. As they aged, their surfaces often started to blister, crack and undulate with ridges—surfaces often unsuitable for roof recover. The bitumen often was deteriorating because of ultraviolet-light exposure; when that occurred, the deterioration of the felts was not far behind. The insulation was mostly perlite or high-density wood fiber; the amount was minimal (low thermal value) and, more often than not, flat or with very minimal slope. Drains were erratically placed, tapered insulation was not often the case and roof edges were predominately gravel stops. In the Midwest, many roof decks were cementitious wood fiber. The roof covers were often patched again and again, even as water infiltrated the system.

PHOTO 2: The re-flashing of roof curbs is an integral part of the restoration of EPDM roof membranes.

PHOTO 2: The re-flashing of roof curbs is an integral part of the restoration of EPDM roof membranes.

When replacement was necessary, the roof-edge sheet metal was removed; the entire existing roof system was removed down to the roof deck; and a new roof system was designed, often incorporating vapor retarders/temporary roofs so the removal of multiple layers of roofing could be accomplished, roof curbs raised, and enhancements of roof drains, curbs and roof edge could occur prior to the installation of the new roof cover. Tapered insulation designs be- came common; this would often require realignment of the roof drains to simplify the tapered design and installation. To accommodate the new insulation thickness, the roof edge had to be raised as did roof curbs, RTU curbs, plumbing vents and roof drains via extensions. Roof membranes changed from bituminous to those classified as “single plies”: EPDM, PVC, CPE, CSPE.

These new roof-system replacement designs resulted in superior roofs—85 percent of all the reroofs I have designed are still in place, still performing, still saving the owner money. Life cycles have moved from eight to 12 years, up to 18 to 25 years and longer. They certainly were more expensive than the original installation and, if a roof designer didn’t have a handle on costs to provide the owner with estimated costs of construction, were often shocking. But these roof systems were good for the client, economy, environment and public.

PHOTO 3: When restoring EPDM roof membranes, the removal of roof penetration flashings and installation of new with target patches will provide another 20 years of watertight protection.

PHOTO 3: When restoring EPDM roof membranes, the removal of roof penetration flashings and installation of new with target patches will provide another 20 years of watertight protection.

Over the years, codes and standards have changed, especially in the past decade, requiring increased insulation values and roof-edge sheet-metal compliance with greater attention to wind-uplift resistance. As the new millennium arrived, these “new age” roofs came of age and owners started to look at their replacement—often with increased costs stifling their budgets.

LEAN THINKING

A factor that increased the performance of many roof systems in the past 20 years was the emergence and growth of the professional roof consultant, often degreed in architecture or engineering, educated in roofing, tested and certified. These professionals brought a scientific approach to roof-system design. Raleigh, N.C.-based RCI Inc. (formerly Roof Consultants Institute) was the conduit for this increased level of knowledge, professionalism and the growth in quality roof-system design and installation.

PHOTO 4: On this roof, the existing loose-laid membrane was removed, open insulation joints filled with spray-foam insulation and new insulation added to meet current code requirements. A new 90-mil EPDM membrane was installed and existing ballast moved onto it to 10-pounds-per-square-foot coverage.

PHOTO 4: On this roof, the existing loose-laid membrane was removed, open insulation joints filled with spray-foam insulation and new insulation added to meet current code requirements. A new 90-mil EPDM membrane was installed and existing ballast moved onto it to 10-pounds-per-square-foot coverage.

As these professionals started to examine the older “new age” roofs, those whose first responsibility was doing what was best for the client saw greater opportunity than just a costly full-roof replacement. Although many roofs today still need to be fully removed, prudent professionals see other opportunities, such as the following:

ROOF RESTORATION
EPDM membrane ages with little change in physical characteristics as opposed to its built-up roofing predecessor; therefore, EPDM membranes often can be “restored” in lieu of removing and replacing the roof. (Studies to support the lack of change in EPDM’s physical characteristics while it ages include Gish, 1992; Trial, 2004; and ERA, 2010.)

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The Roof Cover: The Cap on the Roof System

For nearly two years in this magazine, I have been discussing the various components that make up a roof system: roof deck, substrate boards, vapor/air retarder, insulation and cover boards (see “More from Hutch”, page 3). Although each component delivers its own unique benefit to the system, they are intended to work together. When designing a roofing system, components cannot be evaluated solely on their own and consideration must be taken for a holistic view of the system; all components must work together synergistically for sustainable performance. Unfortunately, I often have seen that when components are not designed to work within the system unintended consequences occur, such as a premature roof system failure. A roof system’s strength is only as good as its weakest link. The roof cover is the last component in the design of a durable, sustainable roof system—defined previously as being of long-term performance, which is the essence of sustainability.

This ballasted 90-mil EPDM roof was designed for 50 years of service life. All the roof-system components were designed to complement each other. The author has designed numerous ballasted EPDM roofs that are still in place providing service.

