What Homeowners Need to Know About 1.2 U-Value Sash Windows
by Northern Life
Homeowners today are looking for a perfect combination of style and efficiency in their home improvements. U-values are the most commonly used measure of thermal performance, so they’re a key number to look out for in the search for efficient windows.
What Is a U-Value, and Why Does It Matter?
U-values are measured in watts per square metre per degree Kelvin (W/m²K). In simple terms, how much heat passes through one square metre of a material – in this case, sash windows.
A lower U-value means better insulation. With less heat escaping through your windows, your home stays warmer and more energy efficient.
A higher U-value, on the other hand, means poorer insulation. As more heat is lost, your heating system must work harder to keep your home warm, resulting in higher energy costs.
Basic double-glazed or even single-glazed windows in old homes will have very high U-values compared to modern double-glazed windows with high-quality glazing and energy efficiency upgrades. If you’re living in a traditional property, consider upgrading to windows with lower U-values!

How a 1.2 U-Value Benefits Your Home
1.2 is an impressively low U-value, which means your windows are far better at keeping heat inside compared to older or standard options. Improved insulation and fewer draughts through your windows reduce wasted heat and keep your indoor temperatures stable.
With energy efficiency becoming increasingly important, they not only meet today’s standards but are designed to stay ahead of tightening regulations and rising expectations around sustainability.
Style Meets Efficiency

An impressive 1.2 U-value is achieved by leading manufacturers like Quickslide through advanced design and manufacturing methods, without diminishing the heritage appeal sash windows provide. Sash windows retain their traditional charm with slim sightlines and period details, combined with cutting-edge performance.
If you’re on the lookout for uPVC sash windows with an energy efficiency upgrade, Quickslide offers a range of finishes, hardware, and traditional features to really make the most of sash windows and their heritage appeal.
Why Choose a Trusted Manufacturer
It’s vital to do your research on any manufacturer you consider for your home improvements. Companies like Quickslide have a long list of accreditations demonstrating their commitment to quality and compliance backed by regular audits and recognised certifications.
To achieve an impressive 1.2 U-value on their sash windows, Quickslide made several key upgrades.
- Some of the steel reinforcement in the sashes is replaced with plastic, which insulates better and reduces heat transfer.
- Extra insulating materials get added into parts of the frame and cill to help minimise heat loss.
- The glass coating is upgraded to reflect more heat into the room, boosting overall energy efficiency.
What to Ask Before Buying 1.2 U-Value Windows

As with any purchase, it’s essential to understand what you’re getting when buying 1.2 U-value windows. Most of the time, it’s a matter of asking the right questions.
- Is the 1.2 rating for the whole window? Some companies only quote the glass, not the full frame.
- What type of glass is used? For example, Low E glass or gas-filled units that keep more heat in.
- Are the frames well insulated? The material and design of the frame make a big difference.
- Does it meet Building Regulations? Make sure the windows meet the required standards.
- What warranty comes with the windows? Check for guarantees on both the glass and the frames.
Investing in 1.2 U-value sash windows means you don’t have to choose between timeless style and modern performance. By combining traditional design with advanced insulation, you’ll enjoy a home that looks the part while keeping energy bills lower and comfort levels higher. With trusted manufacturers, you can be confident that your windows not only meet today’s expectations but are built to stand the test of time, adding long-term value to your property.