Glass · Insulating units
Glazing configurator: build a double or triple unit
Build the unit pane by pane — thickness, laminate, the low-E coating and its face, cavity and gas — and the section, the Ug, the weight and the make-up follow as you type. The Ug is the same EN 673 calculation as the U-value calculator and the weight the same rule as the weight calculator, 2.5 kg/m² for every millimetre of glass, so the three pages always agree. Faces are numbered from outside, every glass surface counted.
Everything runs in your browser and nothing you type is uploaded. The Ug of this page and of the U-value calculator are the same figure for the same unit, and so are the weights here and in the weight calculator: one engine, tested against both.
How it is worked out
Ug, centre of the pane. EN 673, with the U-value calculator's own code and values: 1/Ug = 1/he + Σ 1/hs + Σ d/λ + 1/hi, with he = 23 and hi = 8 W/(m²·K) and λ = 1.0 W/(m·K) for glass. Each cavity is radiation plus gas: hr from the emissivity of the coated face against plain glass (0.837), hg from the Nusselt number of the gas at 283 K and ΔT = 15 K. The gas table and the coating classes are the U-value calculator's.
Weight. As the weight calculator: glass at 2500 kg/m³ (EN 572-1), 2.5 kg/m² for every millimetre, and PVB at 1070 kg/m³. The gas and the spacer are not counted.
Faces. Numbered from the outside face of the outer pane, every glass surface counted, the two inside a laminate as well. In a 4 / 16 / 4 unit the cavity lies between faces 2 and 3; with a 6.6.2 outer pane it lies between faces 4 and 5. Some catalogues count a laminate as one pane with two faces: check which way your supplier counts before you order.
How the make-up is written. From outside to inside, panes and cavities separated by a slash. A laminate is written ply.ply.films: 6.6.2 is two 6 mm plies with two 0.38 mm PVB films (in Spanish, 6+6.2). The gas follows the cavity width, Ar, Kr or Xe; air is not written. The coating goes after its pane, with its face: 4 / 16 Ar / 4 low-E (face 3).
What this page does not do
- Centre-pane only. No spacer, no edge, no frame: the window is always worse. Take this Ug to the window U-value calculator.
- One coating per cavity, on a face that looks into it. As the U-value calculator: the outside faces keep he = 23 and hi = 8, so coatings on face 1 or on the room-side face are not modelled.
- The interlayer has no thermal resistance here. The U-value calculator has no value for it, so a laminate counts as its glass; that can only make Ug slightly higher.
- No sound reduction, no solar gain, no light transmission. Rw cannot be added up from the layers: ask for the tested figure, and read the acoustic glazing guide before choosing the panes. The face of the coating changes the solar gain, which this page does not calculate.
- Not a thickness check. Whether the panes stand the wind is a separate calculation: the wind-load thickness calculator, with the size above.
- Vertical glazing, nominal gas fill, standardised conditions: a declared value comes from the manufacturer's tested figure for the exact coating.
What does 6.6.2 / 14 / 4 mean?
It is a double glazed unit written from outside to inside: a laminated pane of two 6 mm plies bonded with two 0.38 mm PVB films (0.76 mm), a 14 mm cavity, and a 4 mm pane. In Spanish the same laminate is written 6+6.2. A gas is written after the cavity width, 16 Ar for argon; air is usually not written.
Does it matter for the U-value which face the low-E coating is on?
Not for the centre-pane Ug by EN 673: it counts the coated cavity, not which of its two faces carries the coating, so face 2 and face 3 give the same Ug. The face does change the solar gain, which this page does not calculate: follow the coating maker's instructions.
How heavy is a double glazed unit?
Only the glass and the interlayers weigh: 2.5 kg/m² for every millimetre of glass and 1.07 kg/m² for every millimetre of PVB. A 4 / 16 / 4 unit is 20.0 kg/m², a 6.6.2 / 14 / 4 unit 40.8 kg/m².