PHOTO 1: This ballasted 90-mil EPDM roof was designed for 50 years of service life. All the roof-system components
were designed to complement each other. The author has designed numerous ballasted EPDM roofs that are still in place providing service.

The roof cover for this article is defined as the waterproofing membrane outboard of the roof deck and all other roof-system components. It protects the system components from the effects of climate, rooftop use, foot traffic, bird and insect infestation, and animal husbandry. Without it, there is no roof, no protection and no safety. When mankind moved from cave dwellings to the open, the first thing early humans learned to construct was basic roof-cover protection. Thus, roof covers have been in existence since man’s earliest built environment.

WHAT CONSTITUTES AN APPROPRIATE ROOF COVER?

There is no one roof cover that is appropriate for all conditions and climates. It cannot be codified or prescribed, as many are trying to do, and cannot be randomly selected. I, and numerous other consultants, earn a good living investigating roof failures that result from inappropriate roof-cover and system component selection.

There are several criteria for roof-cover selection, such as:

  • Compatibility with selected adhesives and the substrate below.
  • Climate and geographic factors: seacoast, open plains, hills, mountains, snow, ice, hail, rainfall intensity, as well as micro-climates.
  • Compatibility with the effluent coming out of rooftop exhausts.
  • Local building-code requirements, such as R-value, fire and wind requirements.
  • Local contractors knowledgeable and experienced in its installation.
  • Roof use: Will it be just a roof or have some other use, such as supporting daily foot traffic to examine ammonia lines or have fork lifts driven over it?
  • Building geometry: Can the selected roof cover be installed with success or does the building’s configuration work against you?
  • Building occupancy, relative humidity, interior temperature management, building envelope system, interior building pressure management.
  • Building structural systems that support the enclosure.
  • Interfaces with the adjacent building systems.
  • Environmental, energy conservation and related local code/jurisdictional factors.
  • Delivering on the expectations of the building owner: Is it a LEED building? Does he/she want to go above and beyond roof insulation thermal-value requirements to achieve even better energy savings? Is he/she going to sell the building in the near future?

ROOF-COVER TYPES

There are many types of roof-cover options for the designer. Wood, stone, asphalt, tile, metal, reed, thatch, skins, mud and concrete are all roof covers used around the world in steep-slope applications. This article will examine the low-slope materials.

The dominant roof covers in the low-slope roof market are:

    Thermoset: EPDM

  • Roof sheets joined via tape and adhesive
  • Installed: mechanically fastened, fully adhered or ballasted
  • Thermoplastic: TPO or PVC

  • Roof sheets joined via heat welding
  • Installed: mechanically fastened, fully adhered or plate-bonded (often referred to as the “RhinoBond System”)
  • Asphaltic: modified bitumen

  • Installed in hot asphalt, cold adhesive or torch application
  • EPDM (ETHYLENE PROPYLENE DIENE MONOMER)

    Fully adhered EPDM on this high school in the Chicago suburbs is placed over a cover board, which provides a high degree of protection from hail and foot traffic.

    PHOTO 2: Fully adhered EPDM on this high school in the Chicago suburbs is placed over a cover board, which provides a high degree of protection from hail and foot traffic.


    EPDM is produced in three thicknesses— 45, 60 and 90 mil—with and without reinforcing. It can be procured with a fleece backing in traditional black or with a white laminate on top. The lap seams are typically bonded with seam tape and primer.

    EPDM has a 40-year history of performance; I have 30-year-old EPDM roof systems that I have designed that are still in place and still performing. Available in large sheets—up to 50-feet wide and 200-feet long—with factory-applied seam tape, installation can be very efficient. Fleece-back membrane and 90-mil product have superior hail and puncture resistance. Historical concerns with EPDM lap-seam failure revolved around liquid- applied splice adhesive; with seam tape technology this concern is virtually moot. Non-reinforced ballasted and mechanically fastened EPDM roof membrane can be recycled.

    EPDM can be installed as a ballasted, mechanically fastened or fully adhered system (see photos 1, 2 and 3). In my opinion, ballasted systems offer the greatest sustainability and energy-conservation potential. The majority of systems being installed today are fully adhered. Ballast lost its popularity when wind codes raised the concern of ballast coming off the roof in high-wind events. However, Clinton, Ohio-based RICOWI has observed through inspection that ballasted roofs performed well even in hurricane-prone locations when properly designed (see ANSI-SPRI RP4).

    PHOTOS: HUTCHINSON DESIGN GROUP LTD

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Asphalt and Polyurethane Create Membrane

The Garland Co. Inc.’s new OptiMax polyurethane-modified asphalt-based roof membrane combines asphalt with polyurethane to create a durable and long-lasting modified membrane.

