Where steel wins.
Steel goes to a slimmer sightline than aluminum at the same panel size because steel is stronger pound for pound. For a strict industrial or heritage aesthetic that needs a 20mm or thinner profile, steel is the only material that delivers it on a load-bearing window.
Steel also carries a specific design language: warehouse conversion, Crittall heritage, factory loft. If that is the look the project is committing to, steel is the authentic material; aluminum is approximating it.
Where aluminum wins.
Aluminum does not rust. Steel windows in coastal or humid climates need coating maintenance to prevent rust over time, which is real ongoing work. Aluminum needs no equivalent because it does not corrode the same way; the factory finish stays put for decades.
Energy performance: a thermally-broken aluminum frame insulates at modern code levels (U-factor 0.25 to 0.35). Steel does not have a comparable thermal-break system in production; steel windows run cold. For any cold-climate project, aluminum is the only material that performs without compromise.
Cost: aluminum runs significantly lower than steel at equivalent build quality, even before counting the steel maintenance cost. Sightlines are slightly thicker (typically 30 to 40mm versus 20 to 25mm on steel) but for most residential projects that gap is invisible.
Common questions.
- Are aluminum windows as strong as steel?
- Steel is stronger pound for pound, which is why steel can go to a thinner profile at the same panel size. For typical residential window panels, aluminum is more than strong enough; for very large panels at extremely thin sightlines, steel still wins on structural grounds.
- Do steel windows rust?
- Steel windows have a factory coating that resists rust, but the coating is the only thing protecting the steel. In coastal or humid environments, the coating needs maintenance over time or rust will reach the substrate. Aluminum does not have this problem.
- Which is better for a cold climate?
- Aluminum, by a wide margin. A thermally-broken aluminum frame insulates at modern energy code levels. Steel does not have an equivalent thermal-break system in production, so steel windows run cold and condense in winter.
Project in motion
Trying to pick between aluminum and steel?
We build thermally-broken aluminum windows that match the steel-look sightline for most projects, without the rust maintenance and at a lower price. Send openings for a comparison quote.