Close a Window, Open a Door
- By Janet Wiens
- October 1st, 2010
They have been around for centuries — providing protection while they’re slammed, bumped, and abused as much or more than any product in or feature of a building. Welcome to the world of windows and doors, where little appreciation is given but people are quick to complain when they don’t work.
The technology and materials associated with windows and doors is certainly not as cutting-edge as advancements in a building’s HVAC, security, or audio-visual systems. While perhaps unheralded by those outside the building industry, recent improvements in window and door products are critical to maximizing energy efficiency and creating a sustainable environment.
Windows to the World
“I believe that ‘cutting-edge’ refers to the push for energy efficiency when it comes to windows and doors,” said Terry Zeimetz, commercial marketing manager for Pella Corp. “The concern for sustainability, maximizing energy efficiency, and reducing costs are the major factors behind advancements in materials or the re-engineering of existing products in these markets.”
Windows are manufactured from a relatively small group of materials: steel, vinyl, fiberglass, aluminum, wood, or wood with an aluminum frame. Each of these materials has its advantages and disadvantages. Evaluating which type of window to use must be based on energy efficiency, sustainability, cost, durability, maintenance, and aesthetics.
“The two most important components are the frame and the glass,” said Zeimetz. “Improvements in the coatings for glass and in thermal barriers for the frames are cutting-edge in many ways.”
Minimizing the transfer of heat through the glass — heat out in winter and heat in during the summer — is the main goal. Coatings have gone from one layer of microscopic silver to address this issue to two or even a triple layer of silver coating. According to Zeimetz, most college and university facility professionals select glass with a double layer, and an increasing number are specifying a triple layer.
“My experience is that aluminum windows with a thermal break or aluminum-clad wood windows are the top choices for higher education buildings,” Zeimetz said. “The other options are obviously used, but these two are currently the most popular from my perspective.”
Mike Turner, vice president of marketing for YKK AP America, agreed with Zeimetz that sustainability and energy efficiency are two forces driving advancements. “Manufacturers are offering more products with thermal barriers and are re-engineering existing products to meet market demand,” he said. “Products should be selected based on their integration with HVAC systems and other insulating products, such as exterior materials. The insulation in the entire building envelope must work together to maximize efficiency.”
In looking at the building envelope there are at least three main categories to consider, according to Turner: entrance doors, curtain walls, and operable windows. A façade requires many different components, and it is necessary to calculate the potential energy savings for products individually and as a whole.
“Facility professionals should select products with the lowest U value because this means that its insulation properties are better,” Turner said. “Evaluate products on an apple-to-apple basis. Compare the frames and glass separately and then evaluate the entire package. Consider condensation resistance, wind and dead loads, structural performance, and water resistance.”
Turner reiterates the importance of products that work together. “[We offer a line that] includes a sunshade, light shelf, and a heavy-duty architectural-grade window system that includes a triple glazing feature with integral blinds. The combination of the sunshade with the light shelf offers very positive results when it comes to energy efficiency. Other companies also offer products that work together to maximize performance while reducing energy costs.”
According to Turner, energy efficiency will become even more important in the next three years. He points to the projected release of the International Green Construction Code, scheduled for release in 2011, and the goal of constructing net-zero buildings as forces that will continue to drive improvements.
Doors Go Green
Doors constitute a small portion of a facility’s surface area. However, the importance of the role played by exterior doors in the overall energy efficiency of a building cannot be overlooked. As with windows, care should be taken to specify doors and door components with intent to limit thermal exchange.
While there are not specifications directly relating to commercial exterior doors, the more general recommendations for green qualities do give guidance with regard to: recycled content in building materials, optimized energy performance, materials that are processed regionally, the adhesives and sealants and the odors and gasses that they emit, and natural lighting.
“In the past several years, we have received more requests for doors manufactured from recycled components, and the industry has responded to this desire,” said Walt Lutzke, marketing promotion coordinator for Tubelite. “The availability of recycled products has improved substantially.”
A line of Tubelite’s door products, as well as other manufacturers’, are only one of the many choices that are available. These doors include thermal barriers that are manufactured using a high recycled content (a minimum of 80 percent recycled aluminum) billet composition that features energy-friendly finishes and an l-shaped thermal strut reinforced with 25 percent nylon fiber.
Facility professionals must thoroughly evaluate the amount of use a door will receive in order to select the best option. “Durability is critical,” says Lutzke. “Investing more money in an exterior door that is thicker, has an efficient thermal barrier, and that has thicker glass with triple glazing will more than pay for itself in the long run.”
Lutzke strongly encourages the retrofitting of existing doors, including replacing worn weatherstripping and sweeps at the bottom. “A great door won’t perform as well as it can unless it is properly maintained. You must invest in maintenance to protect your initial investment.”