Performance value terms

Explanation of terms according to EN 410:2011/EN 673:2011

Visible Light Transmittance (Tv, %) is the percentage of incident light in the wavelength range of 380 nm to 780 nm that is transmitted by the glass.

Visible Light Reflectance Outdoors/Indoor (Rv out/in, %) is the percentage of incident visible light directly reflected by the glass.

Colour Rendering Index in transmission, D65 (Ra) is the change in colour of an object because of the light being transmitted through the glass.

Ultraviolet (UV) Transmittance (Tuv, %) is the percentage of the incident UV component of the solar radiation in the wavelength range of 280 nm to 380 nm that is transmitted by the glass.

Solar Energy Direct Transmittance (Te, %) is the percentage of incident solar energy in the wavelength range of 300 nm to 2500 nm that is directly transmitted by the glass.

Solar Direct Reflectance Outdoors/Indoors (Re out/in, %) is the percentage of incident solar energy directly reflected by the glass.

Solar Energy Absorptance (Ae, %) is the percentage of the sun's energy that is absorbed by glass.

Solar Factor or Total Solar Energy Transmittance or g-value (g%) is the total solar radiation transmitted by the glass.

Shading Coefficient (sc) is Solar Factor divided by 0.87. It is a measure of the solar heat gain referenced to 3 mm clear glass which has the designated value of 1.00.

U-Value (Ug, W/m2 K) is the glazing parameter that characterizes the heat transfer through the central part of the glazing, i.e. without edge effects, and expresses the steady-state density of heat transfer rate per temperature difference between the environmental temperatures on each side. Temperature differential according to standard conditions: ∆T=15K°. The lower the value, the greater is the insulating value. EN 673 defines the value with 1 decimal place.

Explanation of Terms According to NFRC 2010

Visible Light Transmittance (Tv, %) is the percentage of incident light in the wavelength range of 380 nm to 780 nm that is transmitted by the glass.

Visible Light Reflectance Outdoors/Indoor (Rv out/in, %) is the percentage of incident visible light directly reflected by the glass.

Color Rendering Index in transmission, D65 (Ra) is the change in color of an object because of the light being transmitted by the glass.

Ultraviolet (UV) Transmittance (Tuv, %) is the percentage of the incident solar radiation transmitted by the glazing in the 300 nm to 380 nm range.

Solar Energy Direct Transmittance (Te, %) is the percentage of incident solar energy in the wavelength range of 300 nm to 2500 nm that is directly transmitted by the glass.

Solar Direct Reflectance Outdoors/Indoors (Re out/in, %) is the percentage of incident solar energy directly reflected by the glass.

Solar Energy Absorptance (Ae, %) is the percentage of the sun's energy that is absorbed by glass.

Solar Heat Gain Coefficient (SHGC) is the sum of the solar direct transmittance and the secondary heat transfer factor of the glazing towards the inside, the latter resulting from heat transfer by convection and longwave IR-radiation of that part of the incident solar radiation which has been absorbed by the glazing.

Shading Coefficient (sc) is Solar Heat Gain Coefficient divided by 0.87. It is a measure of the solar heat gain referenced to 3 mm clear glass which has the designated value of 1.00.

U-Value (Winter Night/Summer Day) is the glazing parameter that characterizes the heat transfer through the central part of the glazing, i.e. without edge effects, and expresses the steady-state density of heat transfer rate per temperature difference between the environmental temperatures on each side. US Standard units are Btu/hr·ft²·F and SI / Metric units are W/m2 K.

Light-to-Solar Gain (LSG) is the ratio of visible light gain to solar gain. LSG = (Visible Transmittance) / (SHGC)

Explanation of terms according to GOST EN 410-2014/ GOST EN 673-2014

Visible Light Transmittance (Tv, %) is the percentage of incident light in the wavelength range of 380 nm to 780 nm that is transmitted by the glass.

Visible Light Reflectance Outdoors/Indoor (Rv out/in, %) is the percentage of incident visible light directly reflected by the glass.

Colour Rendering Index in transmission, D65 (Ra) is the change in colour of an object because of the light being transmitted through the glass.

Ultraviolet (UV) Transmittance (Tuv, %) is the percentage of the incident UV component of the solar radiation in the wavelength range of 280 nm to 380 nm that is transmitted by the glass.

Solar Energy Direct Transmittance (Te, %) is the percentage of incident solar energy in the wavelength range of 300 nm to 2500 nm that is directly transmitted by the glass.

Solar Direct Reflectance Outdoors/Indoors (Re out/in, %) is the percentage of incident solar energy directly reflected by the glass.

Solar Energy Absorptance (Ae, %) is the percentage of the sun's energy that is absorbed by glass.

Solar Factor or Total Solar Energy Transmittance or g-value (g%) is the total solar radiation transmitted by the glass.

Shading Coefficient (sc) is Solar Factor divided by 0.87. It is a measure of the solar heat gain referenced to 3 mm clear glass which has the designated value of 1.00.

Secondary Heat Transfer Coefficient (q_i) is the result of heat transfer by convection and longwave IR-radiation of that part of the incident solar radiation which has been absorbed by the glazing.

U-Value (Ug, W/m2 K) is the glazing parameter that characterizes the heat transfer through the central part of the glazing, i.e. without edge effects, and expresses the steady-state density of heat transfer rate per temperature difference between the environmental temperatures on each side. Temperature differential according to standard conditions: ∆T=15K°. The lower the value, the greater is the insulating value. EN 673 defines the value with 1 decimal place. The value is also provided with 3 decimal places for informational purposes.

