What makes a window Passivhaus approved?

The aim of the Passivhaus (Passive House) accreditation is to help ensure that both new and existing buildings become net-zero carbon ready.

To achieve Passive House accreditation, windows require a maximum U-value of 0.80W/m2K (0.85W/m2K installed) for the whole window. These stringent requirements are to ensure that the buildings have great insulation and are highly thermally efficient, which helps less heat energy escape through the windows, leading them to be more sustainable.

This article will provide information which should be considered in order to achieve this classification.

What is a window profile?

A window profile is the frame of a window and is comprised of several chambers. By increasing the number of chambers, the window provides better thermal insulation, subsequently becoming more efficient. The profile of a window is a vital design component as it also helps to stabilise the frame.

When choosing a window to purchase, it is best to find a frame with a high number of chambers in order to achieve the Passive House standard.

What is the most efficient type of window glass?

The type of glass used in your windows can make a huge difference to their overall efficiency. Low-E glass is designed to deflect heat in summer and trap it in winter, and to block UV rays whilst also allowing light to reach your rooms.

Although low-E glass is more expensive than more basic types, it will save money on energy bills and installing it can also increase the overall property value.

When choosing glass, it is also worth considering how many layers of glazing to install. Double glazing can be just as efficient as triple glazing depending on the overall unit thickness, however, triple glazing over 36mm thick allows for optimal thermal performance.

To further improve insulation, gases such as argon can be inserted between the layers of glazing.

What is a warm edge spacer bar?

Spacer bars are a component placed in between the window glazing and are essential to insulating windows. They can be manufactured using a variety of different materials, but traditionally used aluminium. The drawback of this metal is that it is a conductor, so is thermally inefficient.

To better insulate the windows and help them to reach Passive House standards, warm edge spacer bar technology is used, such as Edgetech’s Super Spacer®. Made from a non-conductive foam, this spacer will better insulate the windows, whilst providing more flexibility which improves the windows’ performance against changing weather conditions and other external pressures. Edgetech’s Super Spacer® has been presented with an official Passive House component seal, and around a third of all UK glass units are now made with Edgetech warm-edge technology.

Is there an alternative to silicone window sealing during installation?

Due to its affordability and ease of application, silicone has been the market leading window sealant for many years. Despite this, there are various drawbacks surrounding its use, particularly where efficiency is a deciding factor. As an insulator, silicone typically offers U-values of 2.6 or higher, when Passive House requires a value of 0.7. It also hardens over time, so is less durable in the long term.

To maximise insulation and avoid serious future complications, consider using TruFit. As a compressed foam insulating seal, this form of insulation is even easier and more accurate to use. Installers only need to remove the backing paper and apply, before the tape steadily expands to seal all gaps between the frame and wall. TruFit’s flexible design also ensures it will not stiffen over time, which allows movement and provides longevity, in addition to increasing thermal efficiency.

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