Fiberglass Roofing - Shingled Roofs Must Be Ventilated Properly

The fiberglass base shingles of today are especially susceptible to heat degradation. Most Roofers do offer a Ridge Vent on every steep sloped roof, regardless of the existing situation. This is done to address a serious concern, but the measures that are being employed everyday usually produce an imbalance in ventilation. Nothing could be more ridiculous and potentially harmful than this approach. The thinking is that hot air rises and it will eventually leave the attic when the roof heats up enough to facilitate the relief of this heat pressure. This is known as thermal buoyancy. The roofers of old used this narrow approach and it used to be adequate several decades ago. Today the mere reliance on thermal buoyancy is no longer adequate and manufacturer warranties are commonly voided because of lack of proper ventilation. Homes have changed and are now tighter than they have ever been. The roofing shingles of today are made up of only one type of asphalt adhered to a stronger, yet more brittle reinforcement.

Fiberglass Based Shingles History

The fiberglass base of the shingle was not organic, would not rot, and did not have to be saturated with a saturant asphalt, as did the old organic paper mat base products. The production plants only needed to apply an adherent asphalt to the mat and attach the granular surfacing and release material and the lighter and purportedly better products were ready for packaging. There was a savings on the amount of asphalt used in manufacture, hence it seemed even a patriotic effort, given the petrochemical and economic climate of the time.

Shortly after the onset of these products, some of the downside of the original design started to show itself in the field. It was a decade of major improvement that followed, compensating and improving in that original product design. Some of the manufacturers touted better seal strips than had ever been seen in the industry. Some of the manufacturers, like Johns Manville, produced such a uniform product that installers were thrilled at the increased ease of production.

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Overlays with Fiberglass Shingles

Over the top installations were affected drastically as installers had to improperly nail (or “nail high”) the product in order to recover roofs without the old roof courses showing (or “telegraphing”) through for a lumpy roof. “High nailing” commonly caused blow-offs on over-the-top installations. The increased heat retention of the overlays gave the fiberglass based products their true field tests. High heat seemed to degrade the fiberglass shingles much faster than their organic, heavier, two step asphalt predecessors. The reasons were two fold. The mat was more brittle and it was common to see roofs crack laterally, as never seen before. The adherent – only, more brittle, thinner shingle was not as malleable, and therefore more susceptible to thermal shock. The process of reformulating the products continued. The asphalt mixes were improved and stricter quality control standards were put into place.

We do not advocate reroof overlays - They do not last - Flashings are ignored - They leak - Please ask your estimator about this.

Laminated Shingles

Again, product “improvements” were made to the original design. The fiberglass mat, asphalt, and seal downs were upgraded. A company named ELK started to produce a much more inexpensive laminated roofing shingle that moved marginally through the northeast market, and seemingly, at the time in the early 1980’s, made no real significant impact on the industry. The manufacturing process used by ELK was several times faster than the major manufacturers' original hand-laminated offerings. The price for the ELK products was significantly less than that of the major manufacturers' products that included the shiplap and double coverage design over critical areas. The big manufacturers, within a decade, had changed over to a similar “In Line Laminate Process,” similar to that originally used by ELK. This process replaced the original hand laminate process and the original ship-lap laminated shingle design disappeared from the roofing marketplace. With it, the uniform look of the laminated roof also was lost. The impact on the laminated roof shingle design is that the butt joints are random and steeper roofs will show the butt joints. This concern leads some people away from the laminated shingles on some jobs. The up side is that the improvements have afforded the manufacturers the ability to rate the warranted life expectancy to double that of the original products on the higher end laminates. These products have become a real value in the asphalt shingle industry. We do caution their use on some high profile and steep roofs, however.

Laminated Shingles on Steep Slopes

The two-piece laminated shingles must be mechanically fastened through the lap of both layers on steep sloped applications. These shingles should also be double nailed on steep slopes. The lap that must be penetrated for proper mechanical fastening is only 5/8” in width. This lap area in the design does not give an adequate holding strength on many steep sloped roofs. Steep roof applications should be scrutinized before consideration of this type of shingle.

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