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Improve Your Home for Maximum Energy Efficiency

Improving your home with energy efficient windows and doors not only leads to substantial energy bill savings but also contributes to a reduced carbon footprint. Find out how to select your new windows and your future installer to maximise your benefits.

Energy Efficient Materials

Energy-efficient windows offer a diverse range of frame materials and styles, each affecting how well they keep heat in, allow sunlight, and prevent air leakage. Typically, these windows consist of two or three glass panes encased in frames made from materials like uPVC, aluminium, wood, or other innovative choices.


The design and material of your window frame significantly impact heat loss, and various options are available:

  • uPVC Frames: Designed predominantly for double glazed cost-effective options.
  • Wooden Frames: May have a lower environmental impact but demand regular upkeep, often seen in conservation areas.
  • Aluminum or Steel Frames: Boast durability and recyclability. With internal thermal brake like Idealcore, they can achieve passive house standard thermal insulation even with metals of high thermal conductivity.
  • Composite Frames: Combine an inner timber frame with an outer layer of aluminum, reducing the need for maintenance and ensuring weather resistance.


The glazing is the most crucial component of a window and significantly impacts its efficiency and performance. Not all glass is identical, and there are various types of glazing, each with specific purposes.

Low-E glass, coated with a thin layer of metal oxide, allows shortwave solar radiation to enter a room while reflecting longwave radiation back inside, effectively reflecting heat back into your home while still allowing in natural light.

Solar Control glass offers excellent thermal insulation and can minimize the amount of solar energy passing through the window, preventing overheating.

Combining Solar Control glass and Low-E glass in the same unit allows you to achieve a balance in climate control for both summer and winter.

Idealcombi uses Solar Control glass to reduce solar heat gain and provide superior thermal insulation. When combined with Low-E glass, it effectively reflects heat back into the room. This makes it an excellent choice for those seeking to lower their energy bills and reduce their carbon footprint.

Glass Spacing

The size of the gap between panes is a crucial factor that influences performance and acoustics. While an optimum thickness of 16mm is often recommended, smaller gaps may be more suitable in certain scenarios. Additionally, filling these gaps with inert gases like argon, xenon, or krypton can further enhance performance. Idealcombi windows incorporate high-performing pane spacers with minimal or no metal, commonly referred to as ‘warm edge’ spacers. These are located around the inside edges to keep the panes of glass apart.

Benefits of Energy-Efficient Windows and Doors

Reduced heat loss
Lower heating bills
Less condensation and drafts
Reduced carbon footprint
Enhanced property value

Costs and Savings

The cost of windows and doors varies depending on materials and style. Generally, PVC windows tend to be more budget-friendly, while hardwood frames are considered a premium choice. A good sweet spot are composite windows as they are cost-effective compared to hardwood thanks to softer pine wood and improved durability of external aluminium.

Finding a Trusted Installer

An installer is responsible for more than just fitting a window; they are also responsible for measuring and supplying the following:

  • Flashing: This is crucial to prevent water infiltration around the window frame and to prevent leaks.
  • Weatherstripping: It helps seal gaps and prevent drafts, enhancing energy efficiency.
  • Sealant: Sealant is applied to seal gaps and joints, ensuring the window is airtight and waterproof.
  • Insulating Materials: Materials like foam or fiberglass are used to fill gaps around the window frame, improving energy efficiency.
  • Decorative Trim and Casing: These elements are installed around the window frame to provide a finished and aesthetically pleasing appearance.

Selecting a competent installer who is familiar with the products allows you to have peace of mind that everything will be taken care of and included in the price.

Choosing the Ideal Energy-Efficient Window

The energy performance of a window depends on a multitude of factors, making it challenging to select one based solely on its construction. Fortunately, bespoke windows can be manufactured to any requirements. Things you should consider when selecting windows are U-Values, G-Values, and frame type.

U-Value: Measuring Heat Loss

The U-value of a window measures the extent of heat loss due to thermal transfer. It measures the movement of heat from the warmer side to the colder side of the window, influenced by factors like the type of glass, gas fillings, and spacer bars between the panes.

The U-value is rated on a scale from 0.01 W/m²K (representing ultra-low heat loss) to 4.6 W/m²K (indicating high heat loss in single glazing). The rule of thumb is simple: the lower the U-value, the better your home retains warmth. In practice, you can expect typical U-values such as 0.51 W/m²K* for double glazing and 0.39 W/m²K* for triple glazing in our windows. These low U-values can be further improved by using a combination of Low-E glass and a Solar Control coating like Suncool.

*U-Values indicated for windows in standard testing size 1230mm x 1480mm

G-Value: Understanding Solar Gain and Heat Transfer

The G-value of a window specifies the solar gain and heat transfer. It measures how much solar heat enters and how efficiently heat moves through window glass.

The G-value is quantified on a scale from 0.01 W/m²K (indicating minimal heat loss) to 4.6 W/m²K (representing high heat loss). The general rule is simple: the lower the G-value, the better your windows are at controlling heat and preventing overheating. In practical terms, you can expect typical G-values of 0.51 W/m²K* for double glazing and 0.39 W/m²K* for triple glazing in our windows. To enhance energy efficiency, we offer the option of combining Low-E glass with a Solar Control coating like Suncool.

*G-values indicated for windows in standard testing size 1230mm x 1480mm

All Idealcombi glass units use minimum Argon gas, with the option to use more advanced gases like xenon, or krypton(recommended for passive house projects). Furthermore, our slim-profile frames are equipped with Idealcore insulation to further decrease heat conductivity.


New windows tend to be more airtight, which can lead to increased condensation if your home lacks adequate ventilation. When looking for replacement windows, consider those that incorporate trickle vents within the frame, allowing for controlled ventilation. Concealed trickle vents provide all the benefits of standard trickle vents while maintaining a clean external appearance.

If you notice condensation building up around your windows, it may be indicative of a damp problem in your home. This issue can result from insufficient ventilation, low heating levels, insulation gaps, high moisture production, or problems with guttering and pointing. Condensation between the glass panes in your double glazing units likely indicates a broken seal, necessitating unit replacement. However, condensation on the outside of your windows is a positive sign of efficient insulation and should not lead to damp problems. It usually clears quickly and does not pose any issues.

Windows in Conservation Areas and Period Properties

If you reside in a conservation area, it’s essential to consider the architectural and historical significance of your surroundings. While window replacement is feasible, it should align with the character of the building and the area. Seek guidance from your local council’s conservation officer.

Listed Buildings: Listed buildings necessitate permission for window alterations. Often, secondary glazing serves as an approved method to insulate historic windows from within. Consult your local council to explore the available options.

In both cases, you can opt for aluminium windows that match the style of your current frames. This approach allows you to get the benefits of energy efficiency and still retain the old style.