Key Metrics of Window Performance

Beautiful, sleek and energy-efficient windows are all the rage in these modern times. From increased energy savings to reduced condensation issues, improved lighting and ventilation and better comfort, there are a lot of reasons to finally get rid of your old, shabby windows and replace them with new, energy-saving units. In this article, we break down the metrics used to assess window performance. 

• U-Factor. The rate of heat transfer through a product is measured by the U-factor. It considers conductance, airflow and heat radiation or reflection of the window glass. Its values range from 0.20 to 1.20. The lower the U-factor, the better the window insulates.
• Solar Heat Gain Coefficient (SHGC). It is the fraction of incident solar radiation admitted through a window. Its values range from 0 to 1. The lower the solar heat gain coefficient of a window, the less solar heat it transmits.
• Visible Transmittance (VT). This indicates the fraction of visible light transmitted through a window. As a whole-window rating, visible transmittance includes the impact of the frame area. It varies between 0 to 1, with most double- and triple-pane replacement windows possessing ratings between 0.30 to 0.70. The higher the visible transmittance of a window, the more light is transmitted.
• Air Leakage (AL). This measures the heat loss and heat gain occurring through cracks in the window assembly. An air leakage rating of 0.30 or less is required for ENERGY STAR certification.
• Condensation Resistance. This measures how well a window unit resists condensation on the inside surface. Its values range from 1 to 100, with the higher number being the better product to resist condensation.
• Sound. A high-performance window provides reduced sound transmission. In order to reduce noise, the window should minimize air infiltration and use double glazing.

Renewal by Andersen® of Central Pennsylvania is a premier source of replacement patio doors and windows, including casement windows and sliding windows, in and around Lancaster, PA. Our certified team is committed to providing the comfort and efficiency you need through industry-leading products and outstanding customer service. Call us today at (717) 929-8610 or fill out our contact form to request a free, no-obligation estimate.