# How Is Window U Value Calculated?

## What is window U value?

The U-Factor measures how well the window in- sulates.

While the U-Factor can take any value, in general for windows it ranges from 0.20 to 1.20.

The lower the U-Factor, the better the window insulates.

The SHGC measures how much of the sun’s heat comes through the window.

It can range in value from 0 to 1..

## What is the minimum U value for a window?

1.6 W/m2KTo 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.

## What is the U value of a cavity wall?

A range of U-values are indicated below for the purposes of comparison only: Solid brick wall: 2 W/(m²K) Cavity wall with no insulation: 1.5 W/(m²K). Insulated wall: 0.18 W/(m²K).

## What is U value of double glazing?

1.1 W/m²KThe 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 is a good window U value?

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.