Asphalt roof single tab sealant bleed-out staining on a Maryland roof © InspectApedia Bob SissonsAsphalt Shingle Temperatures
Comparison of asphalt shingle manufacturing temperatures vs. on-roof exposure temperatures

  • ASPHALT SHINGLE TEMPERATURES - CONTENTS: what is the range of temperatures to which asphalt roofing products are exposed during manufacture and during service on roofs. Can the difference in these temperature ranges assist in diagnosing apparent or actual asphalt shingle product failures?. Discussion, citations, opinions, diagnosis.
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Temperatures of asphalt shingles: this article describes the different temperatures involved in asphalt roofing product manufacture and compares that to the on-roof temperatures to which asphalt shingles are exposed when in-service. We include the properties of asphalt such as its melting point and flash point, and we describe the properties of asphalt used in the manufacture of roof shingles.

An understanding of the temperatures involved in shingle manufacture and the temperatures that asphalt shingles experience when on a roof can assist in diagnosing actual or apparent roofing product failures, stains, tarry run-out (shown at page top), wind uplift resistant shingle sealant performance, shingle delamination, on-roof repairs or repair attempts and other roofing troubles.

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Asphalt Roof Shingle Temperatures: manufacturing vs. on-roof, diagnostic aids

Asphalt roof single tab sealant bleed-out staining on a Maryland roof © InspectApedia Bob SissonsSaw this on some really heavy duty shingles on a home in the Washington D.C. Metro area. They are bleeding asphalt out. - B.S. (Professional Home Inspector), Maryland, USA. [Details about the roof shingles shown are at ASPHALT SHINGLE TARRY BLEED]

[Click to enlarge any image]

How are Asphalt Shingles Made & What are Shingle Ingredients?

Typical ingredients of an asphalt roof shingle include: Limestone, Oxidized Asphalt (CAS No. 64742-93-4), Mineral Granules, Fiberglass Mat (Fiberglass and Urea Formaldehyde and a Formaldehyde binder), and Backing comprised of sand and talc. In a typical shingle asphalt makes up about 20% of the shingle mass, filler 43%, and the surface granules 25%. - NIST Ret. 7/23/14

During manufacture of asphalt shingles the felt (or fiberglass) substrate is first impregnated with heated saturated asphalt to function as a sealant. This saturated substrate is then coated on both sides with a mineral-filled "coating-grade" asphalt, also heated to high temperature. The shingle's exposure side is then coated with mineral granules that are pressed or rolled into the hot asphalt to bond (most of) them to the shingle surface, and the shingle under-side is also coated with a backing "dust".

An asphaltic sealant material is applied in strips above the shingle's cut-out line or mid-line and serves as a heat-activated sealant that bonds the shingle's under-side to the upper surface of the shingle course below after installation.

Softening Point for Asphalt Used in Roof Shingles

With the caveat that the properties of generic asphalt will not necessarily be identical to the forms in which asphalt is used in shingle manufacture we provide the following data:

The softening point for asphalt (which is does not mean the point at which it liquefies and runs) is 54-173°C or 129.2° - 343.4° F, though when reduced with other solvents the melting point can be reduced. - InChem (ret. 2014).

The temperature range at which asphalt will soften is determined for U.S. purposes by ASTM D-36.

The three types of (air blown) asphalt used in roofing shingles soften at ranges from 140° F to 205° F depending on the grade. - Jones (2006).

Softening Point (not "melting point" nor "liquefying point") of Asphalt Used in Roof Shingles

Roof Shingle Asphalt Type Softening Point
Type 1 140 − 150 °F (60 − 66 °C)
Type 2 166 − 175 °F (74 − 79 °C)
Type 3 190 − 205 °F (88 − 96 °C)

- Source: , The Citizens Compendium, "Asphalt (petroleum), Retrieved 7/22/14, original source

These temperatures explain why dancing about on an asphalt shingle roof on a really hot day may damage it - as roof surface temperatures could certainly be within the lower end of this range.

