Condensation Resistance (CR) measures how well a product resists the formation of condensation – water, water droplets, frost and ice that form on windows when the temperature of the window falls below the dew point temperature for that particular glass, and the dew point is also affected by the amount of moisture or humidity in the air and the ambient room temperature. CR is affected by the U-factor in that the lower the U-factor (the less the window transmit heat) the lower the CR. CR is expressed as a number between 1 and 100. The higher the number, the better a product is able to resist condensation. CR is an optional rating, and manufacturers can choose not to include it on their NFRC labels. In addition to U-factor, other characteristics of a window that can lower its CR are double and triple glazing, low-e coatings and non-thermally conductive framings such as wood or vinyl rather than metal, and non-thermally conductive spacers between window panes. LEED for Homes does not have any requirements with respect to Condensation Resistance ratings.