The Garland Co. Inc.’s new OptiMax polyurethane-modified asphalt-based roof membrane combines asphalt with polyurethane to create a durable and long-lasting modified membrane.

The Garland Co. Inc.’s new OptiMax polyurethane-modified asphalt-based roof membrane combines asphalt with polyurethane to create a durable and long-lasting modified membrane. OptiMax becomes increasingly resilient as it ages because, with time, polyurethane molecules are chemically linked with one another. The process was first used in Europe in the paving industry. The “active modification” process involves chemically reacting the polyurethane modifier to specific molecules within the asphalt. This modification provides enhanced long-term performance characteristics and weatherability.

GenFlex Roofing’s EZ TPO Peel & Stick Membrane Extends the Installation Window for Contractors to 20 F

GenFlex Roofing Systems has introduced an enhanced self-adhesive technology for its EZ TPO Peel & Stick membrane.

GenFlex Roofing Systems has introduced an enhanced self-adhesive technology for its EZ TPO Peel & Stick membrane.

Indianapolis-based GenFlex Roofing Systems has introduced an enhanced self-adhesive technology for its EZ TPO Peel & Stick membrane. The new adhesive formula offers twice the bonding strength of competitive self-adhesive products (by pound foot per inch in peel testing) and can be installed in temperatures as low as 20 F and as high as 120 F.

The improved Peel & Stick adhesive allows contractors to maximize their productivity. By avoiding separate transportation, mixing, priming and application of adhesive, as well as clean-up of associated rooftop clutter, the self-adhesive membrane means significant time and labor savings. The pre-formulated and factory-applied adhesive also equals uniform performance.

The new EZ TPO Peel & Stick adhesive has no VOCs and is odor-free. By exceeding low-VOC-emissions requirements, the EZ TPO Peel & Stick membrane is safe for installers and building tenants, avoiding any delays or concerns when working in occupied buildings. In addition, the product’s durability and solar reflectance make it an energy-saving option.

PHOTO: Genflex Roofing Systems

Membrane Is Factory Laminated to Cover Board

SOPREMA Inc. has developed SOPRASMART Laminated Boards, which combine SOPRALENE SBS-modified bitumen membrane and cover board into one installation layer, resulting in application consistency and complete adhesion.

SOPREMA Inc. has developed SOPRASMART Laminated Boards, which combine SOPRALENE SBS-modified bitumen membrane and cover board into one installation layer, resulting in application consistency and complete adhesion.

SOPREMA Inc. has developed SOPRASMART Laminated Boards, which combine SOPRALENE SBS-modified bitumen membrane and cover board into one installation layer, resulting in application consistency and complete adhesion. SOPRASMART is manufactured in a controlled setting, utilizing heat-welding equipment to laminate the SBS-modified bitumen coating of the base ply to the desired cover board. This eliminates the risk of delamination or wrinkling, and the sealed overlap protects the assembly from open flame intrusion when torch welding. SOPRASMART is available in a variety of cover-board options, including SOPRABOARD, high-density polyisocyanurate foam board, gypsum panels and high-density rock wool. It can be mechanically fastened or adhered using the DUOTACK adhesive.

SFS intec Receives FM Approvals Certificate for Induction Welding System

SFS intec received an FM Approvals Class 4470 Certificate of Compliance from FM Approvals for isoweld.

SFS intec received an FM Approvals Class 4470 Certificate of Compliance from FM Approvals for its induction welding system, isoweld.

SFS intec, Wyomissing, Pa., has recently received an FM Approvals Class 4470 Certificate of Compliance from FM Approvals, part of FM Global, for isoweld. isoweld is SFS intec’s induction welding system. This certificate approves use of isoweld for attachment of thermoplastic single-ply membranes (PVC and TPO) within roofing systems offered by several single-ply membrane original equipment manufacturers (OEMS).

Seaman Corp. Redesigns Website

Seaman Corp., an innovator and manufacturer of high-performance industrial fabrics since 1949, announces the launch of its newly redesigned corporate website.

“This is part of a major endeavor to improve our engagement with our online audience,” reports Michelle Miller, Seaman Corp.’s marketing manager. “Today, buyers are making the majority of their buying decisions online. Before they ever even talk to a human being, they conduct online research and they poll their social networks for advice. It’s imperative that companies like Seaman Corp. have an excellent online presence.”

To accomplish this, the company partnered with SyncShow, a Cleveland-based digital marketing firm to develop the new site. SyncShow specializes in helping business-to-business clients improve their sales and lead generation strategies through digital marketing.

“We picked SyncShow as a partner because they demonstrated cutting edge digital marketing expertise and because they could prove to us how their efforts drive results for their clients,” reports Kim Seaman, who collaborated on the project as a marketing specialist for Seaman.

