IECC climate zones
The zone map and its A/B/C moisture designations, and why a zone predicts assembly requirements better than a state line does.
Climate hazards
Climate does not damage roofs. Specific hazards do.
“Harsh weather” explains nothing. Hail, uplift, ember intrusion, freeze-thaw, vapor drive, and salt each attack a different part of the assembly and each has a different answer.
30-second answer
What actually determines how a roof performs in my climate?
The specific hazards your location exposes it to, and how the whole assembly is detailed against them. A covering rated for one hazard can be irrelevant to another. Most US buildings face two or three of the hazards below, and the roof should be specified against those rather than against the weather in general.
Published guides
The ten hazards, and what each one does.
Each page explains the mechanism, what genuinely mitigates it, and the limits of what a roof can be asked to do.
Hurricane exposure
Why most interior water damage does not require the covering to blow off, and why a sealed deck matters more than a headline wind number.
Tornado and straight-line wind
No roof survives a violent tornado core. What attachment and edge metal genuinely change is performance in the far more common straight-line wind.
Hail exposure
What the impact tests actually measure, why “Class 4” is not “hail proof,” and how functional and cosmetic damage differ.
Wildfire and WUI exposure
Embers, not flame fronts, destroy most structures. Vents, eaves, and debris matter more than the covering — and Class A is an assembly rating.
Heavy snow and ice
Drifting and unbalanced load rather than average depth, sliding snow, and where ice-barrier requirements genuinely come from.
Freeze-thaw
Water absorption, not hardness, decides which tile and slate survive. Why a climate hovering around freezing is harsher than one that stays frozen.
Extreme heat and UV
Heat does not fail a roof in one event; it ages it continuously. Where cool roofing pays, and where it costs heating energy instead.
High humidity and moisture
Vapor drive reverses by climate and season, so an assembly detailed for a cold climate can condense moisture inside itself in a hot-humid one.
Coastal salt and corrosion
Coastal metal roofs usually fail at the fasteners and flashings, not the panels. Distance from surf is the governing variable.
Seismic exposure
Seismic force scales with mass, and the roof is the highest mass in most buildings — which makes a heavier covering a structural question.
Coverage map
Climate zones and regional guidance.
Hazards explain the mechanism; zones and regions explain which ones apply where you are. Nothing in this list is published yet.
Zone-by-zone guidance
One page per zone, from hot-humid Zone 1 to subarctic Zone 8: dominant hazards, assembly implications, and common local practice.
Northeast
Deep snow and ice, freeze-thaw, older housing stock, slate and wood tradition, dense historic districts.
Mid-Atlantic
Mixed-humid transition, rowhouse low-slope additions, storm remnants, and wide permitting variation.
Southeast
Coastal hurricane wind and product-approval regimes; inland heat, humidity, and severe thunderstorm hail.
Midwest and Great Plains
Four-season extremes, the highest hail frequency in the country, derechos, and freeze-thaw.
Mountain West
Snow load and elevation, intense UV, wildfire WUI exposure, and ice damming at altitude.
Southwest desert
Extreme heat and UV, low-slope prevalence, monsoon burst rainfall, and the tile tradition.
Pacific West
Wet-season rain volume, marine exposure, wildfire WUI, seismic demand, and the Pacific Northwest moisture regime.
Next step
Make your hazards part of the scope.
A quote that does not mention your dominant hazard has not been written for your building. The checklist turns that into a question an installer has to answer.
Preview the buying kit