Low-E Window Film vs Low-E Windows – Which Offers Better Energy Savings?

As climate change continues to heat the world, economic challenges rise for the average homeowner, and the problem of energy poverty grows worldwide. In response, the building industry must find simple and affordable solutions to regulate temperatures inside homes and buildings, reduce energy consumption, conserve resources and decrease cost expenditures. Windows are a significant source of heat loss and solar gain in structures but also represent “low-hanging fruit” in developing a solution for this ever-growing problem.  

One of the most effective technologies to combat heat transfer is low-emissivity (low-E) coatings, which help regulate indoor temperature, conserve energy and save money. These coatings can be integrated into newly manufactured windows or applied to existing ones as an energy retrofit. This article compares low-E windows and low-E coatings, helping you decide which option fits your budget and needs.

New Windows with Low-E Coatings

Low-E windows are manufactured with a microscopically thin, virtually invisible metal or metallic oxide coating on the glass surface. These coatings are designed to reflect infrared heat (keeping heat inside during winter and outside during summer) while still allowing visible light to pass through. According to Natural Resources Canada, “Low-E coatings can reduce heat loss in the winter and heat gain in the summer by up to 50 percent. This is beneficial as it helps to maintain a comfortable room temperature year-round, reduces the load on a home’s heating, ventilating, and air-conditioning (HVAC) system, and saves on energy bills.” For a deeper dive into the particulars of windows with this technology, check out our article The Pros and Cons of Low-E Glass.

A Cost Comparison

While the cost of windows varies based on factors such as region, supplier, material and size, low-E windows come with a higher price tag across the board. Where a standard double-pane window in a vinyl frame of average size (approx. 36″ x 48″) might cost $500–700 installed, the same size window but with low-E glass can cost about $600–800 installed. On average, the cost difference between the two window types is about 15 percent.

Energy Savings and ROI

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Estimates suggest replacing old, non-efficient windows with ENERGY STAR–rated low-E windows can save up to 33 percent on heating and cooling costs. Therefore, if you installed 10 low-E windows for an upfront cost of $5,000 and save $250 annually on energy bills, the payback period is about 20 years. This figure just represents cost and doesn’t include the added benefits like improved comfort, reduced fading of interiors, noise reduction and enhanced safety and security of the glass, all of which contribute to long-term value. 

Retrofit Existing Windows with Low-E Films 

For buildings with windows in good condition, retrofitting low-E films offers an affordable and efficient alternative to reducing heat transfer and saving on energy costs. Various window film options are available, which can be applied to the interior or exterior of existing glass, with the option to leave them on permanently or remove them later, depending on the product. Many products have DIY options and simple installation procedures: applying a solution to a clean window and squeegeeing on the cut-to-order film. 

Types of Retrofit Window Coatings

Thermal Insulating Film – Adds an insulating layer to reduce heat transfer, offering modest energy savings while helping to improve comfort and reduce drafts. These films are instrumental in winter, as they help trap indoor heat, minimize drafts, and maintain more consistent interior temperatures. Conventional low-emissivity window films can improve a window’s insulating performance by up to 44 percent. In addition to thermal efficiency, these films can reduce condensation on windows by up to 50 percent, helping prevent mould growth and moisture-related damage. The average cost of a DIY installation is $1.28/sq.ft, with products found at local building supply stores.

Spectrally Selective Film – Blocks infrared heat and UV light while allowing the transmission of natural visible light. These are ideal for hot climates where solar gain is a significant issue. These films are highly effective at managing solar heat, capable of rejecting up to 97 percent of the sun’s infrared light. They also block over 99 percent of harmful UV rays, which helps protect furniture, flooring, artwork and other materials from fading and deterioration. While their upfront cost is typically higher – at $3.20/ sq.ft. for the DIYer – than that of standard window films, the long-term energy savings (especially in cooling-dominant regions) can make them a worthwhile investment.

Nanomembranes – Also known as low-E membranes, nanomembranes are applied to glass to reduce heat transfer by reflecting infrared radiation while allowing visible light to pass through. One example of this is Ecolosynergy. It was designed for large-scale commercial, institutional and residential buildings and blocks up to 95 percent of ultraviolet and 67–95 percent of infrared rays. The result is a reduction in heating and cooling energy use. According to Terry Nother of Ecolosynergy, “Savings in the 30–40 percent range are common, with added benefits like reduced equipment wear, UV protection, and noise abatement.”

Energy Savings and ROI

Looking at the ROI and payback of one of these three types of window coatings, Ecolosynergy’s nanomembrane has an average cost of $15/sq.ft., installed in Canada. Using the same size and number of windows as the example above, the price per window is $180. At 10 windows, the whole energy retrofit comes to $1800. According to energyhub.org, the average annual household electricity bill in Canada is $1750. Similarly, the average gas bill is $1310 for a total yearly expenditure of $3060. Now, this total includes more than heating and cooling costs. To break that out, we look to data from Natural Resources Canada, which indicates that the average space heating and cooling costs account for about 64% of residential energy use in Canada. Therefore, the average annual spend on energy is approximately $1,950. With an efficiency rating of 30 percent, the average annual cost savings of applying an Ecolosynergy low-E membrane comes out to about $585.

Based on the above calculation, the payback for a project of this size is approximately three years, a notable difference from that of low-E integrated replacement windows. Even if a retrofit project cost stretches the ROI to four or five years, it’s still far more appealing because it presents tangible returns to the homeowner.

Incentives

It’s also important to note that neither of the ROI examples include government or utility provider incentives. Both windows and low-E coatings qualify for specific incentives. To give you an idea of how much you can save, Nother installed Ecolosynergy as a DIY project in his home at a cost of $1,009 and he received a $1,000 rebate from the London Environmental Network. Similarly, Save on Energy and other incentive programs offer rebates that can reduce project costs and increase ROI. 

You can search for the right incentives applicable to you with our Incentive Finder.

Which Option is Better?

While new low-E films can dramatically improve a building’s energy performance, comfort and operational cost at a lower price than window replacements, the best option ultimately comes down to the age of your windows. If your windows are old, nearing the end of their lifespan, or showing signs of a needed replacement (like fogging, drafts and warped frames), investing in new low-E windows is the more practical decision, both economically and environmentally. Though the upfront cost is higher (around $850 per window compared to a standard glass window at $650), the upgrade improves durability, long-term performance and whole-building efficiency, with a payback period of roughly 10 years.

The decision to go for low-E window film depends a lot on the age of the windows. For aging windows it would be wasteful, as you will discard the film when the window needs replacing within a few years, creating unnecessary waste. Therefore, installing new low-E windows will make the most economic and environmental sense in that situation.

However, if your windows are under 15 years old and still in good condition, applying a low-E film or membrane can offer immediate energy savings at a fraction of the cost. Products like Ecolosynergy’s low-E membrane can reduce heating and cooling energy use by 30–40 percent, with a payback period of 2–4 years, especially when paired with rebates and incentives.

Ultimately, the smartest investment is the one that aligns with your building’s lifecycle. Full window replacements with integrated low-E coatings or retrofit low-E films provide a future-ready solution. Either way, low-E technology remains one of the most impactful upgrades you can make for sustainability, comfort and cost savings.

Read more on this topic in Triple-Pane Windows in Canada – Are They Worth It?