When it comes to improving a property’s thermal efficiency, Low-E glass stands out as an excellent addition. This specialized glass is designed to reflect heat. This significantly reduces energy consumption while offering year-round comfort.
In this guide, you’ll learn exactly what Low-E glass is, the science behind it, the different types that suit various climates, and how installing it translates to energy savings and improved comfort levels in your home.
Key Takeaways
- Low-E glass panes are covered in a thin, almost transparent coating that controls and regulates the heat they absorb and re-radiate.
- Low-E coatings come in different types tailored to climate needs—passive for retaining heat in colder areas and solar control for reflecting heat in warmer regions.
- The efficiency of low-E coatings is measured by ratings like SHGC, VT, and U-factor for optimal thermal performance.
- While low-E glass windows have higher upfront costs, they lead to significant energy savings of 30%-40% time.
Understanding Low-E Glass and Its Energy-Efficient Properties
Low-E glass panes are covered in very thin, transparent coatings called Low-Emissivity Coatings (Low-E coatings). This advanced material serves as a shield against energy loss. Its role in maintaining comfortable indoor temperatures while reducing energy bills is nothing short of extraordinary.
So, how exactly do low-E coatings ensure thermal insulation, contribute to a building’s energy efficiency, and control light and heat transfer? Let’s find out!
What Is Emissivity?
As already mentioned, the term Low-E comes from Low-Emissivity. So, what does emissivity mean?
Let’s start our discussion from a different angle, not by sharing the definition of this term.
All objects that surround us at temperatures above zero emit something called thermal radiation. Here’s an excellent example that illustrates thermal radiation – the Sun transfers heat to the Earth primarily through thermal radiation, which passes through the atmosphere and reaches the surface where it is reflected or absorbed.
Well, emissivity has everything to do with thermal radiation because it represents an object’s capacity to emit energy as thermal radiation. As such, the emissivity of a surface is usually measured on a scale ranging 0.0-1.0, the former being a perfect reflector and the latter being a perfect emitter.
What Does Emissivity Have to Do with Windows?
So, how does this apply to windows? Easy! Like any other object, glass absorbs energy and then re-radiates it. The emissivity of a standard untreated glass surface is 0.8 or higher, which means that it can:
- absorb heat and reradiate it into your home, which can be catastrophic during hot summers
- absorb heat from objects inside the home and emit the heat outside, which can significantly impact indoor temperatures during the winter.
And that’s where low-E coatings come into question. These thin, almost invisible layers added to the glass help the window surface control and regulate the heat it absorbs and re-radiate.
So, during the winter, when the window absorbs indoor heat and tries to emit it outside, the low-E coating will prevent this from happening by reflecting it back inside, thus retaining interior heat energy effectively. During the summer, when the window absorbs heat from the outside and tries to re-radiate it inside your house, the low-E coating prevents this.
By doing this, low-E glass not only keeps your home warm or cold depending on the season but also:
- doesn’t sacrifice visible light transmittance (natural light) and doesn’t obstruct views
- controls and reduces UV and infrared radiation, which can cause damage to the furniture and discolor the wall coverings or other objects in your house.
However, there’s one major thing to consider – not all low-E coatings are the same. They are created for different climates, so it’s crucial to choose the one that suits your home needs. You’ll soon learn why.
Varieties of Low E Coatings
Depending on where you live and the region’s climate, you’ll want your house as warm as possible during the winter or as cold as possible during the summer, right? But how is it possible? Well, there are two low-E coatings designed for different climates:
- Passive low-E coatings: these are excellent for colder climates because they keep solar heat in rather than reflecting it back out. Passive low-E coatings are added to surfaces 3 and/or 4 (see below for more details about glass pane surfaces)
- Solar control low-E coatings: these are excellent for warm, sunny climates because they reflect solar heat and keep your home cold. Solar control low-E coatings are added to surface 2 of a glass pane.
