Insulated Glass and Low-E Glass: Key Differences Explained

Key Takeaways

• Insulated glass (IG) is a multi-pane window system designed to reduce heat transfer and improve energy efficiency.
• Low-E (Low Emissivity) glass is a type of coated glass that reflects infrared and UV rays, keeping interiors warmer in winter and cooler in summer.
• While insulated glass targets thermal insulation through structure and gas fills, Low-E glass enhances that performance by controlling solar radiation.
• The combined use of IG and Low-E coatings is common in Canadian homes for achieving maximum comfort and efficiency.
• DraftLOCK technology from Canadian Choice Windows & Doors™ integrates both elements for climate-optimized performance.

Canadian homeowners often wonder whether insulated glass or Low-E glass makes the bigger difference in comfort and energy savings. The truth is: both matter — and they work best together. Here’s a clear, no-pressure breakdown to help you understand how each option works, and how to choose what’s right for your home and climate.

What is the difference between insulated glass and Low-E glass?

Understanding Insulated Glass (IG)

Insulated glass, often referred to as insulated glass units (IGUs), is composed of two or more panes of glass separated by a spacer and sealed to form a single unit. The space between the panes is typically filled with inert gases, such as argon or krypton, which are poor conductors of heat. This multi-pane structure is designed to minimize heat transfer between the interior and exterior environments.

Structure of Insulated Glass:

• Outer and inner panes are usually made from float glass or tempered glass.
• Spacer system: Made of metal or composite material, it keeps panes at a fixed distance.
• Gas fill: Argon or krypton gases increase thermal resistance.
• Seals: Primary and secondary seals prevent moisture ingress and gas leakage.

This system significantly reduces energy loss and helps stabilize indoor temperatures — essential in regions like Ontario, where winters can be harsh and prolonged.

What this means for your home is simple: fewer drafts, more stable temperatures, and lower heating bills — primarily through long winters.

Understanding Low-E Glass

Low-E glass features a nearly invisible coating that helps retain warmth during winter and reduce unwanted heat in summer — a simple upgrade that makes a noticeable difference in comfort.

Structure of Low-E Glass:

• Glass substrate: Standard float glass
• Low-E coating: A thin layer applied to one side of the glass (usually the inner surface of the outer pane in IGUs)
• Types of coatings:
  • Hard coat (pyrolytic): Durable, applied during manufacturing, good for colder climates.
  • Soft coat (sputtered): More energy-efficient, applied after the glass is formed, better for high-performance applications.

These coatings reflect heat into the room during winter and reflect solar heat away in summer. Additionally, Low-E glass filters up to 99% of UV rays, helping protect interior furnishings from fading.

For homeowners, the benefit is noticeable: rooms stay brighter without overheating, furniture and flooring last longer, and your home feels comfortable year-round.

Insulated Glass and Low-E Glass

Everyday Use Cases for Each Glass Type

Where Insulated Glass is Used:

• In residential windows and patio doors , where improved insulation is needed.
• In office buildings, especially in colder provinces like Alberta and Manitoba .
• In double or triple-glazed windows designed to enhance energy performance.

Where Low-E Glass is Used:

• In south-facing windows, where solar heat gain can become excessive.
• In urban buildings, where UV protection for interior fabrics and finishes is essential.

Can You Use Both Together?

Absolutely. In fact, most modern high-performance windows feature Low-E coatings within IGU setups. When combined, they address both conduction and radiation heat transfer. This pairing has become standard in Canadian window manufacturing, including with Canadian Choice Windows’ DraftLOCK™ system , which integrates triple-glazed IGUs filled with argon and advanced Low-E coatings tailored for local climates.

Industry-Backed Insights

At Canadian Choice Windows & Doors™, we guide homeowners through these choices based on their home, budget, and climate — no guesswork, no pressure. Whether you’re upgrading a single room or planning a complete retrofit, the proper glass setup should fit the way you live, not the other way around.

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In the words of Helen Sin, Consumer Success Manager at Canadian Choice Windows :
"Customers often think they have to choose between insulated and Low-E glass, but they work best together. It’s all about the balance between heat retention and solar control — especially in places like Ottawa or Mississauga."

Is Low-E glass worth the investment for energy-conscious homeowners?

Measuring the Return on Investment (ROI)

In Canadian homes, these savings translate directly to reduced utility bills. A study by Natural Resources Canada found that low-E coatings, combined with argon-filled IGUs, can save homeowners up to $400 annually in heating and cooling costs, depending on the home's size, window placement, and regional weather conditions.

Long-Term Value Over Initial Cost

The average premium for Low-E glass ranges between 10% and 15% more than that of standard clear glass. But consider this:

• Windows typically last 20 to 25 years
• Most Canadian homes require multiple windows to be upgraded at once
• Many homeowners qualify for rebates (discussed below)

Over the window's lifespan, the long-term energy savings typically exceed the initial investment — especially when combined with modern window frames and weatherproof installation.

Seasonal Performance: Winter vs Summer

In colder seasons, Low-E coatings reflect indoor heat into the room, reducing heating needs. In summer, they minimize solar heat gain, lowering cooling costs. This dual-purpose performance is what makes Low-E particularly relevant in Canadian provinces like Ontario, where temperatures can swing dramatically between seasons.