The new website is designed to be user friendly, and to attract and engage customers, vendors and potential new hires. But, the overall goal is grander. John Crum, Seaman’s president and COO, defined it. “Seaman Corp. makes excellent products. But when someone buys from us, they get a lot more than a great product,” he says. “They get our people, our culture and they get the knowledge we’ve gained from being in this business for more than 65 years. We wanted to capture all of this and bring it to life with this new site.”

Seaman also hired Frank Greiner, a digital video strategist, to help. Owner of HD Werks, a video production company based in Alliance, Ohio, Frank worked closely with Seaman’s marketing team to create 10 new videos for the site. Each short video showcases something unique about Seaman Corp.’s expertise, its approach to customer care, its products, its customers and the people who work there every day.

The companies will continue their partnership as they work to redevelop three additional sites that showcase Seaman Corp.’s main product lines, including FiberTite Roofing Systems, XR Geomembranes and Shelter-Rite fabrics for architecture. All sites are scheduled to launch yet this year.

Research Helps Industry Organizations Conclude Ballasted Roofs Provide Energy Savings

During the last decade, the roofing industry has been increasingly impacted by two strong forces: first, rising energy prices with no real end in sight, and, second, increasingly stringent building codes and regulations, designed to limit emissions, reduce energy use and mitigate the impact of urban heat islands.

The first definitive study to measure the energy-saving potential of ballasted roofs was done at Oak Ridge National Laboratory, Oak Ridge, Tenn., in 2007.

The first definitive study to measure the energy-saving potential of ballasted roofs was done at Oak Ridge National Laboratory, Oak Ridge, Tenn., in 2007. PHOTO: EPDM Roofing Association

The industry response has also been two-fold: In some instances, new products have been created, such as lower VOC adhesives, primers and sealants, self-adhering membranes and a wider variety of reflective membranes. At the same time, roofing professionals have taken a close look at some of the products that have been in use for a generation. Using rigorous science, they have tested these tried-and-true products to see how they measure up against the new standards. And in many cases, they’ve found that products that have been in use for decades are delivering great results in this new, energy-sensitive environment. Case in point: ballasted roofing, which has been available since the early 1970s, is turning out to be a great choice to meet 21st century needs.

2007 Study

The first definitive study to measure the energy-saving potential of ballasted roofs was done at Oak Ridge National Laboratory, Oak Ridge, Tenn., in 2007. Andre Desjarlais, ORNL’s group leader of Building Envelope Research, and his colleagues had just completed work in which “we had done a fairly substantial comparison of different cool roof technologies, both membrane types, as well as coatings,” Desjarlais says. At the request of EPDM manufacturers, working together at the newly founded EPDM Roofing Association (ERA), Bethesda, Md., as well as manufacturers within Waltham, Mass.-based SPRI, Desjarlais designed and implemented a second study to assess the performance of ballasted roofing. “We undertook a study to effectively expand what we had done earlier on coatings and membranes,” he says.

Other factors also encouraged ORNL to generate data about ballasted roofing. The California Energy Commission, Sacramento, had just revised its codes, essentially defining roofs with high reflectance and high emittance as the only choice of roofing membranes that would deliver high energy savings. Desjarlais believed this definition of a “cool roof” might be inaccurately limiting roofing choice by excluding other roofing materials, such as ballasted roofs, that would deliver comparable savings.

The California Energy Commission, Sacramento, had just revised its codes, essentially defining roofs with high reflectance and high emittance as the only choice of roofing membranes that would deliver high energy savings.

The California Energy Commission, Sacramento, had just revised its codes, essentially defining roofs with high reflectance and high emittance as the only choice of roofing membranes that would deliver high energy savings. PHOTO: EPDM Roofing Association

In addition, in Chicago, a new Chicago Energy Code was adopted as early as 2001 “with high reflectivity and emissivity requirements that limited severely building owners’ and managers’ roof system choices”, according to a paper presented in 2011 by Bill McHugh of the Chicago Roofing Contractors Association. At the roofing industry’s request, a reprieve was granted, giving the industry until 2009 to come up with products with a reflectivity of 0.25.

Faced with that 2009 deadline, the Chicagoland Roofing Council, Chicago Roofing Contractors Association and Rosemont, Ill.-based National Roofing Contractors Association began in 2001 to conduct research on products that would help to meet the city’s goal of creating a workable Urban Heat Island Effect Ordinance while giving building owners a wider choice of roofing products. As part of their effort, the industry coalition turned its attention to the energy-saving qualities of ballasted roofing and coordinated its work with the research at ORNL.

Desjarlais points out the concept of thermal mass having energy benefits has been accepted for years and has been a part of the early version of ASHRAE 90.1. “Thermally massive walls have a lower insulation requirement, so there was industry acceptance of the fact that using mass is a way of saving energy,” he says. “But we had a hard time translating that understanding from a wall to a roof. Whether you do that with a concrete block or a bunch of rocks doesn’t really matter. The metric is no different. Roofs or walls.”

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