LoW-E Glass. its types and the effects of its energy efficient

When it comes to windows, the type of glass you choose is a critical consideration. Experts estimate that 70 percent of energy loss occurs in windows and doors, and that 90 percent of window heat loss occurs through the glass. Energy efficiency is important, but the lingo can be very confusing when researching different types of energy-efficient glass.  We’ll explain what the Low-e glass is, why it’s energy efficient, the different types of Low-E coatings and which is best for the area you live in.

Low-e is standard clear glass which has a special coating on one surface of the glass. Low-e refers to low emissivity and this describes the capacity of a surface to radiate heat. Emissivity is measured across a scale from 0 to 1 with 1 representing the highest emissivity.

Low-e glass

The low-e coating is spectrally selective, which means it affects some wave lengths of light but not others. Long wave infrared is the heat produced by our bodies, heaters and the furnishings in a warm room. The transmission of long wave infrared is significantly reduced by the low-e coating. It reflects the amount of energy escaping through the glass keeping the room warmer and reducing the amount of heat required to be generated by the artificial heaters. The energy from the sun is called short wave infrared; a high proportion of energy from the sun will be transmitted straight through the glass.

Low-e coatings provide various performance levels and the glass can be used in a variety of ways including single glazing, laminated glass or double glazed windows.

The benefits of low-e glass

Low-e glass can reduce the amount of heat that is conducted through the glass by around 30% compared to ordinary glass. Low-e glass further improves thermal efficiency by cutting glare and preventing damage interior furnishing caused by ultra-violet rays.

Newer generation low-e often uses laminated and toned glass combinations to provide superior performance over non coated glass. The most comprehensive solution is found by combining a low-e coating with double glazing. Using low-e coating and a suitable frame can stop up to 70% of heat loss and 77% of heat gain when compared to standard 3mm glass.

Tip  

• The lower the emissivity value of the glass, the less heat absorbed and re-radiated through to the colder side.

Hard or soft coat low-e glass

There are two types of low-e glass: hard coat (online) or soft coat (offline). Hard coat low-e glass is made by coating the glass during production with a thin metallic oxide layer, effectively welding it to the glass surface. Soft coat low-e glass, or sputter coating, is applied to glass that has already been formed. The glass enters a vacuum chamber filled with an inert gas which is electrically charged. The electricity combined with the vacuum allows molecules of metal to sputter onto the glass. This process provides the highest level of performance and a nearly invisible coating.

Hard coat low-e glass is the more common variety. It is durable and difficult to scratch, and can be used for single-glazed applications. On the down side, it has higher U-values compared to soft coat low-e glass, and slightly higher haze levels.

Soft coat low-e glass, on the other hand, is less common, and allows more visible light in with less visible haze. Its ultra-low emissivity also gives excellent U-values. The down side of soft coat low-e glass is that it must be used in double glazed windows, and that there can be slight colour variations. Soft coat is less durable than hard coat.

Glass surfaces are conventionally numbered, starting at the outside, with surface #1.

Which side of the glass to coat

The effectiveness of low-e glass is dependent on the direction the coating is facing. For single pane windows it is recommended the low-e coating is always placed on the inside facing surface. Low-e coatings are sensitive to weather and pollutants making it difficult to clean without damaging the surface.

In double glazed windows low-e glass can be specified on a particular side of the glass depending on what you want to achieve. For warm climates where summer heat reduction is a priority, the coating should be on the inside facing surface of the outside pane (surface #2). This will minimise heat coming into the home by absorbing solar radiation and reflecting it back outside.

In cold climates where retention of heat is a priority, the coating works best by facing outwards on the inside pane (surface #3). The coating will work by absorbing inside heat and reradiating it back into the room.

Common problems

Low-e glass reduces solar gain in winter as well as summer. For this reason it is not recommended for solar control in colder climates when the winter sun provides valuable natural heating. It is more beneficial to use low-e glass with double glazing to only reduce winter heat loss.

Which Type of Low-E Coating Glass is Best for My Climate?

Are you unsure which type of Low-E glass is best for you? Before you decide, it is important to consider your area’s climate:

• If you live in an extremely cold climate, the hard-coat Low-E glass may be an option for you, because it allows some of the sun’s short-wave infrared energy to pass through the glass. This helps to heat your home in the winter and allows the glass to reflect the interior long-wave heat energy back inside.
• However, if you live in a cold to hot climate, which covers nearly all of the United States, the soft-coat Low-E glass is best, since it offers better UV protection and has a better overall U-value. The soft-coat Low-E coating also reflects the warm and cool air back into your room instead of allowing it to leak outside.

When you’re trying to decide which Low-E is best for your home, it’s also very important to consider which type of glass would work best. Low-E coatings play a pivotal role in the performance of your windows, can save you money on energy costs and can drastically reduce fading to furniture and décor by blocking UV rays. Hanjin Glass are made with a variety of high performance, energy-efficient glass options that can meet your energy performance and budgetary needs. We make insulated window glass used hard-cost Low-E glass,double silver Low-Glass and Triple Silver Low-E glass. Our Low-E glass can provide the highest level of year-round comfort and energy savings.