What is Fenestration?
Any opening in a building's envelope including windows, doors and skylights. People from windows and doors industry are constantly improving and re-designing their products to meet the needs of their customers. To know how they can benefit from the new technologies, customer must be aware of the following facts about their windows. We spend thousands of Bucks every year to cool our homes and businesses. That is why it is so important to understand the role that windows play in how buildings use energy. One of the best ways to measure the effect of windows on building energy use is known as a U-value rating.
U-Value
U-value measures how well a product prevents heat from escaping. The rate of heat loss is indicated in terms of the U-value of a window assembly. U-value ratings generally fall between 7.7 w/sq.mK and 1.1 w/sq.mK. The lower the U-value, the greater a window's resistance to heat flow and the better its insulating value.
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.
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, 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.
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| Products that fill openings in a building envelope, such as windows doors, skylights, curtain walls, etc., designed to permit the passage of air, light,
vehicles, or people. |
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