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.

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.