Thermal Performance Information
R-Value is a measure of resistance to heat gain or loss. The higher the number, the better a product is at resisting heat loss.
U-Factor, the reciprocal of R-Value, is the measure of the rate of heat loss through a material. Thus, in all aspects of home design, one should strive for the lowest U-Factors possible because the lower the U-Factor, the less heat that is needlessly escaping.
Windows with "clear" glass are the least efficient, while windows with Low-E are much more thermally effective. The best performing windows are those using Low-E/Argon glazing. With this glazing, all Harvey vinyl windows are ENERGY STAR® qualified throughout the country.
A detailed listing of U-Factors and other thermal performance data for Harvey Manufactured Products is available in PDF format, and requires the FREE Adobe
Acrobat Reader.Please note that U-Factors are subject to change without notice.
Download the U-Factor Thermal Performance Chart
State Energy Code Information
Some states such as Massachusetts have enacted more stringent Energy Code guidelines that require the use of special glazing such as Low-E glass in replacement windows. Please refer to the state building codes for specific guidelines.
Massachusetts Energy Code
The Massachusetts Energy Code states that all replacement windows shall have a maximum U-Factor of 0.44 as of January 1, 1999. All windows must be NFRC (National Fenestration Rating Council) certified and labeled as such.
January 5, 1999 Amendments
Exception 1: Criteria for NFRC listing/labeling and maximum U-0.44 are not required if the existing window(s) are true divided light (i.e. single thickness multi-pane sashes with structural muntin bars) and being replaced with "like kind" units. This exception additionally requires that a storm window be installed over the replacement window.
Exception 2: Criteria for NFRC listing/labeling and maximum U-0.44 are not required for basement windows with a unit height up to 24", whether or not the basement is a conditioned space.
