Aluminum Windows for Extreme Weather: 5 Critical Climate Specs

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Part of the Aluminum Window Specification Guide

Related: Thermal Break Aluminum Windows · What Drawings to Send to an Aluminum Window Manufacturer

Choosing aluminum windows for extreme weather is not simply a matter of selecting a stronger frame. The correct specification depends on what the climate is actually trying to do to the building.

Hot climates increase solar heat gain. Cold climates increase conductive heat loss and condensation risk. Coastal environments increase corrosion exposure. High-wind regions increase structural and water-penetration demands.

The mistake is assigning one universal number to each climate. A better engineering approach is to identify the dominant environmental load, select the relevant performance parameter, and then verify that parameter with project-specific documentation.

For Canadian projects in particular, the applicable provincial or territorial code should be checked first. The 2025 National Building Code of Canada and National Energy Code of Canada for Buildings provide the current national model-code framework, but jurisdictions determine which provisions are adopted locally.

Quick Specification Summary

The important distinction is this:

Climate determines the performance priorities. The project determines the final numbers.

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Why One Aluminum Window Specification Does Not Fit Every Climate

Aluminum is not inherently a “hot climate” or “cold climate” material.

Its performance depends heavily on the system design: thermal break, profile geometry, glazing, seals, finish, hardware, drainage and tested configuration.

For example, a thermally broken aluminum window can be designed for cold conditions, while a high-performance solar-control IGU can be paired with the same general frame concept for a hot climate.

Similarly, a coastal project may require a more carefully specified finish and corrosion-resistant hardware, while a high-wind project may require a specific design pressure and tested assembly.

This is why aluminum window specification by climate should start with exposure conditions rather than catalogue descriptions.

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The 5 Climate Priorities for Extreme-Weather Windows

1. Hot and Desert Climates: Control Solar Heat Gain

For hot climates, the dominant issue is often solar heat gain rather than simply conductive heat transfer.

The important parameters include:

• SHGC
• whole-window U-value
• glass visible transmittance
• Low-E coating type
• external shading
• window-to-wall ratio
• facade orientation

A low-SHGC glazing package can reduce solar heat entering the building, but there is no universal “best” SHGC.

A heavily shaded north-facing facade may require a different glass specification from an unshaded west-facing facade.

Canada’s NECB user guidance specifically notes that SHGC selection affects heating and cooling loads and should be considered alongside location, orientation and exterior shading.

Procurement rule: do not specify only “Low-E glass.” Request the actual glass make-up, SHGC and thermal data for the proposed IGU.

For large glazed facades, also review the aluminum frame’s thermal-break design rather than evaluating the glass alone.

For projects where the glazing specification is not yet fixed, Starveil’s aluminum window glass specification guide provides a useful framework for comparing Low-E, cavity, argon, spacer and whole-window performance.

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2. Cold Climates: Specify the Whole Window, Not Just the Glass

Cold climates shift the priority toward heat loss and interior surface temperature.

The critical parameter is the whole-window U-value, not simply the centre-of-glass Ug.

A cold-climate aluminum window may combine:

• thermally broken aluminum framing
• Low-E insulating glass
• argon-filled cavity where appropriate
• warm-edge spacer
• optimized frame geometry
• controlled air leakage
• appropriate installation detailing

The important correction is that there is no universal Uw value that defines every cold-climate window.

A target such as 1.8 W/m²·K may be useful as an example in some specifications, but it should not be presented as the Canadian requirement for all cold regions.

Canada’s 2025 model codes have introduced updated energy-efficiency provisions and projected climatic data, but the requirements applied to an actual project depend on the adopted jurisdiction and compliance path.

Procurement rule: request the complete Uw for the actual window size and configuration, rather than comparing one supplier’s Ug with another supplier’s Uw.

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3. Coastal Climates: Specify the Finish and Corrosion System

Coastal exposure creates a different problem: salt-laden moisture, UV exposure and corrosion risk.

The finish specification should therefore be treated as an engineering requirement, not simply a colour selection.

For North American projects, AAMA 2605 is a high-performance organic-coating specification for architectural aluminum. The current FGIA listing shows AAMA 2605-26 as active. Its testing framework addresses properties including weathering and corrosion resistance.

The commonly cited 4,000-hour salt-spray figure should also be described correctly: it is a laboratory test requirement within the AAMA performance framework, not a promise that a window will survive exactly a certain number of years beside the ocean.

For anodized aluminum, the specification should identify the applicable anodizing standard and coating thickness. AA25 is commonly used for severe/aggressive exterior exposure, but the appropriate grade should be selected according to the actual environment and project specification rather than treated as a universal coastal requirement.

The current North American reference for anodized architectural aluminum is AAMA 611-26.

Also check:

Important: the coating standard applies to the finish system. It does not automatically certify the entire window assembly.

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4. High-Wind and Hurricane Regions: Start With Design Pressure

High-wind projects should not be specified simply as “hurricane windows” or “high-wind aluminum windows.”

The starting point is the project design wind pressure.

That pressure is affected by factors such as:

• geographic location
• building height
• exposure
• building geometry
• opening location
• positive and negative pressure
• surrounding terrain
• applicable building code

ASTM E330/E330M provides a laboratory method for evaluating structural performance under uniform static air-pressure differences. ASTM also explicitly notes that wind loading in real buildings depends on factors such as direction, height, building shape and terrain.

For Canada and the broader North American market, NAFS is particularly important. AAMA/WDMA/CSA 101/I.S.2/A440-26 is the latest North American Fenestration Standard and addresses testing and ratings including Performance Grade and Design Pressure.

