Do aluminium window frames corrode near the ocean?

Properly anodised or powder-coated architectural aluminium holds up well in coastal service. What fails first near salt water is hardware — rollers, locks, hinges — and that is steel or zinc regardless of frame material. Specifying marine-grade hardware is the decision that matters on a coastal property.

Do vinyl windows warp in Florida heat?

Rigid PVC expands and contracts more than aluminium across a temperature cycle, and a west-facing Florida elevation in August is a demanding one. Quality vinyl units are engineered for it, but it is the reason vinyl tends to be offered in a narrower, lighter colour range — dark finishes absorb more heat.

Does frame material affect my insurance discount?

No. The wind mitigation credit is based on whether the opening is protected to the required standard and documented on the inspection form. Aluminium and vinyl impact windows that carry the appropriate approval are treated identically.

Guide

Aluminium vs vinyl impact windows in South Florida

Q: Are vinyl impact windows cheaper?

Generally yes, though the gap narrows on large openings where a vinyl frame needs internal reinforcement to reach the same design pressure. On a house made up mostly of wide spans the difference can be smaller than you would expect.

We install aluminium as the default in South Florida. Aluminium is far stiffer, so it carries large spans of heavy laminated glass in narrower frames — and South Florida homes are full of large openings. Vinyl has the better thermal number on paper, but in a climate where cooling load is dominated by solar heat coming through the glass rather than conduction through the frame, the glass specification moves your energy bill much more than the frame material does.

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The stiffness argument, which is the real one

Aluminium is roughly an order of magnitude stiffer than rigid PVC. For an impact window that matters more than it would for an ordinary one, because laminated glass is heavy and the frame has to resist both that dead weight and the design wind pressure without deflecting enough to break the seal or pop the glazing bead.

The practical consequence is sightlines. To reach a given design pressure over a given span, a vinyl frame needs more material — thicker profiles, sometimes reinforcement inside the chambers, sometimes an extra mullion splitting the opening. On a small bathroom window nobody notices. On a wide living-room span facing a pool deck, the difference between a slim aluminium frame and a heavy vinyl one with a bar through the middle of the view is the thing you will look at every day for twenty years.

This is why aluminium dominates the large-opening South Florida market and why vinyl is more common in northern states, where openings are typically smaller and the thermal argument is genuinely decisive.

The thermal argument, in context

Aluminium conducts heat well, which is a disadvantage in a window frame. Quality aluminium impact windows address this with a thermal break — a low-conductivity barrier separating the inner and outer parts of the frame — which closes much, though not all, of the gap.

The part the brochures leave out is proportion. In South Florida the dominant cooling load is solar radiation coming straight through the glass, not conduction through the perimeter frame. The frame is a modest fraction of the opening area; the glass is most of it. Choosing a low-E coating appropriate to your elevations will do considerably more for your comfort and your electricity bill than switching frame material will.

Put bluntly: if energy performance is your priority, spend the money on the glass specification and keep the aluminium frame. Buying vinyl for the thermal number and then accepting a clear, uncoated glass package is the wrong trade.

Coastal exposure and corrosion

The intuition that aluminium corrodes near salt water and vinyl does not is half right, and the half that is wrong matters.

Architectural aluminium is anodised or powder-coated, and a properly finished frame holds up well in coastal service. What actually fails first on a coastal property is hardware — rollers, locks, hinges, operators — and that is true regardless of frame material, because the hardware is steel or zinc either way. Specifying marine-grade hardware near open water is the decision that matters; frame material is close to a side issue.

Vinyl's own weakness in this climate is ultraviolet and heat rather than salt. Rigid PVC expands and contracts more than aluminium across a temperature cycle, and Florida delivers a hard one on a west-facing elevation in August. Darker vinyl finishes are more susceptible again, which is why vinyl frames tend to be offered in a narrower and lighter colour range.

Cost, and where each one wins

Vinyl impact windows are generally less expensive than comparable aluminium, though the gap narrows on larger openings where a vinyl frame needs reinforcement to reach the same design pressure. On a whole-home job made up mostly of large spans, the difference can be smaller than expected.

Vinyl makes sense on smaller openings, on properties where the priority is the lowest defensible cost, and where the thermal number matters to you for its own sake. Aluminium makes sense on wide spans, on anything where the sightline is part of the room, on high design pressure coastal elevations, and where you want the option of darker finishes without worrying about heat.

Both, properly specified, meet code and both earn the same wind mitigation credit. The credit does not care what the frame is made of — only that the opening is protected and documented.

Want this looked at on your own house?

The measure and the written quote are free, and we will tell you what your openings actually need rather than what is easiest to sell.

FAQ

Common questions

For most South Florida homes, aluminium. It is much stiffer, so it carries large spans of heavy laminated glass in narrower frames without an extra mullion through the view. Vinyl's advantage is thermal performance, and in this climate the glass specification affects your cooling bill far more than the frame material does.

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