WESTERN ROOFING – JANUARY/FEBRUARY 200554

Review of Residential Roofing Materials, Part IA Review of Methods for the Manufacture of Residential Roofing Materialsby Hashem Akbari, Ronnen Levinson, and Paul Berdahl, Heat Island Group, Lawrence Berkeley National Laboratory

ccording to Western RoofingInsulation and Siding maga-zine (2002), the total value

of the 2002, residential roofing mar-ket in 14 western U.S. states (Alaska,Ariz., Calif., Colo., Hawaii, Idaho,Montana, Nevada, New Mexico, Ore-gon, Texas, Utah, Wash., andWyoming) was about $3.6 billion.We estimate that 40% ($1.4 billion) ofthat amount was spent in California.The lion’s share of residential roofingexpenditure was for fiberglass shin-gle, which accounted for $1.7 billion,or 47% of sales. Concrete and clayroof tile made up $0.95 billion (27%),while wood, metal, and slate roofingcollectively represented another $0.55billion (15%). The value of all otherroofing projects was about $0.41 bil-lion (11%).

We estimated roofing area marketshares by assuming that roofing pro-jects involving concrete tile, clay tile,wood shingle/shake, or slate were50% to 100% more expensive thanthose using other roofing materials,such as shingle, metal, or membrane.This suggests that the roofing marketarea distribution is 54-58% fiberglassshingle, 8-10% concrete tile, 8-10%clay tile, 7% metal, 3% wood shake,and 3% slate.

The functional distribution of thesteep-slope roofing market (includingboth residential and small-commer-cial buildings) was about 60%replacement, 25% new construction,and 15% repair and maintenance.

This paper examines methods formanufacturing fiberglass shingles,concrete tiles, clay tiles, and metalroofing that constitute over 80% of allroofing materials, by both expendi-ture and area. We have focused onthese four roofing products becausethey are typically colored with pig-mented coatings or additives. We donot discuss production of wood and

slate roofing. A better understandingof the current practices for manufac-turing colored roofing materialswould allow us to develop cool col-ored materials creatively and moreeffectively. The paper also discussesinnovative methods for increasing thesolar reflectance of these roofingmaterials.

MethodologyWe reviewed the pertinent litera-

ture for production of roofing materi-als and visited several roofing materi-al manufacturing plants.

Literature ReviewThe following briefly summarizes

several pertinent sources of informa-tion about roofing manufacturingmethods available from websites,articles, papers, patents, and books.In The Science and Technology of Tradi-tional and Modern Roofing Systems,Laaly (1992) provides an overview ofthe production and application ofvarious roofing materials. A websiteof the National Park Services (NPS2003) also provides the historicalbackgrounds of several roofing mate-rials, including asbestos-cement shin-gle, asphalt shingle, clay tile, compo-sition (built-up roofing), metal, slate,and wood shingle.

The Department of Health andHuman Services (DHHS 2001) andthe Environmental Protection Agency

2002 Project residential roofing market in the U.S. western regiona surveyed byWestern Roofing (2002).Roofing Type Market share by $ Market share by roofing area (%)

$B % Estimate 1 Estimate 2Fiberglass Shingle 1.70 47.2 53.6 57.5Concrete Tile 0.50 13.8 10.4 8.4Clay Tile 0.45 12.6 9.5 7.7Wood Shingle/Shake 0.17 4.7 3.6 2.9Metal/Architectural 0.21 5.9 6.7 7.2Slate 0.17 4.7 3.6 2.9Other 0.13 3.6 4.1 4.4SBC Modified 0.08 2.1 2.4 2.6APP Modified 0.07 1.9 2.2 2.3Metal/Structural 0.07 1.9 2.2 2.3Cementitious 0.04 1.1 1.2 1.3Organic Shingles 0.02 0.5 0.6 0.6Total 3.6 100 100 100a. The 14 states included in the U.S. western region are Alaska, Ariz., Calif., Colo., Hawaii, Idaho, Montana,Nevada, New Mexico, Oregon, Texas, Utah, Wash., and Wyoming.

INSPECTING THE FINISHED PRODUCT AT A CLAY TILE PLANT.

WESTERN ROOFING – JANUARY/FEBRUARY 2005 55

(EPA 1995) have each preparedextensive documents discussing vari-ous manufacturing methods forasphalt roofing products. Thesefocus on environmental pollution,and do not address the effects of roofreflectivity and its effects on heating-and-cooling energy use and on roofdurability.

Brown (1960) and Jewett et al.(1994) detail the manufacture of col-ored roofing granules in chapters of1960 and 1994 editions of IndustrialMineral and Rocks. Though these textscover a wide range of technical andmarketing issues related to the manu-facture and production of coloredgranules, they provide limited infor-mation on granule coloring tech-niques. Joedicke (1997 and 2002) dis-cusses this topic in greater detail.

Finally, Paris and Chusid (1997,1999) briefly describe methods forcoloring concrete products usingpowder, liquid, and granulated pig-ments. They also discuss issues relat-ed to the durability of colored con-crete.

Plant VisitsWe visited a shingle plant, a metal

roofing plant, and a clay tile plant insouthern California; and a granuleproduction plant and a concrete tileplant in northern California.

