Low-emissivity (low-e) glasses are critical to making today’s buildings brighter, more energy-efficient and more sustainable. By controlling solar heat gain and promoting daylighting, they help buildings use less energy for temperature control and lighting, while adding the human benefits associated with outdoor views and more pleasant working and living environments.
Here are five tips to help architects, engineers, and contractors understand and explain the differences among low-e glasses and their impact on building performance:
1. E = Emissivity. Emissivity refers to the relative ability of a material’s surface to radiate energy. Low-e glass has a microscopically thin coating that lowers the emissivity of the glass surface and is engineered to transmit energy from the visible light portion of the solar spectrum (between 380 and 780 nanometers), while reflecting energy from ultraviolet light (310 to 380 nanometers), which causes fading, and infrared light (above 780 nanometers), which makes buildings warmer.
2. Think of a thermos. A thermos works by using a silver lining to continuously reflect and maintain the temperature of the drink it contains. Low-e glasses function according to the same principal, using multiple layers of silver or other low-emissivity materials in the coating to keep heat inside a building or prevent it from entering. Similarly, thermoses and insulating glass units (IGUs) are both designed with air spaces that provide a layer of insulation between the inside and outside.
3. More slivers of silver. Low-e coatings incorporate multiple layers of silver (or other low- emissivity materials) to control the transmission and reflection of heat and light. Recent technical advances now enable glass manufacturers to deposit up to three layers of silver on the glass substrate, which has enhanced the solar control capability of low-e glasses without diminishing their ability to transmit light.
4. Passive for insulation. Passive low-e glasses are usually made using the pyrolitic process, which means the coating is applied while the molten glass ribbon is still on the float line. This produces a “hard” coat that is fused to the glass surface and highly durable, but which has a higher emissivity that a solar-control low-e glass. Passive low-e glasses have decent insulating capabilities, but because of the limitations of metal deposition on the float line, they permit more solar infrared energy (heat) to pass through their coatings and become trapped inside the building. Consequently, passive low-e glasses are often the best choice for cold, heating-dominated climates.
5. Solar control to reduce heat gain. Coatings for solar control, low-e glasses are applied to pre-cut sheets of glass in a vacuum chamber at room temperature. This gives glass manufacturers the ability to deposit more sophisticated coatings (with multiple layers of silver) on the glass substrate, which improves solar control of the infrared (heat) portion of the solar spectrum without substantially diminishing the transmittance of visible light. These coatings are the best choice for hot, cooling-dominated (and moderate) climates. The lower emissivity of solar control low-e glasses also provides better insulating values to maintain the interior temperatures.
To learn more about low-e glass and other topics related to designing, specifying and building with glass, visit the PPG Glass Education Center at http://educationcenter.ppg.
Related Stories
| May 8, 2014
Perfecting prefab: 8 tips for healthcare construction projects
Leading AEC firms offer helpful advice for using BIM to pull off prefab for everything from MEP infrastructure to whole bathrooms.
| May 8, 2014
Don’t bother planning for the future - it doesn’t care about you
Though strategic planning has helped many businesses move forward, its time has passed. So says Economist and Author Bill Conerly. SPONSORED CONTENT
| May 8, 2014
Infographic: 4 most common causes of construction site fatalities
In honor of Safety Week, Skanska put together this nifty infographic on how to prevent deadly harm in construction.
| May 8, 2014
Sporting events in style: Infographic showcases novel stadiums of the world
UK precast concrete maker Banagher, which specializes in precast stadia solutions, has assembled a list of the world's top stadiums in terms of architectural and structural design.
| May 7, 2014
Design competition: $900,000 on the line in Las Vegas revitalization challenge
Las Vegas Mayor Carolyn Goodman wants your economic development ideas for remaking four areas within the city, including the Cashman Center and the Las Vegas Medical District.
| May 6, 2014
'Beyond' is artist's cinematic take on 2.5 years of development in the UAE
Seven-minute video offers a time-lapse trip through the built environments of Abu Dhabi and Dubai.
| May 6, 2014
'Ugliest building in New Jersey' finally getting facelift
After a decade of false starts and mishaps, the American Dream mall in the Meadowlands may finally get built.
| May 5, 2014
Toronto residential tower to feature drawer-like facade scheme
Some of the apartments in the new River City development will protrude from the building at different lengths, creating a drawer-like "push-pull" effect.
| May 5, 2014
Tragic wired glass injury makes headlines yet again
In the story, a high school student pushed open a hallway door glazed with wired glass. His arm not only broke the glass, but penetrated it, causing severe injuries. SPONSORED CONTENT