Questions covered in this guide
Read the test name with the number
IBHS describes multiple roof wind tests and explains that airflow speeds in a shingle fan test are not wind loads. Comparing two large wind numbers without their test methods can therefore conceal important differences.
Request the project-specific explanation
Ask the roofer to identify the product, test standard, and supporting document behind each wind-related statement in the proposal. Then ask who determines the assembly appropriate for the property and where that decision is recorded. Keep local design requirements, product testing, and warranty language as separate subjects. A marketing number should not replace the installer’s explanation of how the actual deck, attachment, edges, and accessories fit the proposed system.
Create a three-part evidence sheet
Make sections headed product testing, property design, and warranty terms. Under testing, record the named standard and document. Under property design, record the responsible professional and the specific assembly reference they provide. Under warranty, record the exact document and unanswered conditions. If a bidder puts the same number in all three sections, ask for clarification instead of assuming the three claims mean the same thing. Keep the reply with the proposal.
Compare the scope behind the rating
Ask whether an alternate product changes attachment or accessory requirements and have the contractor document any resulting scope change. Save the final specification for later repair work. No test label means a home is immune to future storm damage, and this guide does not calculate site wind loads. The national roofing calculator supports preliminary cost planning only. A useful decision rests on the documented assembly and a clear answer about who is responsible for its design.
Putting it into practice
The guide separates laboratory tests, property design, and warranty conditions. That structure gives homeowners a way to question large wind numbers without attempting engineering calculations or treating different test methods as interchangeable.
Sources and supported claims
IBHS describes different wind test methods for asphalt shingles and metal roof assemblies.
Source ↗ · national · Checked 2026-10-12
IBHS explains that wind speeds in one shingle fan test are airflow over the roof, not wind loads.
Source ↗ · national · Checked 2026-10-12