R-Value (m2K/W) (thermal resistance) characterizes the ability of the central part of the glazing, i.e. without edge effects, to resist heat transfer from a higher temperature environment to a lower temperature environment. The higher the value, the greater the insulating value. ∆T determined by design location.

Explanation of terms according to ISO 9050: 2003 and ISO 10292: 1994.

Visible Light Transmittance (Tv, %) is the percentage of incident light in the wavelength range of 380 nm to 780 nm that is transmitted by the glass.

Visible Light Outdoors/Indoors (Re out/in, %) is the percentage of incident solar energy directly reflected by the glass.

Colour Rendering Index in transmission, D65 (Ra) is the change in colour of an object because of the light being transmitted through the glass.

Ultraviolet (UV) Transmittance (Tuv, %) is the percentage of the incident solar radiation transmitted by the glazing in the 300 nm to 380 nm range. The relative spectral distribution, Sλ , used to calculate the UV-transmittance is derived from the global solar irradiance given in ISO 9845-1:1992, Table 1, column 5.

CIE damage factor (τdf) is the factor associated with solar radiation in the wavelength range of 300 nm to 600 nm which may contribute to damage of materials.

Skin damage factor (Fsd) is the factor associated with solar radiation in the wavelength range of 300 nm to 400 nm which may contribute to damage of skin.

Solar Energy Direct Transmittance (Te, %) is the percentage of solar energy at normal incidence directly transmitted by the glass. Solar Energy is the radiant energy from the sun having a wavelength range of 300 nm to 2500 nm at an air mass of 1.0, global, per CIE #85: 1989.

Solar Direct Reflectance Outdoors/Indoors (Re out/in, %) is the percentage of incident solar energy directly reflected by the glass.

Solar Energy Absorptance (Ae, %) is the percentage of the sun's energy that is absorbed by glass.

Solar Factor or Total Solar Energy Transmittance or g-value (g%) is the total solar radiation transmitted by the glass.

Shading Coefficient (sc) is Solar Factor divided by 0.87. It is a measure of the solar heat gain referenced to 3 mm clear glass which has the designated value of 1.00.

Secondary Heat Transfer Coefficient (qi) is the result of heat transfer by convection and longwave IR-radiation of that part of the incident solar radiation which has been absorbed by the glazing.

U-Value (Ug) [per ISO 10292] - parameter of glazing which characterizes the heat transfer through the central part of the glazing, i.e. without edge effects, and states the steady-state density of heat transfer rate per temperature difference between the environmental temperatures on each side. 

Explanation of terms according to JIS R 3106: 1998 JIS R 3107: 1998.

Visible Light Transmittance (Tv, %) is the percentage of incident light in the wavelength range of 380 nm to 780 nm that is transmitted by the glass.

Visible Light Outdoors/Indoors (Re out/in, %) is the percentage of incident solar energy directly reflected by the glass.

Solar Energy Direct Transmittance (Te, %) is the percentage of solar energy at normal incidence directly transmitted through the glass. Solar Energy is the radiant energy from the sun having a wavelength range of 300 nm to 2100 nm per Table 2 of JIS R 3106.

Solar Direct Reflectance Outdoors/Indoors (Re out/in, %) is the percentage of incident solar energy directly reflected by the glass.

Solar Energy Absorptance (Ae, %) is the percentage of the sun's energy that is absorbed by glass.

Solar Heat Gain Coefficient (SHGC) is the sum of the solar direct transmittance and the secondary heat transfer factor of the glazing towards the inside, the latter resulting from heat transfer by convection and longwave IR-radiation of that part of the incident solar radiation which has been absorbed by the glazing.

Shading Coefficient (sc) is Solar Heat Gain Coefficient divided by 0.87. It is a measure of the solar heat gain referenced to 3 mm clear glass which has the designated value of 1.00.

U-Value (also called K-Value) for double glaze (single gap) make-ups is the parameter of glazing which characterizes the heat transfer through the central part of the glazing, i.e. without edge effects, and states the steady-state density of heat transfer rate per temperature difference between the environmental temperatures on each side.

U-Value (also called K-Value) for make-ups comprised of two or more gaps is the air-to-air thermal conductance of 39" high glazing and associated air films. Metric units are W/m²K. Surface coefficients of 20.4 W/m²K outdoors & 8.6 W/m²K indoors, at 0° C outdoors and 20° C indoor (°C + 273 = Kelvin).

Explanation of Embodied CO2 Estimation

Embodied CO2 [eq. kg/m2] A1-A3, except for Guardian Nexa™ 6, is estimated based on material Embodied Carbon Factor (ECF), derived from Guardian Glass Regional third-party independently verified and published / current Environmental Product Declarations (EPDs) which are produced to EN 15804 and are compliant with the requirements of ISO 14044, the International Life Cycle Assessment (LCA) standard, and ISO 14025 and ISO 21930, the international standards covering EPD for construction products. The Nexa™ 6 ECF is derived from the LCA of Lower-Carbon production runs and pending verification for conformance to ISO 14040/44, ISO 21930, and the Product Category Rules (PCR) through a program operator and independent reviewer. The Nexa™ 6 ECF values are subject to change based on the critical review process. The new Guardian Nexa™ 6 EPD is expected to be published around mid-2024. The A1–A3 ECF is an estimate of the embodied carbon due to production of that material. The resulting material value should then be multiplied by the square area of glazing to provide an estimate of embodied carbon of the material at the project scale. Embodied CO2 estimates provided by Guardian represent only values associated with the glass components manufactured by Guardian. The estimated values do not represent in any way a plant-specific and/or product specific guarantee.