If you’re looking to purchase replacement windows and patio doors, thermal performance, the Energy Savings and comfort maintenance capabilities of the windows and patio doors, should be a big consideration in choosing which brand to use on your project.
Most reputable Window Manufacturers have their windows and patio doors evaluated by an independent test laboratory, accredited by the National Fenestration Rating Council (NFRC). These laboratories use the NFRC 102-2020 – Testing Procedure to determine the thermal performance of each brand and model of window or patio door.
Based on stringent physical testing and engineering design review, the test lab issues a detailed report that substantiates an “performance factor” of the window or patio door in five areas of thermal performance. These 5 performance factor numbers provide a concrete way to compare the energy and comfort performance of the windows and patio doors being offered to you by the contractors and window companies you are considering for your project.
We at Jantek Windows publish the Thermal Performance Factors for all of our window and patio door models on the product pages of our website www.jantekwindows.com. but we want to give a quick guide to understanding what the Thermal Performance Factors on the NFRC Label mean to help you determine how well a product will perform the functions of helping to cool your home or building in the summer, warm your building in the winter, keep out wind, and resist condensation.
So now let’s take a look at the NFRC performance Factors and understand what each signifies.
U-Factor
U-factor measures how well a product prevents heat from escaping. The rate of heat loss is indicated in terms of the U-factor (U-value) of a window assembly. U-Factor ratings generally fall between 0.18 and 1.20. The lower the U-value, the greater a window’s resistance to heat flow and the better its insulating value. A lower U-Factor keeps your building warmer in the winter and cooler in the summer.
Solar Heat Gain Coefficient
Solar Heat Gain Coefficient (SHGC) measures how well a product blocks heat caused by sunlight. The SHGC is the fraction of incident solar radiation admitted through a window (both directly transmitted and absorbed) and subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a window’s solar heat gain coefficient, the less solar heat it transmits in the house. In colder climates you want a SHGC factor somewhere in the “mid .20’s” since you have a longer heating season. In the warmer climates, you want to see an SHGC in “High Teens” since you have a longer cooling season.
Visible Transmittance
Visible Transmittance (VT) measures how much light comes through a product. The visible transmittance is an optical property that indicates the amount of visible light transmitted. VT is expressed as a number between 0 and 1. The higher the VT, the more light is transmitted.
Air Leakage
Air Leakage (AL) is indicated by an air leakage rating expressed as the equivalent cubic feet of air passing through a square foot of window area (cfm/sq ft). Heat loss and gain occur by infiltration through cracks in the window assembly. The lower the AL, the less air will pass through cracks in the window assembly.
Condensation Resistance
Condensation Resistance (CR) measures the ability of a product to resist the formation of condensation on the interior surface of that product. The higher the CR rating, the better that product is at resisting condensation formation. While this rating cannot predict condensation, it can provide a credible method of comparing the potential of various products for condensation formation. CR is expressed as a number between 0 and 100.
So now you have a better understanding of how to use the NFRC Factors and Label to compare the energy and comfort performance of replacement window and patio doors. This is just one piece of the total picture, but it is a very important criteria in your up-front research to selecting the best replacement windows and patio doors for your project.
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