By Laura McMahon and John Parker
Hawthorne House at 3450 North Lakeshore Drive in Chicago is not a house at all, but a 40-story apartment building with an estimated 500,700 square feet of living and public space, and an underground parking garage. Built in 1968, Hawthorne House is a Class A apartment building containing 455 residential units. And, the concrete constructed building offers residents an unobstructed panoramic view of Lake Michigan and the Chicago Skyline.
The building’s windowed facade receives full sun much of the day with unobstructed views — views that are appreciated. Indeed its location immediately across the road from the landmark Belmont Harbor on Lake Michigan also offers omni-directional views of the City with no overshadowing from nearby buildings. The facility also includes large-windowed public spaces that receive significant solar exposure.
The building offers two-bedroom, two-bath apartments, with almost all of its units set at a 45-degree angle to Lake Michigan, so that coveted views of Lake Michigan are possible from the majority of the windows.
The building has older dual pane windows, central air and heating, a rooftop pool surrounded by a wall of windows and open to the elements above, as well as a windowed fitness center overlooking Lake Michigan.
The Solar Heat Gain And Glare Problem
But building management encountered a problem. Direct solar exposure caused public spaces, especially the fitness area to experience glare and heat. This made it difficult for residents to enjoy their experience. Additionally, this penetrating solar energy created excessive heat build-up and uncomfortable temperatures.
Installing new windows on all 40 stories was cost-prohibitive and the return on investment would have taken decades to recover the cost. In addition, the building is one if the very few locations on Lake Shore Drive that still offers market-rent apartments; nearly all of the other buildings along this prestigious roadway have been turned into luxury condominiums.
John Parker, president of the International Window Film Association and partner of National Security & Window Filming, based in Oak Forest, IL, was contacted to meet with the Hawthorne’s key staff to evaluate what application of window film would be best for the facility. National Security & Window Filming is a family-owned and-operated business with more than two decades of experience in the installation and service of window films.
The Cost-effective Solution
Before taking any action, Laura McMahon, the asset manager for the building, estimated the return on investment with help from National Security and Window Filming. As director of asset management for J.L. Woode (owner of Hawthorne House) since July 2007, McMahon is responsible for the day-to-day property and asset management decisions for the operations of the multi-family, office, retail, and hotel portfolios. 
The computations listed below estimated the annual savings for this project.
Of course, the cost of energy-saving window film depends on the size of the window surface and the performance specifications of the window film. It is estimated the Hawthorne House’s common areas alone have over 150 windows, each about 80 square feet.
(To provide a general guide on energy saving, the United States Navy investigated the energy reduction benefits of solar control window film and calculated window film saves 17.32 kWh per year for every square foot installed window film on west facing windows with a shading coefficient of 24. At .10 cents a kWh, a low average cost in the U.S., means window film may save a $1.73 per square foot a year. With an estimated 58,000 square feet of glass, then the potential annual savings is more than $100,000.)
Before considering the professional installation of window films at Hawthorne House, the existing windows need to be functionally sound. Functionally sound windows should have few or no failed seals, limited air leakage, and the frames should be in good condition.
Parker and his team came up with a solution and presented it to facility management to install interior window film designed to reduce solar heat gain from solar load and sun damage, all with minimal darkening of the fabulous views from the rooms. The window film selected is rated by the National Fenestration Rating Council for its near zero solar heat gain coefficient (SHGC), while allowing in up to 70% of natural daylight. The window film also came with a 15-year manufacturer warranty. The International Window Film Association provides specialized software called “e-film” that provides calculations based on a variety of building inputs such as square feet, HVAC factors, and other information to help determine the best window film to achieve the goals wanted.
Technologically-advanced window film was selected to reduce solar heat load and glare while not changing the look of the building. Another benefit was reduction of ultraviolet degradation on wood flooring, carpeting, fabrics, and window treatments. Other benefits include the reduction in the checkerboard appearance of different windows from street level, since fewer people needed to use draperies to block-out the sun’s glare — especially on the higher floors.
Once agreed, the National Security and Window Filming team began to install window film. The plan called for window film being installed in the public spaces and also any vacant apartments. As tenants move out, the team arrives to install window film. McMahon noted that some existing tenants specifically requested to have the window film installed in their apartments to help protect their furnishings, and they also noticed the interior had less heat build-up.
The facility management team tracked their progress by measuring various areas and substrates to determine temperature gradients and noted as much as a 20-degree delta (or reduction) in temperatures of different surfaces.
“Now on hot summer days, the HVAC system can easily handle the cooling load while maintaining electrical consumption, and the building now has extra cooling capacity,” said McMahon.
Energy-saving film has been used as a way to reduce the excessive solar heat gain that occurs when a buildings windows face the sun. Building owners and operators worldwide are using energy-saving film as a way to reduce their heating, ventilation and air conditioning load and lower their energy costs.
Some window films have micro-thin, metal coatings. The metal coating is applied using vacuum-based technologies such as vapor deposition or sputtering. A second layer of film is laminated over the metal coating to protect the metal. A scratch-resistant coating may also be applied to protect the film during normal window cleaning. An adhesive layer is also applied to the film side that faces the glass and is protected by a removable release liner until just before the film is applied to the window. UV absorbers are added to the polyester film layers, the adhesive layer, or both to protect from UV deterioration. This last process protects not only the window film, but also interior furnishings and people by reducing the sun’s UV rays by 99%. Many window films are warranted by the manufacturer to last for 15 years or more.
Energy-saving window film may offer a great return on their investment due to the combination of reduced solar heat gain and a lower installation cost compared to such things as window replacements. Studies by the International Window Film Association have shown that window films, when professionally-installed on structurally sound single or double-pane windows, may reduce energy consumption by as much as 30%, while the installation cost may be 91.5% less than the cost of adding new windows.