Glass Surfaces
Let’s turn now to the surfaces we’ve mentioned above. When a window has two glass panes separated by insulated spacers, it becomes an insulated glass unit (ICU). As such, window panes have four surfaces:
- 1st Surface: The outside-facing surface of the exterior pane
- 2nd Surface: The inside-facing surface of the exterior pane
- 3rd Surface: The outside-facing surface of the interior pane
- 4th Surface: The inside-facing surface of the interior pane
Low-E coatings can be added to any of these surfaces.
Low-E Glass Production
Low-E glass is produced using two methods: the pyrolytic method and the Magnetron Sputter Vacuum Deposition (MSVD) method.
The first method implies applying the coating to the glass ribbon while it is produced. The coating blends with the hot glass surface, ensuring a strong bond, which is why it’s called a “hard coat.”
The MSVD method implies applying the coating off-line to pre-cut glass. This is done in a vacuum chamber at room temperature.
Low-E Coatings and Energy Efficiency Ratings
Energy efficiency ratings serve as a guide in choosing the ideal Low-E glass that suits your needs, leading you toward optimum performance. These ratings are the benchmarks that quantify how well a window can resist unwanted heat gain or loss and how much natural light it allows inside.
Comprehending these metrics paves the way to harnessing the full potential of a low-E glass in your residential or commercial space.
Solar Heat Gain Coefficient
The solar heat gain coefficient (SHGC) is a crucial metric when rating how energy-efficient a window is. It measures how much solar heat enters a house through the window. SHGC is measured between 0 and 1 – the lower the rating, the less heat enters through a particular window.
Windows generally have a SHGC between 0.25 and 0.8. However, it’s not a one-size-fits-all situation. Why so? If you live in Northern Canada, for instance, you need windows with a higher SHGC to maximize solar heat gain and reduce heating costs. If you live in a region with a hot climate, you need windows with a lower SHGC to reduce cooling costs.
As such, low-E coatings can affect a window’s SHGC. For example, solar control low-E coatings significantly impact a window’s solar heat gain coefficient by reflecting the sun’s short-wave infrared radiation. This way, they mitigate heat transfer through the window.
Visible Transmittance
Visible light transmittance (VT) quantifies the amount of daylight that passes through a window, which translates into limiting the amount of artificial light you’ll use. VT is usually rated 0-1 – the higher the number, the more natural light you’ll get.
Although it adds a bit of tint, low-E coatings do not affect VT too much, which is an excellent compromise between reflecting solar radiation and having a good VT.
U-Factor
When it comes to superior insulation, the U-factor is a critical indicator. This value measures the rate of heat transfer through a window. Consequently, it also measures how well-insulated the window is.
The U-factor is measured between 0.20-1.20. The lower this number is, the better the insulation.
Low-E glass excels at reducing the U-factor. This characteristic enhances the thermal performance of energy-efficient windows, forming a robust barrier against external temperature variations.
The Impact of Low-E Glass on Home and Building Comfort
By reflecting radiant heat, low-E glass boosts any window’s thermal efficiency, playing a crucial role in maintaining steady indoor temperatures all year round.
Whether it’s warding off the winter chill or deflecting the summer heat, low-E glass helps create an oasis of comfort, minimizing the need for additional heating or cooling.
While invigorating during a pleasant spring day, sun rays can be harsh on interior materials, causing fading and deterioration over time. Low-E glass protects the interior by decreasing ultraviolet light transmission. This way, installing low-E glass equals safeguarding your furnishings, flooring, and artwork from the silent ravages of the sun.
Low-E glass offers several benefits:
- They maintain the aesthetic integrity of your interior materials.
- They filter out damaging UV and infrared light.
- They ensure that your space remains bright, welcoming, and energy efficient.
- They strike a sophisticated balance between protection and illumination, enhancing the comfort and appeal of any space.
Cost-Effectiveness and Energy Savings with Low-E Windows
The true worth of low-E glass is evident in its cost-effectiveness and the substantial energy savings it offers. By keeping interior temperatures consistent, low-E glass windows reduce the demand for heating and air conditioning, leading to significant savings on energy bills. Switching to double-pane energy-efficient windows can reduce energy use by 30-40%.
Furthermore, low-E glass protects your property from damage caused by UV light, which translates into additional savings.
