Energy Efficiency & Performance
The fenestration performance cluster (PURE windows, not HVAC or wall insulation): a U-factor ↔ R-value converter (R = 1 ÷ U), an SHGC / solar-heat-gain reference, the signature ENERGY STAR / IECC climate-zone requirement checker, a fenestration energy-savings estimate (a heating-season delta that defers the full load calc to an HVAC pro), a replacement payback, and a visible-transmittance / condensation-resistance reference.
Typical published planning values / code minimums — NOT a certified design or a compliance sign-off. Actual egress compliance and energy performance depend on your local building code (AHJ), climate zone, the exact product’s NFRC-rated U-factor & SHGC and the installation; confirm against local code and the manufacturer’s NFRC label, and consult a pro. Structural headers for enlarged openings, whole-building heat-load / HVAC sizing and code certification are set by code and a professional — not engineered here.
U-factor ↔ R-value converterConvert a window U-factor to R-value and back with R = 1 ÷ U. Enter the NFRC-rated U-factor or R-value and read the reciprocal, plus a U/R chart by glazing.SHGC / solar-heat-gain referenceFind the target window SHGC by climate goal: low to reject heat in cooling climates, higher to capture solar gain in heating climates, with a labeled chart.ENERGY STAR climate-zone checkerCheck a window U-factor and SHGC against ENERGY STAR 7.0 and IECC 2021 requirements by climate zone, with a Meets / Does not meet verdict for each snapshot.Window energy-savings estimatorEstimate annual heating-season savings from lower-U-factor windows: area × ΔU × heating-degree-days × 24 ÷ 1000 ÷ efficiency × your energy price.Replacement-window paybackWork out replacement-window payback in years: project cost ÷ annual energy savings. Enter your quote and the yearly saving to see the simple break-even.VT & condensation referenceReference for the NFRC visible transmittance (VT) and condensation resistance (CR) numbers by glazing — single, double clear, double low-E and triple low-E.
Every Energy Efficiency & Performance tool is calculated server-side — visible immediately — with its formula, a worked example and a reference table, and works on the measurements you take and the prices you enter from your own quotes. Background reading is in the guides.