Window Film vs Double Glazing: Which Insulates Better?
Window film vs double glazing is a common comparison for anyone trying to make a home warmer in winter and cooler in summer. Both improve your windows, but they’re good at different things, and they cost very different amounts.
The short version: double glazing insulates better in winter, window film blocks more summer heat, and window film costs far less. And if you want the best result possible, the two work best together.
This guide uses Solar Gard’s published data to compare them honestly.
How heat moves through a window
Heat gets through windows in two main ways:
- Conduction: heat moving through the glass because one side is warmer than the other. This is how warmth escapes on a cold winter night. It’s measured by the U-value (lower is better).
- Solar gain: the sun’s energy shining straight through the glass. This is what makes rooms hot on summer afternoons. It’s measured by SHGC (lower is better) or TSER (higher is better).
Double glazing and window film tackle these differently.
Winter insulation: double glazing wins
Double glazing traps a layer of air or gas between two panes, which slows conduction. Here are winter U-values from Solar Gard’s Solar Control Film Selector Guide:
| Glass | Winter U-value (W/m²°C) |
|---|---|
| Single 6mm clear glass with standard film | about 5.6 |
| Single 6mm clear glass with Ecolux 70 Low-E film | 3.42 |
| Double glazing (3mm + 3mm) with standard film | about 2.7 |
| Double glazing (3mm + 3mm) with Ecolux 70 Low-E film | 1.93 |
What this shows:
- A Low-E window insulation film like Ecolux cuts heat loss through single glass by around 40% (5.6 down to 3.42).
- Double glazing does better again (around 2.7).
- Double glazing with Low-E film is the best of all (1.93).
So, for winter insulation, double glazing beats window film on single glass. But film still makes a big improvement, at a much lower cost.
Summer heat: window film wins
This is where many people are surprised. Clear double glazing is good at slowing conduction, but it does relatively little to stop direct sunshine. A west-facing double glazed sliding door still lets most of the sun’s heat in.
Solar control window film is designed specifically to stop that solar heat. Official Solar Gard figures on 6mm clear glass:
| Film | Heat rejected (TSER) |
|---|---|
| Ecolux 70 (Low-E) | 53% |
| Ceramic CX 35 | 58% |
| TrueVue 30 | 61% |
| TrueVue 15 | 77% |
In a Sydney summer, solar heat through glass is usually the bigger problem, and that’s where window film does the heavy lifting. See does window tint really reduce heat in a house?
Side-by-side comparison
| Window film | Double glazing | |
|---|---|---|
| Winter insulation | Good with Low-E film | Better |
| Summer solar heat | Much better | Limited (clear units) |
| Glare reduction | Yes | No (clear units) |
| UV protection | >99% blocked | Partial |
| Daytime privacy | Yes (reflective films) | No |
| Noise reduction | Minimal | Yes, especially with laminated glass |
| Cost | A fraction of the price | High: new glass and often new frames |
| Disruption | A few hours | Window replacement |
| Strata approval | Often needed for reflective films | Usually needed |
When to choose window film
Window film is usually the better choice if:
- Summer heat is your main problem
- You want to fix glare, UV and fading as well
- Your budget doesn’t stretch to new windows
- You’re renting or in a strata building where replacing glass isn’t practical
- You want results in one day without replacing windows
For winter comfort, choose a Low-E film like Ecolux. See our Low-E window film page.
When to choose double glazing
Double glazing is the better choice if:
- Winter heat loss is your main concern
- Noise is a big issue (main roads, flight paths)
- You’re renovating or building and replacing windows anyway
- You want the best possible insulation and budget isn’t the main factor
The best of both: film on double glazing
If you already have double glazing, or you’re installing it, adding window film is the way to get the best overall result. Double glazing handles conduction, and the film adds solar heat rejection, glare control and UV protection. Ecolux on double glazing brings the winter U-value down to 1.93, the best figure in Solar Gard’s guide.
Film on double glazing must be checked for compatibility with your glass, especially Low-E units. See can you tint double glazed windows?
What about the cost?
Double glazing usually means new glass and often new frames, which costs many times more than window film. Professional window film in Sydney typically costs $100 to $400 per square metre installed, depending on the film and the job. See how much window tinting costs in Sydney.
A common Sydney scenario
Here’s how window film vs double glazing plays out in a typical example: a family home with a large west-facing living room and single glazed aluminium sliding doors. In summer the room overheats every afternoon. In winter it feels cold near the glass.
- Replacing the doors with double glazing would improve winter comfort and noise, but it’s expensive, and the room would still get hot in summer unless the glazing includes solar control.
- A solar control film would cut the summer heat dramatically at a fraction of the price, but do less for winter.
- A Low-E film like Ecolux sits in between: it rejects 53% of solar energy in summer and brings the winter U-value of single glass down from about 5.6 to 3.42.
For many homes like this, Low-E film is the best value. If the family later upgrades to double glazing, a compatible film can go on the new glass too.
Noise: where double glazing clearly wins
In the window film vs double glazing comparison, noise is the clearest win for glass. If noise is your main problem, for example a busy road, a train line or a flight path, window film won’t help much. Film is far too thin to make a meaningful difference to sound. Double glazing, especially with laminated glass and a wider gap, is the right solution for noise.
Many people choose double glazing for noise and then find the rooms still overheat in summer. Adding a compatible solar control or Low-E film to the new glass solves the heat problem without affecting the noise benefit.
The bottom line
Window film vs double glazing isn’t really a contest. They do different jobs:
- Double glazing is better for winter insulation and noise.
- Window film is better for summer heat, glare and UV, and costs much less.
- Low-E window insulation film narrows the winter gap on single glass.
- Film plus double glazing gives the best insulation of all.
As a Solar Gard Authorised Dealer, we can recommend the right film for single or double glazed windows. Explore our Low-E window film and heat reduction window film pages, try our energy savings calculator, or send your glass sizes through the free quote form.
