Energy-efficient window coverings translate into year-round savings on heating and cooling costs.
The more heat loss and heat gain they prevent, the more money will be saved by keeping rooms warmer in winter and cooler in summer. Simple numeric values for product and fabric type can help you gauge the energy efficiency of any plantation shutter or Hunter Douglas product.
Winter Comfort: R-Value
A product’s “R-value” is a measurement of its ability to resist heat flow. In the winter, R-values indicate the ability of walls, roofs and windows to keep heat inside.
The higher its R-value, the more insulation a product provides. The walls and roof of a well-constructed building typically have an average R-value of 25. The low-e double-glazed windows can have an R-value of 3.5.
These windows would allow about seven times more energy to escape per square foot than the rest of the building’s exterior. Windows truly are energy “holes.” This is where Regency Shutters products can have a very positive impact.
Summer Comfort: Solar Heat Gain Coefficient
A product’s “solar heat gain coefficient” (SHGC) is a measurement of its ability to reduce heat gain from the sun. When used with windows, it is the fraction of solar energy striking a window that actually passes through it to heat the room.
SHGC is expressed as a number between zero (none) and 1 (all). The lower a window’s solar heat gain coefficient, the less solar energy it transmits. The SHGC of a standard double-glazed window is 0.76, meaning 76% of the incident solar energy is transmitted through it.
Why are we not using R-value (or its inverse, the U-factor) as a measure of energy efficiency in summer? R-value relates to heat flow due to the inside/outside temperature difference. In summer, solar heat gain is much more significant than heat flow, making SHGC the more important measurement.
The SHGC of our products is measured with standard double glazing, which has an SHGC of 0.76. The SHGC of low-e double glazing varies widely, from 0.70 (high gain) to 0.30 (low gain), making product comparisons less meaningful.
UV Filtering: Protecting Against the “Invisible Enemy”
The ultraviolet light in sunlight can slowly but relentlessly cause damage to your furnishings. In time it fades wood floors, furniture, upholstery, draperies, carpeting and artwork. Prolonged exposure to sunlight causes natural, undyed fabrics to turn yellow, weakening their fibers and making them look old and worn prematurely.
The right window covering can be very effective in blocking ultraviolet rays. Such effectiveness is measured in terms of a “% UV blockage” rating. The higher the rating, the greater the UV protection. Hunter Douglas window coverings typically will block 86% or more of UV radiation.