Asphalt Shingle: Asphalt is adark-brown-to-black cementitiousmaterial, solid or semisolid, in whichthe predominant constituents are nat-urally-occurring or petroleum-derived bitumens. It is used as aweatherproofing agent. The termasphalt shingle is generically used forboth fiberglass and organic shingles.There are two grades of asphalt shin-gles: (1) standard, a.k.a. 3-tab; and (2)architectural, a.k.a. laminated or

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CLAY TILES ARE KILN FIRED.

ing process. Concrete tiles are eitherair-cured or auto-claved. Color isadded to the surface of the tile with aslurry coating process, or added tothe mixture during the manufactur-ing process.

Clay tile is a combination of vari-ous clays and water. Color is addedto the surface of the tile with a slurrycoating process before the tile is kiln-fired.

Metal: Metal roofs can be classi-fied as architectural or structural.

Examples: Architectural (hydroki-netic-watershedding) standing-seamroof systems are typically used onsteep slopes with relatively shortpanel lengths. They usually do not

have sealant in the seam because theyare designed to shed water rapidly.They do not provide structural capac-ity or load resistance, and their instal-lation is less labor-intensive becausethey have a solid substrate platformthat makes installation easier..

Structural (hydrostatic-watershed-ding) standing-seam roof systems areversatile metal panel systems that canbe used on both steep- and low-sloperoofs and are designed to be water-resistant. Most structural standing-seam systems include a factory-applied sealant in the standing seamsto help ensure water tightness. Thesepanel systems provide structuralcapacity and load resistance.

Manufacturing Methods - ShinglesProduction of colored granules.

Granules cover over 97% of the sur-face of a typical asphalt-soaked fiber-glass shingle. Granules are appliedto asphalt shingles for several rea-sons, including UV protection, col-

WESTERN ROOFING – JANUARY/FEBRUARY 200556

dimensional. Asphalt shingles comein various colors.

Examples: Fiberglass shingles,commonly known as “asphalt shin-gles,” consist of fiber mats that arecoated with asphalt and then coveredwith granules. Granules, a.k.a. min-eral granules or ceramic granules, areopaque naturally- or synthetically-colored aggregates commonly used tosurface-cap sheets and shingles.

Review of Residential Roofing Material, Part IOrganic shingles have a thick cel-

lulose base that is saturated in softasphalt. This saturation makes themheavier than fiberglass shingles, andless resistant to heat and humidity,but more durable in freezing condi-tions.

Tile: Usually made of concrete orclay. Concrete tile is a combination ofsand, cement, and water; the waterfraction depends on the manufactur-

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FIBERGLASS ENTERING THESHINGLE PRODUCTION MACHINERY.

dust and to improve asphalt adhe-sion. The mineral oil typically evapo-rates within a few months.

The pigments used for coloredgranules must have certain proper-ties, including stability at high tem-perature, chemical inertness, ease ofdispersion, color consistency, weath-er stability, non-toxicity, and lowcost. Common pigments used inroofing granules include titaniumdioxide (white), zinc ferrite (yellow),red iron oxides, carbon black, chromeoxide (green), and ultramarine (blue).

WESTERN ROOFING – JANUARY/FEBRUARY 2005 57

oration, ballasting, impact resistance,and fire resistance.

Granule manufacturing plants aretypically sited near a quarry of suit-able base rocks, including andesite,coal slag, diabase, metabasalt, nepha-line syenite, quartzite, rhyodacite,rhyolite, and/or river gravel. Theessential characteristics of the baserock include: opacity to ultravioletlight, to protect the asphalt fromultraviolet damage; chemical andphysical inertness, to provide resis-tance to acid rain, leaching,freeze/thaw, wet/dry cycling, oxida-tion and rusting; low porosity, toimprove physical strength, bindingbetween coating and rock, and effi-ciency with which the pigment coat-ing covers the surface; and resistanceto high firing temperatures. Othernecessary characteristics includemoderate hardness, to remain intactduring the granule coloring process;moderate density (to weight the shin-gle against wind lift); uniformity, andcrush equidimensionality (to preventdirectional embedment in the shinglemanufacturing process, whichchanges shingle appearance).

In a roofing-granule manufactur-ing plant, rocks blasted from quarriesare crushed in several stages toreduce the rock to granule-size aggre-gate (0.5 to 2 mm). In this process,the larger aggregates are recycled tothe crushing system and the smallerdebris is separated for other usage.

Once the granules are milled to theright size, they are transferred to thecoloring plant. In the coloring plant,in a continuous process they aremixed with a semi-ceramic color coat-ing. The coating is a mix of color pig-ments in a sodium silicate, hydratedkaolin clay, and water. The preheat-ed granules are mixed and tumbledwith coating sufficient to cover thesurface. The wet coated granules arethen transferred to a rotary kilnwhere they are gradually heated to250-550°C (500-1,000°F). This dehy-drates and polymerizes the coating,forming an insoluble pigmentedceramic layer. The granule is thengradually cooled in a rotary cooler bysprayed water and circulated air.Finally, the pigmented granules arecoated with mineral oil to control

Typically, 2.3-2.7 kg (5-6 lb.) of pig-ment per ton of granules are requiredto create a single-layer coating. Mul-tiple coatings are needed to increasepigment loading. Some granule man-ufacturing plants have parallel color-ing lines that can be used in series toapply multiple layers of coatings ongranules. The granules (both coloredand uncolored) are transported toshingle manufacturing companies byroad and rail.

(Editor’s Note: Next issue, we’ll pre-sent Part II of this article.)

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