However, there is an important 2026 distinction:

NAFS-26 is the latest industry edition, but the 2025 NBC references NAFS-22. NAFS-26 is being proposed for the NBC mid-cycle update.

Therefore, a Canadian project should not automatically specify “NAFS-26 required by code” without checking the jurisdiction and project documents.

Procurement rule: request the test report and verify:

• tested product series
• tested size
• tested configuration
• design pressure
• positive/negative pressure
• water performance
• air performance
• installation/substrate assumptions

A high DP number printed in a brochure is not enough.

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5. Mixed Extreme Climates: Stack the Requirements

The most demanding projects often combine several exposure conditions.

Consider:

• cold + high wind
• hot + coastal
• hot + high UV
• cold + coastal
• hot + coastal + high wind

In these cases, there is no single “extreme-weather window” specification.

The requirements need to be stacked.

This is where generic catalogue specifications become risky.

A window can have excellent thermal performance and still be unsuitable for the project’s wind load. Another can have excellent structural performance but poor solar control.

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What the Numbers Actually Mean

A useful specification should separate the performance parameter from the test method.

This distinction matters because a test method is not the same thing as a product rating, and a product rating is not necessarily the same thing as a code requirement.

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Climate Zone Specification: A Better Procurement Matrix

For architects, contractors and developers, the following matrix is more useful than assigning one universal number to each climate.

For Canadian projects, the final specification should reference the applicable provincial or territorial requirements. The National Research Council explicitly advises project teams to confirm which codes and regulations apply in their jurisdiction.

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What to Send an Aluminum Window Manufacturer

The quality of the quotation depends heavily on the quality of the project information.

For an extreme-weather project, send:

1. Project location
2. Building type
3. Window schedule
4. Opening dimensions
5. Facade orientation
6. Building height
7. Elevations
8. Wall sections
9. Target Uw
10. SHGC requirement if established
11. Design wind pressure or applicable wind criteria
12. Glass specification
13. Finish requirement
14. Hardware requirement
15. Applicable code or standard

This information allows the manufacturer to assess the frame, glass, hardware, drainage and testing requirements together.

Starveil’s aluminum window drawing submission guide covers the information normally needed for a more accurate technical quotation.

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Extreme-Weather Window Specification Example

Instead of writing:

“Aluminum windows suitable for extreme weather.”

A B2B specification should look closer to this:

This gives the architect, contractor and procurement team something measurable to compare.

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Frequently Asked Questions

What are the best aluminum windows for extreme weather?

There is no single configuration that is best for every climate. Hot climates prioritize solar control, cold climates prioritize whole-window thermal performance, coastal climates require appropriate corrosion protection, and high-wind regions require structural and water-performance ratings matched to the project.

What U-factor should windows have in a cold climate?

There is no universal cold-climate Uw requirement. The target depends on the applicable building code, project energy target, window-to-wall ratio and building design. For Canadian projects, check the adopted provincial or territorial requirements rather than using 1.8 W/m²·K as a universal rule. The 2025 Canadian model codes provide the current national framework.

What SHGC is best for desert climates?

A lower SHGC can reduce solar heat gain, but the correct value depends on facade orientation, shading, glazing area and the building’s energy strategy. Do not select a universal SHGC number without evaluating the whole facade.

Are AAMA 2605 windows suitable for coastal areas?

AAMA 2605 is a high-performance organic-coating specification for architectural aluminum. It can be appropriate for demanding exterior exposure, but the complete coastal specification should also consider anodizing alternatives, fasteners, hardware, drainage, pretreatment and maintenance. The current edition is AAMA 2605-26.

What is the difference between DP and PG?

DP refers to design pressure, while Performance Grade is a broader fenestration performance rating within the NAFS framework. The exact rating should be evaluated against the project’s required performance and tested configuration rather than treating a DP number alone as a complete product qualification.

Do hurricane windows need impact glass?

Not every high-wind project has the same impact requirement. Where windborne debris protection is required, the applicable building code or approval pathway determines whether impact-resistant glazing or an approved protective system is required. Impact testing is separate from the static structural evaluation described by ASTM E330/E330M.

How do I specify aluminum windows for a Canadian project?

Start with the project jurisdiction, applicable code, climate/exposure conditions and building energy strategy. Then define Uw, SHGC, air/water performance, structural pressure, glazing, finish and installation requirements. Canada has a national model-code framework, but provinces and territories determine which provisions apply locally.

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Bottom Line

The correct way to specify aluminum windows for extreme weather is not to choose a window from a climate label.

Use this chain:

Climate → Exposure → Performance Risk → Specification Parameter → Test/Calculation → Project Verification

For hot climates, start with SHGC and solar-control strategy.

For cold climates, start with whole-window Uw and condensation control.

For coastal climates, start with finish, hardware and corrosion protection.

For high-wind climates, start with project design pressure and tested fenestration performance.

For mixed climates, combine the requirements instead of compromising one to satisfy another.

For Canadian projects, always confirm the applicable provincial or territorial code before freezing the window specification. The 2025 NBC and NECB are the current national model-code editions, while NAFS-26 is the latest North American fenestration standard but is not yet the edition referenced by the 2025 NBC.

For a project quotation, send the location, elevations, window schedule, opening sizes, orientation and known performance requirements. Starveil can review the aluminum profile, glazing, finish and performance documentation before quotation.

Request a Climate-Zone Window Specification →