What’s the thermal conductivity measurement unit?

When evaluating the thermal insulation performance of a glass product,we usually know that clear& tinted single piece glass is 5.84,Single silver low-E insulated glass 1.8,and double silver low-E is 1.55-1.65.The lower the value,the better thermal insulation performance the glass has.
But What does the value mean and the measurement unit?
Actually the measurement unit is W/M2.k,which means watt/square meter/Kelvin,it’s under same confirmed air condition,the heat transfered throught the glass products.
While even this measurement unit,there’re many different conditions depend on different client.

What's the thermal conductivity measurement unit?

The most widely used condition is American LBNL Ashare NFRC 100-2010 SUMMER standard:
Room temperature: 24°
Outside temperature: 32°
Glazing oriented windward, wind speed: 2.75 m/s
Sky temperature: 32°
Sky emissivity: 1.0
Incident solar power: 0 W/m2

NFRC 100-2010 winter standard:
Room temperature: 21°
Outside temperature: -18°
Glazing oriented windward, wind speed: 5.5 m/s
Sky temperature: -18°
Sky emissivity: 1.0
Incident solar power: 0 W/m2

While in European areas,they use another standard:EN673,there’s no summer and winter difference as there’s not big difference between winter and summer temperature.
Despite W/M2.K,there’s another measurement unit that shows the thermal conductivity :ft2•h•°F/BTU ,which means hour/square foot/°F.
It’s quite different unit.Sometimes clients mentioned glass unit is 0.3,many sales don’t believe this and think it must be incorrect and the glass U v value couldn’t be this low.While what the client mentions is hour/square foot/°F,not W/m2.k.
To transfer the unit, 1hour/square foot/°F =5.68w/m2.k,so don’t make mistake.
Morn is your turnkey architectural glass manufacturer supplying all kinds of tempered glass,laminated glass and insulated glass,welcome contact us for more info.

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