Question

In an ordinary double-pane window, about half of the heat transfer is by radiation. Describe a practical way of reducing the radiation component of heat transfer.

Short answer

Answer: A practical method to reduce radiation heat transfer in a double-pane window includes the use of low-emissivity coatings, vacuum insulated glass, or alternative window designs and techniques, such as triple-pane windows, gas-filled windows, external shading devices, and reflective films.

Step-by-step solution

Understanding Heat Transfer

Heat transfer can occur through three mechanisms: conduction, convection, and radiation. In a double-pane window, heat is transferred through the glass panes by conduction and between panes by convection and radiation. Since about half of the heat transfer occurs via radiation, we will look for ways to minimize this specific component.

Reducing Heat Transfer by Radiation

Radiation occurs when heat is transferred through electromagnetic waves, without being in direct contact with the material. In a double-pane window, we can reduce heat transfer by radiation by using materials with low-emissivity properties or by employing special coatings on the window surfaces.

Low-Emissivity Coatings

One practical solution to reduce radiation heat transfer is to apply low-emissivity (low-e) coatings to the surface of the window panes. Low-e coatings are thin, transparent layers made of metallic particles that reflect infrared light while still allowing visible light to pass through. By reflecting infrared light (which carries heat), low-e coatings reduce the amount of heat transferred through the window panes by radiation.

Vacuum Insulated Glass

Another approach to reduce radiation heat transfer is to use vacuum insulated glass (VIG) in double-pane windows. VIG windows have a vacuum gap between the panes, which helps to eliminate the conduction and convection components of heat transfer, leaving only the radiation component. In combination with low-e coatings, VIG windows can significantly lower radiation heat transfer.

Alternative Window Designs and Techniques

Other practical methods to reduce radiation heat transfer include the use of triple-pane windows, gas-filled windows, external shading devices, and reflective films. These solutions can be combined or used individually, depending on the specific requirements and budget of the project. In summary, a practical way to reduce radiation heat transfer in a double-pane window can include the use of low-emissivity coatings, vacuum insulated glass, or other alternative window designs and techniques to minimize heat transfer by radiation.