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Are Sliding Patio Doors Energy Efficient?


With energy bills the highest they’ve been in decades, having an energy-efficient property is more important than ever. The less energy you need to use, the cheaper your bills - and the less you need to rely on fossil fuels.

A building’s efficiency depends on a lot of things, including its design, insulation, appliances, and heating and hot water systems.

Something that’s often overlooked, however, is the efficiency of your doors and windows. Believe it or not, an inefficient door can cause the overall energy efficiency of a property to drop drastically. So, just how energy efficient are sliding doors, really?

Key Factors Affecting the Energy Efficiency of Sliding Doors

A door’s ability to conduct heat is measured using the U-value. The lower the U-value, the better the door is at stopping heat from passing through it.

Many sliding doors have glass as their primary material. Glass isn’t as good an insulator as timber or uPVC, which is why sliding doors traditionally have a higher U-value than other types of door.

However, developments in technology are changing this. Depending on how it is constructed and installed, a high-quality, modern sliding door can have a very low U-value. The factors with the biggest impact are:

Materials and Frame

When choosing a siding door, opt for one with a multi-glazed glass pane, as these will be much better at insulation. You should also consider what the frame is made of - aluminium is one of the best materials, as it is both durable and a good insulator.

Alimax’s MAXiSlide sliding doors are B-rated and feature a thermal break (internal insulation) to slow the spread of cold air from outside the property. They combine high-performance glass with a quality aluminium frame, ensuring excellent insulation for your home.

In addition, they are exceptionally strong against the elements, with air permeability of 600PA, wind load of 2400PA, and water tightness of 300PA.


If your door isn’t installed correctly, there could be gaps in its fixtures or frames. These will let in draughts and allow warm air to escape, reducing the thermal efficiency of your home.

When installing a sliding patio door, make sure it fits perfectly into its assigned space and that all gaps are completely sealed.


Always opt for a trustworthy manufacturer. Unlike cheaper, less experienced manufacturers, a reputable manufacturer will construct your door using high-quality materials and up-to-date practices, ensuring it is as energy efficient as possible.

At Alimax, we have decades of experience creating thermally efficient windows of exceptional quality in our state-of-the-art Hampshire factory. Our specialists are fully trained and use only the best equipment and premium materials to craft beautiful, bespoke aluminium patio doors.

If you’re looking to install a stunning sliding door to your home without compromising on energy efficiency, you've come to the right place. Get a quote by phoning us on 01425 205465 or by filling out our online form!