Energy efficient windows_energy efficency

Which windows are most energy efficient? A simple guide to making the right choice.

Glass is an awful insulator! Like one of the worst! 

Energy efficiency is therefore really important when selecting which windows to use in your extension or new build project as they can make a huge impact on how much heat is retained in your property. 

The importance of reducing our carbon footprint is evident everywhere, and one of the most dramatic differences you can make is ensuring your property is properly insulated.

In this article, we give you a guide so that you can understand how to choose the best energy efficient option for your home.

Why is energy efficiency important when choosing your windows?

Choose a window that is poor for energy efficiency and you will soon find yourself spending more on your fuel bills to heat your home, as the heat quickly escapes out the window rather than being contained within your property.

Not only is this a waste of money, but it also has a negative impact on the environment.

Energy efficient windows will help to retain the heat and keep your property warm in the cooler seasons if used in combination with roof and wall insulation. In addition they will also keep your property cool on warmer days in summer. 

What is WER ?

WER stands for Window Energy Rating.  People often think that making your windows more heat efficient is as simple as having double glazing in place but this isn’t quite the case, (although it certainly is a starting point).

The aim is for WER to simplify the more complicated values for thermal efficiency, solar gain and air leakage into one basic rating for overall energy efficiency so that people can make a more educated decision.

Window manufacturers can show the energy efficiency of their products using an energy-rating scale from A++ to E issued from the British Fenestration Rating Council. A++ being the better performing window for energy efficiency. 

Which windows are most energy efficient? A simple guide to making the right choice.

The whole window (the frame and the glass) is assessed to allow for heat loss, draughts and solar gain, giving a rating that indicates the overall impact of fitting that window in your home. 

In October 2010 legislation was introduced that meant new windows needed to have a minimum window energy rating of band C in a conscious shift to look after the environment. 

What makes a window energy efficient?

The heat inside your home is always trying to equalise with the lower/higher temperature outside your home. In summer, conservatories are often stifling as the heat transmits into the room; however in winter, these rooms can be very cold as the outside temperature sucks the heat out.  Energy efficient windows attempt to reduce this impact so that heat transition is minimal. 

Energy efficient windows are typically double or triple glazed, meaning that there are two or three panes of glass fitted into a single frame unit.  The gaps in between are then filled with air to further prevent the heat from travelling through.  Air is a poor conductor, therefore the heat finds it more difficult to escape. In higher energy efficient windows these spaces are filled with argon or krypton gas, both of which are odorless, non-toxic and transparent in colour.  

The glass panes can also be coated to increase energy efficiency. The technology works in a way that it repels the sun’s rays away on the outside but also reflects the heat back into your home on the inside.

It’s important to note the larger the windows and the higher the quantity of windows within your home the more important it will be to ensure a more energy efficient provision is in place. 

Are certain window styles more energy efficient than others?

energy efficient windows

Fixed windows are generally deemed as the most energy efficient as there is no requirement for opening mechanisms, they can therefore create a snug seal against the outside environment.

Turn & tilt window

Casement windows alongside turn & tilt windows are realistically joint second. They both form a tight seal on all four sides and when closed, the handle triggers a mechanism that pulls the frame and window firmly together. 

Sash & case and sliding windows are less energy efficient due to the way they need to move against each other in order to open. However, the designs from window manufacturers have drastically improved over the decades and are a vast improvement on the original designs that you’ll find in older period properties.  Planning permission often restricts the property owner from using more modern materials when renovating, so it is important to explore any constraints that your property may need to adhere to. 

Related Content: Window Styles; a guide to the most popular

energy efficient windows

How much more do energy efficient windows cost?

Energy efficient windows that are A++ rated will come at a higher price to less efficient windows, however some of this cost can be displaced by the heating bills you will make savings on.

The cost of an energy efficient window will vary depending on your choice of frame material, window style, and size. Therefore when weighing up the best options, it is about identifying your priorities and striking a balance between them. For example, if you want the best energy efficiency, but are tight on budget you may choose to compromise on your aluminium frames and opt for UPVC which is the cheapest material choice in the UK. 

Prices start from around £250 ranging upto £750 for a fairly standard sized casement window; a gable end design could set you back upwards of £2,000 for a good energy efficient model. 

Window Grants

In July 2020, the UK Government announced a new home improvements grant scheme, called the Green Homes Grant Scheme. The new scheme allows homeowners and landlords to claim vouchers worth up to £10,000, to install energy saving measures in their homes, including for double glazing (windows and doors). For more information, click here to visit the Energy Saving Trust.

Related Content: Windows: What is the best window frame material?

Additional energy efficiency measures for your home 

In addition to selecting energy efficient windows you can further improve your homes insulation by combining it with additional measures such as : 

  • Hang thick curtains 
  • Insulate your roof & walls
  • Apply draft excluders to doorways
  • Minimise gaps around pipework
  • Upgrade your boiler if it is not operating effectively. 

Summary: Which windows are most energy efficient?

When considering how to spend your home improvement budget, energy efficiency is not a consideration to overlook. Costs may be higher upfront however you can reap the savings on your heating bills over time.

The British Fenestration Rating Council use WER to communicate how energy efficient a window is. The best performing windows are A++ working down to E, legislation in the UK now requires all new windows need to be of a minimum C rating, to help reduce our carbon footprint.

Fixed windows are the most energy efficient window style, however technology advancements mean that all options can now meet the required C rating.