Did you know inefficient windows can account for nearly half of your home’s heat loss in winter? Upgrading can break that cycle and save you money in the long term.

Windows are among the most significant weak points in a house when it comes to energy efficiency. Up to 40% of a home’s heat can be lost through windows, especially through outdated single-glazed units. That’s why replacing old or underperforming windows is a smart move, not only for your comfort but also for lowering power bills and reducing your carbon footprint.

Energy-efficient windows are engineered to provide excellent thermal insulation. They help regulate indoor temperature, preventing heat from escaping in winter and blocking excessive heat in summer. This reduces the demand on your heating or cooling systems, cutting both energy consumption and costs.

But what exactly makes windows energy efficient? And why are they so critical to achieving a more comfortable and sustainable home?

How to Tell if a Window is Energy Efficient

The most important criterion to measure the energy efficiency of windows is the heat transfer coefficient, the so-called U-value, which is affected primarily by the total number of glazing layers, their dimension, the type of gas within their cavity, and the characteristic of coatings on the various glazing surfaces.

The U-Value

The U-value measures the heat permeability of building elements and indicates the heat flow through the window. It describes how much heat is allowed through the window from the inside to the outside. The value follows a simple rule: the lower the window’s U-value in W/(m²K), the higher the performance of the glass.  [i]

When determining the U-value of a window, several factors are taken into account. The U-value of a window Uw is calculated with the Ug (glazing), the frame material Uf (frame) and the coefficient of the edge bond Ψg.

When selecting new windows, it is worthwhile to choose the ones with the lowest possible U-value to reduce energy costs effectively.

For example, ECOWINDOWS standard double-glazed windows start with Ug-values as low as 1.10. This performance can be further enhanced depending on the window system. Our premium ECO WOODALU system with triple-glazing reaches an outstanding Ug-value as low as 0.5 – among the best in its class.

What Makes a Window Energy Efficient?

A window is a complex construct with several optimally fitted elements. The most important part here is the glazing, as the most energy can escape through the glass surface. Therefore, heat-insulating glazing is highly recommended.

Modern energy-efficient windows feature double- or triple-glazing with Argon gas filling and Low-E (low-emissivity) coatings that, generally speaking, prevent the heat in the interior from escaping to the outside. This performance is reflected in improved Ug-values compared to glass without Low-E coating.  [ii]

The frames and seals must also ensure optimal insulation and thus reduce energy loss through the window, for example, with multi-chamber profiles or draft-proof seals. Energy-efficient windows are well-sealed, which reduces the amount of air leakage. Unaddressed leakages can be a significant source of heat loss or gain. When old, outdated, or falsely installed windows create unwanted drafts, heating and cooling systems must work harder to keep a room comfortable.

The material quality of the window also plays a significant role. Quality European- and German-made windows offer an excellent thermal insulation effect, regardless of whether they are made of PVC, aluminium, wood or a combination of wood and aluminium. However, every material has unique properties and advantages, which should be matched with the individual requirements of your house.

To sum it up, the overall quality of the construction of a window is crucial: Only if all elements of the window are optimally coordinated with one another can the window fulfil its full potential and contribute to an environmentally friendly, healthy and cost-efficient building.

How Much Energy Can You Save?

The savings can be significant. Various studies indicate that replacing old windows with windows featuring thermal insulation glazing easily saves several hundred Dollars a year on small-family homes.  [iii]

Further, research shows that modernisation is particularly beneficial for windows with single glazing but also for windows with outdated, uncoated insulation glazing. Compared to modern insulation glazing, this is where the most significant savings can be achieved.

Outdated single-glazed windows have a very unfavourable heat transfer coefficient of 4.7 W/(m2K) in the best scenario – in most cases, this value is even worse. In a research study, this value was compared to modern windows with Low-E coating with a Uw-value of 0.95 W/(m2K) and a g-value of 62%. When replacing the single-glazed windows, around 491 kWh of energy or 49m³ of gas per window annually could be saved. [iv] (ECOWINDOWS offers windows with Uw-values starting at Uw 0,97 (ECO ALU 70) and going as low as Uw 0.58 (ECO WOODALU PH+)!)

More Advantages Than Just Energy Savings

Investing in energy-efficient windows is worthwhile in many ways. Even if energy efficiency and the resulting heating cost savings are the main reasons for replacing windows, new windows fulfil other essential functions, too.

Quality windows also offer improved burglary protection, reliably preventing the window from being forced open. They also increase living comfort as their weather tightness prevents drafts, which means that the room climate becomes warmer and much more pleasant. Modern manufacturing methods also enable excellent sound insulation for windows so that the interior is always wonderfully quiet – even when there is a lot of noise outside. Overall, windows are a long-term investment, and high-performing windows also increase the value of your property, which can be an advantage if you want to sell later on.

Is Your Home Ready for an Upgrade?

In summary, energy-efficient windows are vital in reducing energy consumption in homes by improving insulation, harnessing natural light and heat, and minimising air leakage. When properly installed and used in conjunction with other energy-efficient strategies, they can significantly contribute to a more sustainable and comfortable living environment.

Whether you are building a brand-new home or already own one and your current windows are several decades old and single-glazed with rusted or rotten and insufficiently thermally insulated frames. There is no doubt about investing in quality energy-efficient windows.

Just ask yourself the following:

• Do you want to reduce your energy consumption and power bills?
• Do you want to eliminate unpleasant drafts and improve your home’s comfort?
• Would you like to make necessary upgrades and increase your home’s value?

If you answered ‘yes’ to the above questions, it’s time to consider upgrading.

Why Choose ECOWINDOWS?

ECOWINDOWS can assist you in finding the right building solution for your home. We offer a wide variety of German and European windows, doors, shading solutions, and ventilation systems, all tailored to New Zealand’s climate: from the humid North to the frosty winters of Queenstown. Our products meet the highest Passive House standards and combine energy efficiency with stunning design.

If you would like to learn more about our product range or discuss your building project in more detail, please do not hesitate to contact us today.

[i] Unlike the desired high R-value, a lower U-value indicates better performance and insulation. The R-value is the reciprocal of the U value and vice versa (R = 1/U and U = 1/R).

[ii] There exist several types of coatings that should be matched to your home’s specific location, position and heating requirements. For example, there are “normal” Low-E coatings with a g-value between 0.5 and 0.7, which allow a large part of the solar radiation to pass through. This effect is good in winter because it reduces the heating load, but in summer, it isn’t good because overheating can occur. Once the heat is in the room, it can no longer escape through the glass due to the Low-E coating. On the other hand, there are also Low-E coatings with a reduced g-value (0.2 to 0.3), i.e. most solar radiation is rejected and does not reach the inside. This effect is good in summer because it reduces the risk of overheating. In winter, however, this also minimises the fact that the interior is heated by the sun. The heating load in winter is, therefore, higher. But don’t worry about the details – ECOWINDOWS can assist you in finding the best solution for your home!

[iii] Source: Link

[iv] ] Link