When you’re looking at buying new windows for your home, you’ll often hear about uPVC, aluminium, sight lines, and frame profiles. Although it can start to sound technical very quickly, these details matter when it comes to how your home looks, feels, and how much light comes in. Let’s break it down.
What are uPVC and aluminium?
uPVC (unplasticised polyvinyl chloride) is a type of plastic used extensively in the window trade. It’s lightweight, durable, and low-maintenance. White uPVC are probably the windows you see most often in homes up and down the UK, and for good reason. They’re affordable, don’t rot or rust, and they do a solid job with insulation.
Aluminium windows, on the other hand, are made from metal and are often used in more modern or high-end projects. They’re strong, sleek, and can support bigger panes of glass because they don’t need to be as chunky as uPVC frames to stay rigid.
Frame Widths
Frame width (sometimes called profile) is exactly what it sounds like — how thick the window frame is around the glass.
- uPVC frames are generally thicker. That’s because plastic isn’t as naturally strong as aluminium, so it needs more bulk to support the same window.
- Aluminium frames are slimmer, thanks to the metal’s strength.
The thicker the frame, the less glass you have. And less glass = less natural light.
uPVC Frame
Thicker frame, less sightline.
Aluminium Frame
Thinner, stronger frames - more glass.
Sight Lines
The sight line is basically what your eye sees when you look through the window — including how much frame you’re looking at versus how much view you’re getting through the glass.
If you have slim sight lines, the window frame is less intrusive, and you get a cleaner, more open view. So, if you want maximum daylight, slim sight lines (aluminium) are better but more expensive than uPVC.
Frame Profiles
The profile is the shape and design of the window frame. Some are flat and modern, and some are more sculpted or decorative – often to suit traditional or older homes.
- uPVC has more options for decorative profiles. Think Georgian-style or classic curves.
- Aluminium tends to be a more modern design — sharp, clean lines with minimal fuss.
The Bottom Line: What Should You Go For?
It depends on what is most important to you:| What You Want | Go For… |
| Low cost and good insulation | uPVC |
| Sleek, modern look | Aluminium |
| Bigger panes of glass / more light | Aluminium |
| Traditional look, classic style | uPVC |
| Lower maintenance long-term | Both are solid |
One Last Thing
There’s no wrong answer when it comes to choosing your window frame — just different options for different homes and personal preference. But, when you get the right ones, they can make your home brighter, warmer, and better-looking.