Low-E Glass for Hot Afternoons

Stand inside a west facing room at four in the afternoon and put a hand on the glass, then put the same hand on the glass of a Low-E unit, and the difference explains why the notes at san bernardino new windows petersburg4u start with coatings. New windows in San Bernardino, CA face long, intense sun, so the invisible layer on the glass does a lot of the work, and the same unit that feels cool at four o'clock also keeps the furniture from fading near the Verdemont foothills where the sun is harshest.

What Low-E means

Low-E stands for low emissivity. A microscopically thin metallic coating is applied to the surface of the glass, and it reflects heat while letting visible light through. It is placed inside the insulated glass unit, on one of the surfaces facing the air gap, so it is protected from scratches and cleaning.

Solar heat gain

The solar heat gain coefficient, or SHGC, is a number from zero to one that shows how much sun heat passes through the window. A low number blocks more heat. In the valley below the San Bernardino Mountains, a low SHGC is the goal on west and south walls where cooling costs the most in summer.

U-factor and winter nights

The U-factor measures how much heat leaks through the window by conduction. Lower is better. San Bernardino has cold winter nights, especially near Cajon Pass, so a window with a good U-factor keeps heat in during winter as well as out during summer. An argon fill between the panes improves it further.

Double pane and triple pane

A double pane unit is the standard, with two layers of glass and a sealed air space. A triple pane unit adds a third layer, which helps with noise and insulation but adds weight. For most homes in the Inland Empire, a good double pane with a Low-E coating and a warm edge spacer is enough.

Reading the label

The NFRC label on each new window lists the U-factor, SHGC, visible transmittance and air leakage. Comparing the numbers across brands is straightforward, and the label is the best proof of what the glass does, far better than a salesperson's description of it. Sample glass held up in the room shows the real tint, since a showroom light hides the cast some coatings give. Glass that looks tinted is not always better, since a clear Low-E coating can block more heat without darkening the room.