Energy efficient windows - The right temperature for a better living

Energy efficient windows - The right temperature for a better living

Comfort is a feeling. From fighting the summer heat to keeping warm in the colder months, finding the right temperature in your home it’s an important step to make a comfortable place for your family to enjoy. Installing energy efficient windows will make a considerable difference in terms of comfort of your home and lead to energy bill savings in the process.


Save money on your energy bills

Energy efficient doors and windows can significantly reduce your energy bills, and VELFAC windows have established an unrivalled reputation for low energy performance.

When we talk about ‘energy efficiency’ we are talking about reducing - or even eliminating - energy waste in your house. In the average home, 20-25% of heat is generally lost through windows and doors.

Heatloss - thermal efficiency.jpg

Typically, heat loss around thermally deficient windows and doors can occur via:


  • Air leakage around the frame
  • Air leakage around opening sashes
  • Conduction through glazing panes
  • Conduction through the window frame



There are four aspects of a window that need to be considered as they contribute to its energy efficiency:


Frame material

Apart from the glass, the material used in the frame makes a difference in heat loss from the window. The thermal conductivity of the frame contributes to how much heat is transferred from a room to the outside. Wood has a low conductivity and it is the best material to improve thermal efficiency. Metals have the highest thermal conductivity therefore insulation can be an issue. 



The distance between the panes of glass makes a difference to thermal conduction and heat loss through the glazed area. A sealed unit filled with an inert gas such as Argon has a lower transmission and is more efficient. A unit with wider spaced panes of glass is also more efficient. The spacer bar used to separate the panes of glass also acts as a thermal bridge to conduct heat. Modern spacer bars known as ‘warm edge’ are made from a steel-reinforced polymer and reduce thermal conductivity.



The glazing is the most significant part of a window and makes a big difference in efficiency and performance. Glass is not all the same and there are several types of glazing. Low-e glass is generally the preferred option for maximum heat retention and efficiency. To improve insulation, triple glazing windows are the best solution. 



Often overlooked, installation quality is just as important as product quality. You can choose the best performing windows and doors, but if the installation is not carried out properly, you won’t be experiencing any of the benefits in terms of comfort or energy saving in your home.


Key factors to be considered when choosing energy efficient windows

U-values, your windows thermal efficiency indicator

When choosing new windows and doors, it might seem overwhelming to consider all of the components outlined above.


A simple way you might choose to compare products is by considering their U-values. 


In simple terms, the U-value measures the amount of heat allowed to escape through a window (heat loss). In both cold and warm climates good U-values are important measures for understanding the amount of energy that is needed to keep a comfortable inside temperature. When assessing a window’s ability to retain heat (insulation), the lower the U-value the better.

Solar Gain and Air Leakage

Solar Gain (G Value) – Homeowners want to use as much natural energy as possible from sunlight, rather than paying to heat the house. The G value measures how much heat from the sun’s rays passes through the window.


Air Leakage (L Value) – Air leakage is the technical term for draughts, so the L value measures how airtight windows are. If there is a weak point around the window, this will be spotted. You want to aim for an L value of 0 for the most energy efficient window.


Choosing new modern energy-efficient windows, you’ll take advantage of sunlight and avoid excessive heat loss through the pane. This could save you up to 30 percent on your heating bills compared to older windows.

External factors

Beside U-Values and good installation there are some external factors that need to be considered when planning a low energy home:


  • The windows’ orientation in relation to the sun
  • Sun screening and shading
  • The glass ratio
  • The number of windows and total window area
  • Air tightness

Discuss your project with a VELFAC distributor

Tell us about your project by filling a form and we will get you in touch with one of the distributors in your area. VELFAC distributors offer a wide range of services to help you every step on the journey to your new windows and doors.


Discover VELFAC windows and doors

VELFAC Energy efficient windows

The VELFAC slim frame maximises solar gain and natural light – reducing dependency on artificial heating or lighting – and helps reduce U-values further, as glazing is usually more energy efficient than the frame.

VELFAC glazing use argon gas in between glass panes and can achieve a U-value as low as 0.8W/m2K .



Frequently asked Questions


When you are considering new energy efficient windows or patio doors, there can be many relevant questions that you want answered. We have gathered some of the frequently asked questions right here.

What should I look out for when choosing energy efficient windows?

The components that make up a window all contribute to its functionality and insulating properties. Frame materials, glazing features and installation all play an important part in the performance of energy efficient windows and doors.


Frame material – Consider the thermal conductivity of the frame material when choosing your windows. Comparing timber and aluminium frames, for example - timber is much more effective as an insulator than aluminium, and is similarly superior in this department to uPVC. Windows that combine internal wood and external aluminium , like VELFAC composite windows , combine the best of two material to achieve high energy efficient windows.


Glazing – Single glazed windows no longer meet current building regulations on thermal performance. Double glazing is today the most popular forms of glazing. The two glass panes are inserted in parallel separated by a cavity filled with gas which has an insulating effect. For triple glazed windows, there will be two cavities, and this provides better insulation.


Installation - Efficient windows and doors can be compromised, and their benefits wasted, if not installed correctly. Various measures can be taken throughout the installation to minimise air loss around the windows and doors. Examples include using airtight expanding foams between the units and the structural opening. We always recommend not installing energy efficient windows yourself, instead choosing a reputable and experienced professional for a complete peace of mind.

Double or triple glazing units?

The choice between double glazing units or triple glazing units depends on a number of factors such as your home’s level of insulation, the orientation of each room to the sun and your budget. Recent changes in Building Regulation have set challenging new performance standard for windows and doors. For example, the current maximum U-value for a window is 1.2W/m2K, but this will drop to 0.8W/m2K in 2025. This lower U-value target can be easily met by triple glazing but not by double glazing. Anyway, we usually suggest a mix of the two, in order to achieve the best thermal efficiency rating while keeping the cost low. You can find more info right here.

Can you achieve superb comfort levels in your home without compromising on aesthetic?

The answer is yes.


VELFAC currently offer one of the most energy efficient window system on the market and also feature a slim 54mm frame, which lets more light in and can give your home a beautiful, contemporary look. In addition, both double and triple glazing windows frame look the same, giving a beautiful uniform look to your home.


Browse our Gallery page for more inspiration.

Discover VELFAC. Come and see our range of windows and doors

Windows and doors are a big investment, so it’s important that you see and experience their ‘ touch and feel’ before you take your decision.

Visit a local showroom

Many of our distributors have local showrooms where you can see our range of windows & doors and discover the options available to you. Fill our form adding details about your project, and we will get you in touch with one of the distributors in your area.