Efficient Window Options
Heating and air-conditioning systems place a heavy load on energy usage in buildings, but that load can be reduced with lighting controls and energy-efficient window technologies. Start with window films if youâ€™re looking to control the sunâ€™s heat, says Jim Mannix, commercial markets manager for energy conservation in the Renewable Energy Division of 3M, St. Paul, MN.
|Photo: Eneclium Technologies |
Goshow Architects, in New York City, used efficient window options throughout 12,000 square feet of retrofitted office space.
â€œWhen we do an energy analysis, the question is what are the windows bringing in and what we can keep out, and whatâ€™s the impact on the HVAC system,â€ explains Mannix. â€œIf you have a wall of glass facing West at two oâ€™clock in the afternoon, thereâ€™s a lot of sun beating down on those windows, and we can reduce as much as 75% of the solar load.â€
A reduction in solar load can have a substantial impact on cooling costs, as was the case with a project that installed 3M Sun Control Window Film Neutral 35, on approximately 11,000 windows in two office towers. The buildingâ€™s management reported savings of 155,000 kWh per month and a payback period of less than eight months.
â€œItâ€™s not just kilowatt-hours,â€ adds Mannix. â€œItâ€™s the fact that so many utilities have demand charges based on such things as peak time of use, to curb demand during peak hours. This window film helps reduce the air-conditioning demand when a building is paying a high-dollar value per kilowatt. And there is the possibility of getting an incentive or rebate from those utilities that are struggling to curb the demands.â€
There are a wide variety of films to control heat, and now a new window technology has the ability to reflect window light towards ceilings so occupants benefit from dispersed light that can spread out evenly to illuminate an interior. In the case of BrightShelf, a product from Hunter Douglas Contract Solar Control, Poway, CA, a polished aluminum shelf installed near the top edge of a window reflects light across a ceiling.
LightLouver LLC, Louisville, CO, takes a different approach. The companyâ€™s products look similar to horizontal window blinds, but the reflective slat design redirects all sunlight above a five-degree altitude angle upward onto the ceiling of the daylit space. The redirected light provides ambient lighting and eliminates direct sunlight on work surfaces.
Both the BrightShelf and LightLouver are part of a growing trend to use daylight harvesting as a tool for building efficiency, and when combined with lighting optimization, the savings on a buildingâ€™s lighting costs can be substantial.
â€œThe reduction in [lighting] energy is about 51% on average and sometimes up as much as 70%,â€ says John Poerstel, sales director, Encelium Technologies, Teaneck, NJ.
Lighting systems like Enceliumâ€™s offer fixture level dimming and switching controls coupled with control software to respond dynamically to the changing characteristics of a building.
â€œFor example, you can have a building on a time clock of 6 a.m. to 6 p.m., so in 12 hours lights are off; but when you layer that with an instruction to come on at six oâ€™clock in the morning, unless thereâ€™s nobody there, you can shut down particular quadrants or spaces within the building,â€ says Poerstel. â€œThen, letâ€™s say somebody comes into that area, it can come on, but only to 85%, which is enough to work and do everything you need during these off hours.â€
Enceliumâ€™s technology was recently used by Fran Pinto, FMA, RPA Facilities Manager FDIC, Arlington, VA. The first step to LEED certification for the six-building campus was a pilot with a combination of Enceliumâ€™s automation and replacement of T-12 fluorescents with T-8s.
â€œWe wanted to basically try it out before we invested time and funds in a computer system to run our lives for us,â€ recalls Pinto.
The pilot ran about a month and the facilityâ€™s team gathered data from the occupants with a survey, as well as metering the savings, which were about 50% of the energy consumed by the previous lighting system.
â€œWe have had only positive feedback from the occupants,â€ adds Pinto. â€œAnd, even though the staff was resistant to change, they adapted and realized that lights were going off often and the lights were dimming, and in the IT department they were very happy with that. We took the data and brought it to the senior management, and noted that we could save a substantial amount of energy. And, yes, weâ€™re saving dollars, but itâ€™s more about saving the energy at this point in time. About a year after the approval, we went to GSA and won out to bid Encelium.â€
In November 2010, the GSA announced that it was upgrading the requirement for new federal building construction from LEED Silver to LEED gold certification. The new requirement also applies to substantial renovation projects. For projects funded prior to FY 2010, GSA is requiring LEED Gold prerequisites and requirements when possible after considering budget and schedule constraints. For GSA leased properties, the requirement remains at the LEED Silver certification for new construction lease projects of 10,000 square feet or more.