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Which Windows Are Most Energy Efficient?

11 May 2023


At Dempsey Dyer, we supply and install a variety of windows for your customers’ property, so it is important to understand which windows are best for energy efficiency, as they will be able to stay warm. In this article, we will go through a list of windows to look at which one is right for you. Read on to find out more.

Double Hung Windows

Double hung windows are an extremely common type of window and are generally the most energy efficient. They make it easy to control ventilation and light in different rooms. These windows have two sashes that slide up and down independently of each other, providing a great way to control the airflow in any room. The sashes are typically made of a sturdy material such as vinyl or fiberglass. They feature a tight seal that helps keep drafts out. It’s important to make sure the side of the window that doesn’t open is properly sealed to maximize the window’s energy efficiency.

Casement Windows

 Casement windows are another energy efficient option, offering excellent ventilation and light control. This type of window hinged on one side, and swings open from the side to provide an unobstructed opening. The tight seal around the window frame also helps to keep out drafts. Casement windows come in a variety of styles, including single- and double-hung, awning, and hopper. For maximum efficiency, choose a style with low U Values, which measure how much heat is lost through the window.

Sliding  Sash Windows

Sliding sash windows are just as energy efficient as double hung and casement windows. These offer excellent insulation, as the tight seal between the window frame and the window keeps drafts out. Sliding sash  windows feature two sashes that slide side to side, allowing you to control the amount of light and air entering a room.

Fixed Windows

Finally, fixed windows are an excellent choice for providing natural light and ventilation without compromising energy efficiency.  These windows come with advanced double glazing, so let your customer know that they will receive high levels of energy efficiency when they are properly installed. This way, their energy bills will be saved over time.

Make sure you hire a qualified installer to secure your windows correctly to ensure they remain energy efficient. With the right windows and proper installation, you’ll enjoy significant savings in energy bills and improved home comfort, all while reducing your environmental impact.

Double and Triple Glazed Windows

One of the best ways to improve a window’s energy efficiency is to upgrade to double- or triple-glazed windows. These windows use multiple layers of sealed glass panes to trap heat and cold air inside the home, reducing the amount of energy needed to keep the space warm. While double- and triple-pane windows are expensive compared to single glazed windows, they save money on energy bills in the long term.

Tilt & Turn Windows 

Tilt and Turn windows come in a wide selection of energy efficient glazing patterns. This will help give your customer plenty of customisation options that will ensure you have low thermal efficiency values. As a result, your customer will get plenty of privacy and customisation options.

Fiberglass Windows

Fiberglass windows are also energy efficient due to their ability to absorb and reflect heat from the sun. The material also provides superior insulation, helping to keep your home cooler in the summer and warmer in the winter, reducing your need for heating and cooling. While more expensive than other window types, fibreglass windows can pay for themselves over time through energy savings.

Storm Windows

Storm windows are an additional layer of windows that are installed over existing windows. These windows are designed to protect against wind, rain, and debris while also providing additional thermal resistance. Installing storm windows can significantly reduce heat loss during the winter and can also reduce heat gain during the summer.


We hope that this article has helped you understand which windows are the most energy efficient. Ultimately, the choice depends on the climate and specific needs of your home.

Double- and triple-glazed windows, low-E windows, fibreglass windows, and storm windows are all great options for improving your home’s energy efficiency. Investing in higher quality windows now helps you save money on your energy bills in the long run and reduce your home’s environmental impact.

If you want to find out more, our friendly team is on hand to assist you. Fill out our online contact form or call us on  01977649641. We look forward to working with you soon.


Installers and other businesses can only work effectively if they have a reliable trade supply service – offering the highest performing products. Luckily, here at Dempsey Dyer we only supply the latest options from market leaders. This guarantees quality, performance and durability – regardless of the product choice.


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