Nonetheless, you should definitely consider this aspect when choosing your windows. Ultimately, it all depends on your budget.
Installing a low-E coating on existing glazing usually costs around $10-$25 per square meter. This can end up being quite expensive if the coatings are added to all windows and on multiple surfaces. However, the energy savings over time can significantly outweigh the initial outlay.
Design Flexibility with Low-E Glass Options
Low-E glass not only excels in terms of energy-efficient properties but also offers remarkable design flexibility. Architects and designers can utilize low-E glass in a variety of architectural features, including:
- Windows
- Curtain walls
- Window walls
- Patio doors
- Roofs
- Skylights
This allows them to meet diverse environmental and aesthetic requirements.
Tinted vs. Low-E Glass
Window tint is also known as window film. Just like low-E coatings, window tint is a thin layer added to the glass panes. Both low-E and tinted windows can block UV rays and infrared light. The biggest difference is that tinted windows significantly impact visual transmittance (VT). So, if we’re discussing a bedroom or living room window, you probably don’t want tinted windows because you’ll have little natural light.
Another difference is that low-E glass has better insulating properties than tinted glass since the tinting absorbs sunlight, and the glass can heat up quite fast if it’s hot outside.
Why Are Magic Windows and Doors So Energy-Efficient?
You’ve probably already heard that Magic windows are highly energy-efficient and tailored specifically for the GTA weather. If you haven’t… Well, you’re about to find out!
Our double-pane windows feature an Insulated Glass Unit (IGU) formed by two glass panes. They have a 1-inch warm edge spacer that expands and contracts at the same rate as our glass unit. As such, this allows us to inject twice as much argon gas compared to other window manufacturers, which significantly improves our windows’ energy efficiency, soundproofing, and insulation.
In addition, Magic windows can be equipped with low-E glass coatings and our Thermal Blinds, which act like a third pane of glass, thus exponentially increasing any window unit’s energy-efficient properties.
As such, our windows have the followin genergy ratings:
- U-factor: 0.26-0.30; with our retractable screens and blinds: 0.17-0.30
- SHGC: 0.17 – 0.48
- VT: 0.36 – 0.53
Book a Free Consultation with Magic!
In the journey to a more energy-efficient and comfortable living environment, low-E glass has proven to be an invaluable ally! However, beyond the science behind low-E glass and its link to energy efficiency metrics, one must personalize its application to the region’s climate.
That’s where Magic can help you! Since we formulate our own glass units, we specialize in providing completely unique products that meet specific solar and energy-control needs. As such, we can make our products suit different regions and climates and take into consideration needs specific to your house structure and design.
As such, if you’re looking for replacement windows with low-E glass to maximize your house’s energy efficiency, reach out today to book a free, no-hassle consultation! Magic representatives are looking forward to hearing from you!
Frequently Asked Questions
What is low-E glass, and how does it contribute to energy efficiency?
Low-E glass, or low emissivity glass, contributes to energy efficiency by reflecting heat energy with its microscopically thin coating, reducing energy loss through windows by approximately 35%. This innovative feature acts like a thermos, maintaining desired interior temperatures and enhancing the insulating properties of windows.
Can low-E glass help reduce energy bills, and if so, by how much?
Yes, low-E glass can reduce energy bills significantly. Installing low-E coatings can reduce energy usage by up to 40%.
Are there different types of low-E coatings, and how do I choose the right one?
To choose the right low-E coating, consider your regional climate and energy performance needs. Passive low-E coatings are suitable for cold climates, while solar control low-E coatings are ideal for hot climates.
What are the potential drawbacks of low-E glass?
The potential drawbacks of low-E glass include a slightly altered view, the need for careful installation, and a higher initial cost. However, these drawbacks are minor compared to the benefits of improved energy efficiency, comfort, and protection of interior materials.
How does the placement of low-E coatings affect the performance of insulated glass units?
Proper placement of low-E coatings significantly impacts a window’s thermal performance and solar energy transmission. Solar control low-E coatings are applied to the 2nd surface of the Insulating Glass Unit, while passive low-E coatings are applied to the 3rd or 4th surfaces.