Glass Performance Calculator

A single pane's U-value is roughly 5.6–6.0 W/m²K and barely changes with thickness, because the bottleneck is the air films on each face, not the glass. Multi-pane units drop U by trapping a low-conductivity gas gap: a clear 4/16/4 double unit reaches about 2.8, adding a soft low-E coating reaches 1.4, argon fill reaches 1.1, and a triple low-E argon unit reaches 0.7 W/m²K. The calculator above estimates U from the build you select; certified values come from NFRC or EN 673/EN 674 lab testing.

They are the same number with two names. SHGC (Solar Heat Gain Coefficient) is the North American term; g-value is the European one. Both express the fraction of solar energy a window passes through — direct transmission plus secondary heat re-radiated inward — on a 0 to 1 scale. Clear single glass sits at about 0.86, meaning 86% of the sun's energy gets through; a solar-control low-E coating can pull that to 0.40 or lower while keeping visible light reasonably high.

STC is measured in a lab, not calculated, but the estimating rule is the mass law: every doubling of glass surface mass buys roughly 5–6 STC points, so 4 mm (STC 28) to 10 mm (STC 35) tracks exactly that. Laminated glass beats a monolithic pane of the same mass by 3–7 points because the PVB interlayer damps vibration. Dissimilar-pane doubles (6/16/4) add another 3–4 points by splitting the resonance frequencies of the two panes.

Usually not. A triple unit adds mass but creates two coupled air springs that resonate together, so STC lands at 36–37 — about the same as a clear double unit and two points below a good dissimilar-pane double. Acoustic engineers routinely specify a 6/16/6.8 laminated double over a generic triple. Triples win on U-value; laminated dissimilar doubles win on noise.

As guardrails: mild climates (coastal California, Mediterranean) find U 2.8 acceptable; temperate zones with heating (most of the US, UK, central Europe) want 1.4 or better; cold continental and Nordic climates specify 1.1 down to 0.7. Below about 0.9 W/m²K the center-of-glass improvement gets progressively eaten up by frame and edge-of-glass losses — that is the tipping point where money moves from glass to frames.

Depends on the coating family. High-solar-gain (hard coat) low-E blocks long-wave heat but passes most solar energy — SHGC 0.60–0.65 — designed to keep winter sun coming in. Low-solar-gain (soft coat) low-E reflects the near-infrared part of sunlight — SHGC 0.35–0.45 — cutting summer heat while visible light transmission stays 60–70%, so rooms stay bright without the bake.

They are near-equivalent single-number sound ratings — Rw (the European, from EN ISO 717-1) typically lands within 1–2 points of STC (the American, from ASTM E413) for the same glazing. European datasheets quote Rw plus spectrum adaptation terms (C, Ctr); the Ctr term matters for traffic noise because it penalizes performance at low frequencies, where STC is loosest. If a datasheet shows Rw(Ctr) = 38 (-4), expect real traffic-noise performance closer to 34.