Double glazing with Pilkington K Glass™ has a U value of only 1.9, considerably better than conventional double glazing, and as good as triple glazing. Because Pilkington K Glass™ is so neutral in appearance, it is recommended that its presence in a double glazing unit is confirmed on installation.

Pilkington K Glass™ OW can be used as the inner pane (Surface 4) of an IGU to achieve a Ug-value as low as 0.9 when combined with Pilkington Optitherm™ S1 Pro T (Surface 2).

The current industry standard double glazed unit is made up of one 4mm pane of “Low E” (Low Emissivity) coated glass*, one pane of 4mm plain annealed glass and a 20mm cavity of argon gas (make up = 4-20-4). This will provide a centre pane u-value of 1.1 W/m²K.

What are the standard U value measurements?

1. Single glazing U value = 5.6 w/m2K (Watts / square metre Kelvin).
2. Double glazing (with air cavity) U value = 2.8 w/m2K.
3. Double glazing (with argon gas cavity) U value = 2.6 w/m2K.
4. Double glazing with low emissivity glass (with air cavity) U value = 1.8 w/m2K.

One of the most important glass performance measures is U-value—also known as U-factor—which measures the insulating characteristics of the glass, or how much heat flow or heat loss occurs through the glass due to the difference between indoor and outdoor temperatures.

Low-E 4th Surface Technology is a revolutionary way to obtain energy-efficient glazing and indoor comfort by significantly improving thermal performance. Low-e 4th Surface Technology allows double-glazed insulating glass units to achieve 12% better thermal performance than clear glass triple-pane units.

In 2018, Part L building regulations for standard replacement doors and windows specified that a product should have a U-Value no higher than 1.6 for windows, and 1.8 for doors.

In a cold climate a good U-factor for a window is between 0.17 and 0.39. (That’s between R-6 and R-2.5). Lower is better with U-factor–the opposite of R-value, when higher is better. The low end of that range is only achievable with higher-quality triple-glazed windows–windows with three layers of glass.

1.2 W/(m²K)
Modern double glazed units use Low Emissivity Glass (Low-E) and argon or krypton gas in the cavity and the best double glazed windows can achieve a U-value in the region of 1.2 W/(m²K).

1.6 W/m2K
To comply with building regulations, windows (like every other element of your property) must meet a certain minimum U-value. In the case of a window, it’s 1.6 W/m2K. Double-glazed windows, filled with argon, are typically 1.4 W/m2K, while thicker triple-glazed windows can go as low as 0.7 W/m2K.

U-value formula U Value is the reciprocal of all resistances of the materials found in the building element. To calculate the U-Value of the building element the R-Value of all the different components that make up that element will be considered. U-Value (of building element) = 1 / (Rso + Rsi + R1 + R2 …)

calculation for windows In windows there are always three different U-values: Uw (w = window) – overall value of the window. Ug (g = glazing) – U-value of the glazing. Uf (f = frame) – U-value of the frame.