Air Leakage (AL)

Measures how much air will enter a room through a product. AERC certified products with lower air leakage may result in fewer drafts and help to reduce heating costs.

Commercial Baseline Window

he baseline window used for commercial secondary window ratings is a single-pane clear glass aluminum frame window. This represents an average window in older commercial building stock.

Emissivity

How readily the surface of a material gives off heat by radiation. Many common building materials have “high” emissivity (around 0.9 out of 1.0 being a perfect emitter), while materials or objects with metallic coatings or surfaces have “low” emissivity (around 0.15 or less).

Low-Emissivity (Low-E)

Nearly invisible metallic coating on inside surface of double-pane glass windows, storm windows, and interior window panels that improves the energy efficiency of the window and the thermal comfort of occupants.

Solar Heat Gain Coefficient (SHGC)

Measures how well a product can resist unwanted heat gain. AERC certified products with lower SHGC means there is less heat gain, which may reduce cooling costs, while products with higher SHGC means there is more heat gain, which may reduce heating costs.

U-Factor (U-value)

Measures how well a product can retain heat and keep it from escaping from the inside of a room. AERC certified products with a lower U-Factor means there is less heat loss and should be considered by those concerned about heating costs.

Visible Transmittance (VT)

Measures how well a product is designed to effectively light your home with daylight. AERC certified products with higher VT means more light enters, which may help reduce need for artificial lighting, leading to reduced utility costs.

The AERC Energy Rating Label