by Peter J. Davey
The dog days of summer are here. Temps are rising, AC units are cranking, and utility bills are increasing with every degree Celsius or Fahrenheit. Driving throughout New England, I see curtains drawn, shades down, and blinds closed during the best part of our bright, sun-shiny days.
As president of American Window Film, Inc. and one who works with architects and interior designers, I know how disappointing it is to realize that efforts to showcase extraordinary views through architecturally and strategically placed windows cannot be appreciated fully behind window treatments. Indeed, sun beating down upon windows causes indoor environment heat gain and nuisance glare. However, professionally installed solar control and low-e window films are “hot products” engineered to beat summer’s heat gain without compromising those views that are often the reason properties are leased, purchased, and highly valued.
Solar control window films and low-e (short for wow emissivity) work differently. Solar control films focus on the solar energy spectrum. In order for solar films to be effective, window glass needs exposure to sunlight. Low-e window films address radiant heat and are designed to reduce the transfer of radiant heat from one side of window glass to the other rather than allowing the glass to absorb it. Radiant heat is based solely on the temperature of an object, i.e., window glass.
There are innovative window films on the market today that include both sun control (solar spectrum) and low-e (radiant heat) control benefits. These films reduce the solar energy entering a building and are additionally engineered to help prevent the transfer of radiant heat from one side of window glass to the other. Utilizing different technologies, window films with both solar control and low-e properties increase energy conservation by helping to reduce heat loss during colder months and heat gain during warmer months. This makes them an effective year-round window film for our New England climate.
Building owners and property managers should consider radiant/solar heat control films as insulation for windows. A single-pane window loses 20 times as much heat as the same area in an adjacent well-insulated wall. This leads to nearly 30% of all energy used to heat and cool buildings (and homes) going out the window. These highly engineered window films can improve the insulation value of a typical single-pane window to close to that of a double-pane; a double pane to close to that of a triple-pane. They achieve this at a fraction of the cost, disruption, and time required to replace existing windows. Architects, interior designers, and their clients will appreciate the high optical clarity of these highly engineered and innovative window films, while they perform well in all climates and deliver value-added, uncompromising views.
The following may be helpful when considering window film for a particular application. Solar heat gain coefficient (SHGC) measures the effectiveness of a film in preventing solar energy from entering a building. Emissivity is the ability of a material to emit or absorb radiant heat and is only one of the variables used to calculate the U value of a window. U value represents the amount of heat that passes through a square foot of glass in 1 hour for every one degree Fahrenheit temperature difference between interior and exterior environments, a measure more consistent than emissivity within the window and window film industries. The lower the U value, the better insulated the window or window film.
Peter J. Davey is president of American Window Film, Inc.