In this article, we will cover some common questions about low emissivity glass such as what is low-emissivity glass, how does a Low-E coating work and where should you specify it?
Levels of emissivity are measured on a scale of 0 to 1; a level of 1 would signify full radiant energy absorption and a level of 0 would signify a material that reflected 100% of energy directed at it.
Emissivity is the amount of radiant energy material absorbs. When it comes to thermal insulation in buildings and projects you do not want the external elements of the construction to absorb the heat from the internal space, you want this radiant heat energy to remain within the internal spaces in order to maintain a constant heat level internally and reduce heat loss to the external environment.
Glass in its natural state has high levels of emissivity, at around 0.89 for standard, uncoated float glass.
Low E Coatings
Low-E coatings, as they are referred to, is the shorthand for Low Emissivity coatings that are applied to most insulated glazed units in modern architecture and construction.
Low Emissivity coatings are applied to glazing units in order to reduce the amount of heat that glazing units absorb and, therefore, emit to the external of a space. These Low-E coatings reflect radiant heat back into the internal spaces, improving the thermal performance of the glass unit.
Building Regulations Part L demand that all insulated glass units must achieve certain thermal performance criteria, depending on the dwelling type, location and size. Specifying Low E Glass helps architects and specifiers to achieve modern performance values.
Although minimal, Low E Coatings do affect the appearance of the glass unit. The visibility will be slightly reduced and the reflectivity increased, making the glass more visible within architectural designs.
Reflection is inversely proportional to emissivity, therefore the lower the emissivity, the higher the reflectivity. Although there is no solution to combat the slight loss of visibility, the glass still has a transparent nature. Ultimately, thermal performance criteria are needed in order to maintain the energy efficiency standards across all building sectors.
At IQ we include Low E Coatings as standard and these are part of our glass specifications for any double or triple glazed unit. This is to ensure we can achieve unrivaled thermal performances in our innovative glazing designs.
Low E Coatings can be used in conjunction with a range of other technical glass solutions, including coloured interlayers, heated glass, and acoustic sound reduction glass. It is particularly important to check with your glazier that a Low E Coating is applied in oversized glazing installations, such as entire walls made of glass or double-height slim framed sliding doors.