NATIONAL REPORT—For hotels, motels, and resorts, insufficiently insulated windows can be a serious problem that literally sends profits “out the window” in the form of excessive heating and cooling bills.
When it is warm inside the hotel and cold outside, window panes will transfer heat by thermal conduction so additional heating is required to keep guests comfortable, and a similar process is involved when it is hot outside and cool inside. Air leakage through window seals that crack over time worsens the problem, particularly in harsh weather.
While single pane windows transfer the most heating and cooling, even dual pane windows may be insufficient to tame high utility costs.
Now hospitality managers are looking to an innovative approach that adds an inner insulating window to existing windows. This can reduce heat loss by 77 percent or more for single paned windows, and heating/cooling bills by up to 30 percent, while stopping air infiltration for further energy savings and greater comfort.
Adding the inner window, in fact, provides an additional layer of insulation with better insulation values than the best double pane windows. The same practice will also substantially reduce unwanted external street noise to provide guests a better night’s sleep and a more peaceful environment.
Cutting Heating & Cooling Cost
Two factors are vital to keeping hotel heating and cooling costs from escalating: the window’s basic insulation value and preventing air infiltration through and around the window’s seals.
Window Insulation Value
The window’s basic insulation value is largely a factor of the air pockets or bubbles that adhere to panes of glass. These serve as insulative barriers to the transfer of heating or cooling by thermal conduction.
“Air pockets or bubbles ‘adhere’ to glass, which is the major reason glass has any insulating value,” explains Randy Brown, President of Soundproof Windows, a national manufacturer of window energy efficiency and soundproofing products. “The more such air bubbles adhere to the glass, the better the insulation.”
In practice, with a single pane of glass there are two air bubbles, one on each side of the pane. With dual pane units, there are three bubbles, one on each side of the panes and one between them.
However, according to Brown, with a second window acting as an insulating window, there are five bubbles when used with a single pane window if the air space is more than 1 inch.
As an example, an air space of 2 to 4 inches usually separates the existing window and the Soundproof Window, which serves as a “second insulative window” that can be installed easily in front of the existing window. The product is designed specifically to match and function like the original window, no matter its design or whether it opens or closes.
In terms of measuring energy efficiency, the R value of a window indicates its resistance to transferring heat. Better windows have higher R values.
Adding such a “second window” can actually increase the hotel window’s insulation R value by 2.5 or more, dramatically reducing heat loss. This reduces window heat loss by about 77 percent for single pane windows. It can substantially improve insulation values for dual pane windows as well.
A window with a single pane of glass, for instance, has an R value of 1.15. One with a dual pane of glass, with ½” air space, has an R value of 1.81. However, an existing single pane window with a “second insulative window” would have an R value of 3.84; and a double pane window, an R value of 4.40.
Preventing Air Infiltration
Air infiltration due to leaky window seals often causes cold drafts and temperature differences within the hotel room. To compensate for these cold drafts, guests or hotel management often set the thermostat higher.
Due to wind and temperature cycling, particularly in extreme climates, most window seals typically start leaking significantly within a few years.
To prevent such air infiltration, however, Soundproof Windows frame seals are held under a constant tension, using custom made tempered stainless-steel springs that actively squeeze down on the window. This means the window seal is flexible, constant and always working.
When used in combination with existing windows, in fact, the second window seals effectively eliminate any cold drafts or air infiltration, further increasing energy savings. In terms of reliability, such seals are guaranteed for a 50-year lifespan.
Silencing External Noise
The same approach of adding an inner second window can also do double duty for hotels by preventing loud external noise sources, such as traffic, honking, or pool play, from penetrating the windows to disturb guests’ sleep or peace of mind.
The inner window essentially reduces noise from entering on three fronts: the type of materials used to make the pane, the ideal air space between original window and insert, and improved, long-lasting seals. The combination can reduce external noise by up to 95 percent.
“The first noise barrier is laminated glass, which dampens sound vibration much like a finger on a wine glass stops it from ringing when struck,” explains Brown. “An inner PVB layer of plastic further dampens sound vibrations.”
Air space of 2 to 4 inches between the existing window and the Soundproof Window also significantly improves noise reduction because it isolates the window frame from external sound vibrations.
The company’s spring-loaded seals in the second window frame comprise a third sound barrier. “This puts a constant squeeze on the glass panels, which prevents sound leaks and helps to stop noise from vibrating through the glass,” explains Brown.
When the 11-story, 144-room Four Diamond Hotel in downtown Houston protected many its windows from external noise with Soundproof Windows, the energy savings were substantial.
A detailed one-year study showed the hotel saved $2.11 in energy savings per occupied room night. This amounted to 15.7 percent per occupied room night for an ROI of 22.6 percent over 4.37 years. The hotel has electric air-conditioning, natural gas heating and dual pane windows.
Whether hotel owners and managers seek to significantly reduce heating-cooling related energy costs or protect their customers from stressful external noise intrusion, economically soundproofing existing windows, rather than replacing them, is now an option.