• Winter benefit: Reduces thermal loss by up to 70% vs single-pane glass.
• Summer benefit: Reduces solar heat gain by 50% or more, depending on window orientation and coating type.

Your local climate aren’t one-size-fits-all. Homes in the Prairies need maximum winter insulation, while coastal BC benefits from solar control and moisture resistance. Low-E and insulated glass help balance these differences, delivering reliable comfort wherever you live.

Can you combine insulated glass and Low-E coatings in one window?

The Layered Approach to Window Performance

There’s a common misconception that Low-E glass and insulated glass are separate product types. In reality, the two are most potent when combined.

Modern IGUs almost always include Low-E coatings as a standard or optional feature — especially in Canadian-built windows engineered for four-season performance.

"It’s not a choice between Low-E and IG — you get the best of both with DraftLOCK," says Tony Wong, Project Manager at Canadian Choice Windows . "These technologies are meant to work together, not compete."

How the Integration Works: Specification Table

These layers work in tandem to manage both conduction and radiation, the two dominant forms of heat transfer.

Real-World Benefits of Combining IG + Low-E

By integrating Low-E coatings within insulated glass units, homeowners benefit from:

• Superior thermal resistance (U-factors as low as 0.15)
• Reduced heat loss in winter and solar gain in summer
• Lower energy bills across all seasons
• Enhanced protection against UV fading
• Reduced condensation from warmer inner glass surfaces

This integration is not just technical — it’s practical. In Canadian homes, particularly in high-efficiency builds or EnerGuide-rated retrofits, this combination is now standard.

Addressing Misconceptions

Some homeowners worry:

• "If I choose Low-E, will it ruin my view or make the glass darker?"
• "Is it more fragile or prone to fogging than IGUs alone?"

The answer is no. When applied correctly (as it is in DraftLOCK systems):

• You won’t notice the coating — only the comfort.
• It’s applied to the inner face of an IGU, protecting it from damage
• There is no added risk of condensation or seal failure

What should Canadian homeowners consider when selecting between different types of glass?

Window upgrades aren’t one-size-fits-all. The best option depends on where you live, what your house needs, and how you prioritize comfort, cost, and environmental impact.

Here’s a step-by-step approach to selecting the right glass type for your home:

Step 1: Assess Your Region and Climate

• Cold-prone provinces like Alberta, Manitoba, and Ontario benefit most from triple-pane IGUs with Low-E coatings.
• Milder climates, such as those found in coastal BC, may find double-pane Low-E windows sufficient, especially when combined with energy-efficient frames.
• Use this Government of Canada map to check your climate zone and ENERGY STAR® requirements: NRCan Climate Zone Map.

Step 2: Understand Your Home Type

• Older homes (built before 1990) are likely to have single-pane or early double-pane windows. Upgrading to IGUs with Low-E offers the most dramatic gains.
• Newer builds may already feature IGUs but might lack premium coatings — consider upgrading to soft-coat Low-E if sun control or fading is an issue.
• Urban condos and multi-residential units often focus on UV protection and noise reduction — Low-E glass in laminated form can help.

Step 3: Evaluate Sun Exposure

• South- and west-facing windows experience more solar gain. Low-E coatings help reflect that excess heat in summer.
• North-facing windows lose heat in winter. Insulated, triple-glazed windows with Low-E coatings are most effective in this situation.

Step 4: Check Rebate Eligibility

Federal and provincial programs can offset costs significantly:

• Canada Greener Homes Initiative offers up to $5,000 in rebates for window and door upgrades
• Enbridge HER+ (Ontario) and regional utility programs also apply to ENERGY STAR-rated Low-E IGUs
• Always verify current offers at Canada Greener Homes Grant

Step 5: Define Your Main Goals

• Comfort-focused? Opt for triple-pane IG + dual Low-E for stable year-round indoor temperatures.
• Eco-conscious? Prioritize soft-coat Low-E with high SHGC ratings and ENERGY STAR certification.
• Budget-driven? A double-pane IG with single Low-E is still a significant improvement over older windows.

What’s the final takeaway on Low-E and insulated glass for your home?

Choosing the Right Window Glass

Decision by Scenario

• Tight budget? Upgrade to double-pane IG with a hard-coat Low-E.
• Mid-range remodel? Choose triple-pane IG + single soft-coat Low-E.
• Full energy retrofit? Go with triple-pane, argon-filled IGUs and dual Low-E coatings.

Whether you’re replacing a few windows or planning a full retrofit, always work with a supplier that understands Canadian conditions. Our DraftLOCK™ windows combine insulated glass and Low-E coatings to deliver proven performance in your local climate — from freezing winters to humid summers.

"There’s no single answer, but one rule holds: don’t skip the Low-E. It’s the single biggest leap you can take in energy performance for glass," says Helen Sin.

For over 40 years, Canadian Choice Windows & Doors™ has designed and built windows specifically for Canadian conditions — from the inside out. Our products are locally made, tested across extreme temperatures, and supported by teams who understand the unique needs of Canadian homes.