Roofing Shingle Slits for Thermal Expansion Strain Relief
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Solution Overview
Problem
Conventional architectural shingles lack features to accommodate thermal expansion during fires, leading to buckling and creation of tunnels that facilitate air flow and ignition of the roof deck.
Innovation Solution
Incorporating slits in the bottom bituminous sheet of roofing shingles, which allow for strain relief by allowing sections to slide over each other, preventing buckling and maintaining the shingle flush against the roof deck during high-heat conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If architectural shingles are made as continuous laminated sheets, then aesthetic appearance and structural integrity are improved, but fire resistance deteriorates due to thermal expansion causing buckling and tunnel formation
Solution Approach 1:
The continuous bituminous sheet is divided into multiple discrete shingle units with individual tabs and notches. This segmentation allows each shingle to expand and contract independently during thermal events, preventing the buckling and tunnel formation that occurs in continuous laminated sheets, thereby maintaining fire resistance while preserving structural integrity.
Solution Approach 2:
The shingles incorporate tabs with notches at specific locations to create localized flexibility zones. These notches allow controlled movement and strain relief at critical points during thermal expansion, while the rest of the shingle maintains its structural integrity and protective function.
2Shape
If architectural shingles are made as continuous laminated sheets, then aesthetic appearance is improved, but fire resistance deteriorates due to buckling under thermal expansion
Solution Approach 1:
The shingles are designed as segmented units with multiple tabs and notches rather than continuous sheets. This segmentation enables independent thermal movement of each segment, preventing the buckling that compromises fire resistance, while the layered tab structure maintains an aesthetically pleasing appearance.
Solution Approach 2:
The notches and tabs create dynamic zones that allow the shingle to flex and move in response to thermal expansion. This dynamic capability enables the shingle to maintain its aesthetic appearance while accommodating thermal stresses without buckling or forming dangerous tunnels.
3Object-affected harmful factors
If slits are added to the bottom bituminous sheet, then fire resistance is improved by preventing buckling, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process divides the bituminous material into discrete shingle units with tabs and notches before lamination. This segmentation approach, combined with forming slits in the bottom sheet, creates fire-resistant properties through a process that builds upon conventional manufacturing steps rather than adding significant complexity.
Solution Approach 2:
The slits are formed in the bottom bituminous sheet during the manufacturing process, before the sheets are laminated together. This preliminary action integrates the fire-resistant feature into the base material preparation stage, avoiding the need for additional post-manufacturing modifications and reducing overall manufacturing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The slits in the shingles significantly reduce hotspot formation and intensity, enhancing fire resistance and preventing the roof deck from igniting, as demonstrated by ASTM E108 fire resistance tests.
Implementation Method 1
A fire that burns on top of a roof may cause architectural shingles to undergo thermal expansion. This can cause one or more architectural shingles to buckle, pinch, or pucker such that a portion of the shingle pulls away from the roof deck
Implementation Method 2
the slits in the first bituminous sheet that allow for strain relief by allowing sections to slide over each other, preventing buckling and maintaining the shingle flush against the roof deck during high-heat conditions
Data Source
AI summary
One aspect of the disclosure is a shingle including a first bituminous sheet at the bottom surface of the shingle, the first bituminous sheet having a lower edge disposed at the lower end of the shingle, the first bituminous sheet having one or more slits extending from the lower edge of the first bituminous sheet toward the upper end of the shingle; and a second bituminous sheet at least partially laminated to a top surface of the first bituminous sheet, the second bituminous sheet having a lower edge disposed adjacent the lower end of the shingle, the second bituminous sheet having one or more tabs being defined by one or more notches formed in the second bituminous sheet, each notch extending away from the lower edge of the second bituminous sheet.