Spacers  separate  multiple panes of glass  in a window and maintain the space  between them.  Spacers and the sealants used to hold them in place are referred to as spacer systems,  and efficient ones help deliver the benefits consumers want:

  • They seal the space between the glass panes to avoid fogging and prevent efficiency-boosting gases from leaking out
  • They expand and contract along with the rest of the window
  • Provide a gas-tight seal that prevents the loss of any special low- conductance gas in the air space
  • In cold climatesspacer systems can reduce heat losscondensation, and water damage 
  • Non-metallic spacer systems are most efficient in blocking heat and cold transfer and reducing condensation. Their flexibility allows them to expand and contract along with the rest of a window, which protects the seal from cracks. 
  • Warm-edge spacer systems block heat and cold from passing through a window by blending metallic and non-metallic materials. This also cuts condensation. 
  • Metal spacer systems are common, but heat and cold can pass easily through them. This makes it more difficult for heating and cooling systems to maintain interior temperatures, and risks condensation.


About Us

provides unbiased information and education to the public on the energy efficiency, technical, and human considerations that influence window selection and use. The EWC collaborates with allied organizations, educational institutions, and government agencies that promote energy efficiency in residential windows. We do not sell, service, install, or recommend products, or endorse manufacturers. Descriptions and specifications of the products in the Window Selection Tool are provided by the manufacturer. The EWC is not liable for any manufacturing defects or inaccurate product descriptions and specifications and does not guarantee the performance of NFRC-certified windows, doors, and skylights.

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National Fenestration Rating Council
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Greenbelt, MD 20770
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