In sum,

Substances in the asphalt category are semi - solid to solid at ambient temperatures and have negligible vapor pressure s and water solubilities (CONCAWE 2001). - U.S. EPA (2009)

Melting Point or Flow Point for Asphalt (Liquefaction)

But while some sources equate soften with melt, for understanding the properties of asphalt roofing we should distinguish between the softening temperatures (just given) with actual melting-to-low-viscosity-liquid temperatures high enough that asphalt might actually separate from the shingle and run down-roof. I'd call this the liquefaction or flow point.

The boiling point for asphalt is in excess of 300° C or 572° F.- InChem (ret. 2014).

We can see that the manufacturing temperatures of asphalt shingles need to be high enough to permit the asphalt to penetrate the paper or fiberglass substrate, making them likely to be closer to the boiling (say 400-500° F) than the softening point 140° F to 205° F.

Indeed the manufacturers would not enjoy using asphalt at temperatures above 400° C (752° F) since that's its auto-ignition temperature. But it does have to be hot enough to flow into the shingle substrate. (The flash point for slow-curing liquid asphalt is around 150-225° F while an example MSDS for asphalt shingles gives a flash point of greater than 500° F. ) - IKO Production, Inc. (2012)

Similarly, TAMKO® asphalt shingle MSDS information gives the melting point of their asphalt shingles as > 200°F - well above normal on-roof temperatures. - TAMKO Shingle Product (2011)

On-Roof Summer Temperatures for Asphalt Shingles = 10-76°C (about 50° F to 170° F)

Research on shingle durability tests asphalt shingles at temperatures typically up to a maximum of about 170° F - well below the temperatures that occur during manufacture of the product.

In a thoughtfully-designed study, Rose (2006), discussing the role of roof ventilation as a temperature regulator, measured summer time roof temperatures during a study of the effects of a number of variables that affect roof temperatures.

Rose reported that for dark shingles and vented roof construction temperatures were measured between about 10°C and 76°C (about 50° F to 168° F). White shingles were about 23% cooler. In a detail of interest in assessing patterns of roof shingle wear, Rose reorted that for a vented cathedral ceiling construction, research

... shows a very strong sheathing temperature gradient from eaves to the ridge, about 15% colder than the base case at the eaves and 15% hotter than the base case toward the ridge. The thermal pump- ing action that produces such a strong gradient is not difficult to imagine. It becomes appare nt that venting can cool the lower section of a vented cathedral ceiling quite effectively, but the cooling effect is greatly reduced for the upper part of the cavity. - Rose (2006)

Rudd and Lstiburek (1997), studying the contibution of attic venting to temperature control (and arguing for Listiburek's hot roof design) for roofs in Las Vegas, NV USA, reported "tile top" temperatures from about 60F to 130F, and roof sheathing plywood bottom temperatures between 60F and about 125F.

Winandy et als (2004) in reporting on ten years of US FPL study of roof temperatures reported

... The maximum temperatures recorded for the shingles during this period were 68.2°C for black fiberglass shingles, 59.1°C for white fiberglass shingles, 47.1°C [156° F for black and 138° F for white - Ed.]

At ASPHALT SHINGLE INSTALLATION we discuss shingle installation temperatures and at BLISTERS on ASPHALT SHINGLES we discuss shingle manufacturing temperatures as part of the long debate about the blisters found on some new asphalt shingles.

The blister topic convincingly argues that those blisters are a manufacturing artifact - we read research on manufacturing temperatures and the formation of gas blisters that made clear that such temperatures are not reached in-situ on a roof - putting the kebash on claims that blisters formed after installation. Data for that article addresses manufacturing temperature versus subsequent on-roof temperature exposures of asphalt roofing shingles.

It's worth noting that the environmental temperature exposure that asphalt shingles experience on a roof, even in a hot sunny climate, will not approach the temperatures used for manufacturing of the shingle. In short, a roof shingle has been exposed to very high temperatures during manufacture and is cooled, bundled, and packaged for shipment without a constraint on time use - at least not that I have been able to find by research.

So in sum I could not find support for the "need to cure in the yard" argument about asphalt shingles and I would be very grateful if you can send along any citations that are the source of or that support that observation.

Asphalt Roof Shingle Temperatures & Effects in Manufacture & In Situ, Research Citations


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