Improving Energy Efficiency And Comfort With Glass Coatings

By Amy Roberts

Energy conserving buildings donate to greater utility cost savings for building proprietors and facility supervisors with possible pass-through to tenants. The developing envelope’s fenestration techniques – its curtain walls, storefront, windows, doorways, skylights, along with other glass and glazing components – provide significant possibility to donate to energy efficiency and savings typically.

Fenestration’s influential effect on a facility’s energy goals have concentrated on improving thermal performance by minimizing conductivity, heat energy transferred through the building envelope. Basically: Keep carefully the cold outside in winter for heating-dominated, northern climate zones. Keep carefully the heat outside in summer for cooling-dominated, southern climate zones. Maintain a reliable, comfortable interior temperature year-round.

Tinted glass coupled with a low-e coating might help achieve an energy-efficient, attractive and economical facility. (Credit: Image by Abstract Photography, Inc.; thanks to EFCO Corp.)

The insulating glass (IG) unit could be the primary solution in every commercial fenestration applications seeking improved thermal performance. An IG unit includes several lites of glass separated by insulating and structurally supportive spacers to make a hermetically sealed cavity that may be filled up with dry air or an inert gas – typically argon. An IG unit’s performance could be further increased with the addition of low-emissivity (low-e) or reflective coatings, tinted glass, and insulating methods. Increasing the real amount of glass lites and cavities, such as for example with triple IG units, can upgrade performance also. speaking

Practically, the ability to boost energy efficiency by reducing fenestration’s conductivity may have arrived at its upper limit. Now, glass and fenestration manufacturers are digging deeper to wring out incremental energy savings by concentrating on radiant heat transfer through solar heat gain optimization. Advanced glass coatings have moved to center stage.


Incident solar radiation includes three types: visible light (VL), infrared (IR), and ultraviolet (UV), the latter which could cause fading of draperies, artwork, furniture, and carpets. In lots of commercial buildings, the perfect energy-conserving glass would let generally in most of the visible part of the solar technology – reducing lighting requirements in the facility – while blocking a lot of the UV radiation and IR heat energy.

The IR solar radiation that’s transmitted through architectural glass is expressed as a fraction between 0 and 1. This fraction is named as a solar heat gain coefficient (SHGC). The low the SHGC is, the less solar technology it transmits. Generally, a minimal SHGC is desirable in warm climates, through south- especially, west- and east-facing fenestration products, and an increased SHGC is desirable in colder regions. For comparison, clear glass registers an SHGC of 0.90 or greater.

Low-e Coatings

Low-e coatings certainly are a relatively recent innovation that has been the premier choice for improving thermal performance by allowing certain wavelengths of solar radiation to feed easier than others. This can help to control solar heat gain in both cold and warm climates. Emissivity is a way of measuring a material’s capability to re-radiate absorbed IR radiation, so low-e indicates an capability to reduce heat absorption. Generally, reflective materials have a minimal emissivity highly, and duller, darker colored materials have a higher emissivity.

Low-e cup includes a invisible nearly, thin coating of steel or metallic-oxide microscopically, such as for example tin or silver oxide. This coating is put on a surface of 1 or even more panes of an IG unit to provide an emissivity only 0.04. This enables for the reflection of around 96% of IR radiation back toward the foundation.

The keeping low-e coatings in a IG unit matters furthermore, based on climate and the power efficiency objective. The IG could be fine-tuned for heating-dominant or cooling-dominant climates by varying the glass surface to that your coating is applied. The glass surfaces are numbered, with #1 representing the surface or “weather” surface. Figure 1 (below) represents a double-pane fenestration product with surfaces from 1 to 4. Similarly, a triple-pane product could have surfaces from 1 to 6.

Figure 1: Double Glazing Illustration (Image thanks to FGIA)

In northern, heating-dominated climates, a low-e coating on the inner surface of the inside pane (#3) or the inside surface (#4) of an IG unit reduces heat loss by reflecting heat back to the interior, while reflecting the HVAC program’s heat power inside back. (Before choosing the #4 surface product, the maker ought to be consulted regarding any special considerations useful.)

In southern climates which are cooling dominated, a low-e coating put on surface #2 reflects or rejects the solar heat back outdoors, lowering solar heat gain and keeping the available room cooler. Some versions can block nearly 80% of the sun’s radiant energy, while transmitting a lot more than 50% of the available sunlight.

Some IG units have low-e coatings on two surfaces. For instance, a triple-pane IG unit with low-e coatings put on the #2 and the #5 surfaces of an IG unit could decrease the thermal performance, as measure at the center-of-glass, by 31% in comparison to a unit with a single-coated lite.

For climates that get cold in winter and hot in the summertime, dual-pane IG units with a silver-based low-e coating on surface #2 could be specified with a coating on the #4 surface to reflect escaping heat back to the area. Spectrally selective low-e coatings – which combine the very best qualities of low-e, tinted and reflective glass – may also be best for mixed climates where both cooling and heating are essential. They help restrict heat energy from sunlight, but allow in a lot of the light. Applying different combinations can provide a broad selection of SHGC between 0.78 and 0.17.


Various kinds of low-e along with other coatings could be combined or put on different IG glass surfaces to attain a targeted performance level.

One combination, recommended for used in cold climates, is coated with a thin microscopically, optically transparent layer of silver that’s sandwiched between layers of anti-reflective metal oxide coatings. A low profile, protective coating is put on ensure durability and longevity.

An obvious low-e coating also permits natural daylighting. (Credit: Image thanks to Edgetech)

Low-e coatings can also have multiple layers. For instance, one version adds a third layer of silver coating, producing a clear coating that blocks more solar radiation even, reflects heat and a higher visible transmittance, which enhances daylighting. This type of combination outperforms tinted glass normally found in warm climates actually.

Another option is usage of laminated glass with anti-reflective coatings on both surfaces #1 and #4, which reduces interior and exterior visible light reflectance to significantly less than 2%, while blocking a lot more than 99% of UV radiation.

Combinations of clear and opaque glass develop a modern architectural style with up-to-date performance. (Credit: Image thanks to YKK AP America)

Perhaps surprisingly, other styles of coatings that may be combined with low-e to increase performance include the ones that can donate to a facility’s energy supply through building integrated photovoltaic applications. Others can lower maintenance costs through coatings that help breakdown organics and pollutants with help from the sun’s Ultra violet rays, helping glass longer remain cleaner for.

For some current applications, a double-pane IG unit with appropriate low-e coatings can meet most building’s energy savings goals. However, attitudes and requirements quickly are changing, and much more efficient products are increasingly being demanded by owners, municipalities and occupants.

As fenestration and cup plays an ever-increasing function in the entire appearance of industrial landscapes, custom-tailored IG units can incorporate various glass types, thicknesses, coatings or tinted substrates to generate buildings which are energy-efficient, attractive and economical. Glass and fenestration producers might help in selecting products suitable for meet a service’s performance uniquely, financial and aesthetic goals.

Roberts is FGIA Director of Canadian and Technical Glass Operations. She oversees the Fenestration and Glazing Industry Alliance (FGIA) Canadian standards and regulatory building/energy codes, plus the Insulating Glass Certification Council/Insulating Glass Manufacturers Alliance (IGCC/IGMA). She’s more than twenty years of industry experience in IG and glass manufacturing, and in both business and residential window production.

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