Windows play a significant role in heat gain and loss, impacting our energy efficiency and comfort levels. Understanding these concepts empowers you to make informed decisions when it comes to selecting energy-efficient replacement windows for your home. In this blog post, we will explore how heat is gained and lost through windows, as well as discuss the different window ratings that influence these factors.
Conduction
Conduction is the transfer of heat through direct contact between materials of different temperatures. Heat can pass through windows’ glass, frames, and other components. These materials’ thermal conductivity impacts heat transfer. Window frames like wood and vinyl have low thermal conductivity, which helps reduce heat conduction.
Convection
Convection refers to the movement of heat through the circulation of air or other fluids. Within the window’s airspace, convection currents can form, transferring heat between the window glass and the surrounding environment. Double or triple-pane windows with gas fills (such as argon or krypton) between the panes reduce heat transfer through convection by creating a barrier that limits air movement.
Radiation
Radiation is the transfer of heat in the form of electromagnetic waves. Sunlight is a source of radiant heat that can penetrate windows. While visible light passes through the glass, the infrared radiation (heat) can be absorbed and re-emitted by the materials inside the building, contributing to heat gain. Low-emissivity (low-e) glass coatings on windows and doors help minimize heat transfer through radiation by reflecting a significant portion of the infrared heat back outside.
Window Ratings Affecting Heat Gain and Loss
Here are some of the energy performance metrics used to evaluate how energy-efficient windows are:
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U-Factor. The U-factor measures the rate of heat transfer through a window. It quantifies how well a window insulates against heat loss. Lower U-factor values indicate better insulation. Energy-efficient windows typically have lower U-factor ratings, which means they reduce heat loss and help maintain a more comfortable indoor environment.
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Solar Heat Gain Coefficient (SHGC). The SHGC represents the fraction of solar heat transmitted through a window. It indicates how effectively a window blocks heat gain from sunlight. A lower SHGC value means less solar heat enters the building, reducing the need for cooling. In warm climates, selecting windows with a lower SHGC can help improve energy efficiency and comfort.
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Visible Transmittance (VT). The VT rating measures the amount of visible light transmitted through a window. While not directly related to heat gain or loss, VT is essential for determining how much natural light enters a space. Higher VT values indicate more natural light, reducing the need for artificial lighting during the day.
Get Replacement Windows in Sacramento!
Whether your window installation project is a standalone project or a part of a larger home remodeling endeavor, you can count on the experts at Renewal by Andersen® of Sacramento to provide the best products and services possible. To learn more about energy-efficient replacement window units, give us a call at (916) 779-5800, or fill out our online form to schedule an in-home consultation.
