Window Renovation in Focus - Tips from the Expert

Today, we would like to give you an insight into the topic of window renovation. To do this, we talked to Hendrik Schimmele, a window expert working in technical sales at SIGA. He shared valuable information and tips with us regarding the renovation of old windows.

Stefanie Schaller
in products , airtightness , windtightness
4 minutes reading time

Why is the renovation of old windows so important?

Not only due to the energy crisis, but many windows in Europe and worldwide will be renovated in the coming years. Many windows from the 1960s and 70s were not adequately sealed and often did not have double-glazed panes. Thanks to double- or triple-glazed windows, a building's tightness increases, saving energy. Today, it's crucial to minimize energy loss and prevent mould formation. Proper renovation is key, and as an installer, you can make a significant contribution here.

What should be considered during window renovation?

Proper installation during window renovation is crucial, whether it's wooden windows, wood-aluminum, plastic, or pure aluminum windows. Just like in new construction, generally accepted rules and techniques must be followed during renovation. In the UK the Part L regulation applies. According to the Part L guideline, the following techniques are approved for window renovations:

Windows and doors: to ensure continuity of the air barrier, window and door units should connect to the primary air barrier and window and door frames should be taped to surrounding structural openings, using air sealing tape. Compressible seals or gun sealant may be used to supplement taping.”

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The general goal is to minimize energy loss and prevent mould formation.

How do I effectively seal a window against drafts?

Effective draft sealing is a crucial factor in window renovation. The degree of renovation plays a role here. Hendrik explains, "With a core renovation using a thermal insulation composite system, you can almost achieve the new construction standard. In this case, a joint sealing tape like Fentrim 20 can be used, which can later be completely plastered over." However, for a simple window replacement renovation, different materials are needed. Here, a liquid sealant is the best choice to ensure technical sealing. You seal the joint as follows:

1. Insulate the joint

2. Insert a backer-rod. This can be a PE or PU round cord. Important: Consider the width-depth ratio between the joint and cord.

3. Apply Meltell

Tip: You can use Meltell for wider joints up to 35mm. This can be very helpful, especially in renovations of older buildings.

What types of sealants are there, and what are their differences?

There are different sealants for window renovation, each with different properties. Hendrik explains that acrylic is a sealant specifically suitable for indoor use and can be painted over later. However, it's not particularly moisture-resistant and less flexible, making it an older sealing standard. Outdoors, silicones are commonly used, offering better resistance to driving rain and greater flexibility.

An interesting advancement is hybrid sealants, combining the best of acrylic and silicone. These can be used both indoors and outdoors, are paintable, and offer high flexibility. Hendrik recommends products like SIGA Meltell, which can even be used at temperatures down to -10 degrees Celsius and are ideal for joint widths up to 35 millimeters.

How do I calculate the right amount of sealant?

A common issue in window renovation is determining the exact amount of sealant needed. To provide certainty, SIGA has developed a joint calculator. With this tool, installers can easily enter the width, depth, and length of the joint. It also automatically calculates the amount of material needed in tubular bags or cartridges.


Renovating old windows is important during the energy crisis. Proper renovation can help minimize energy loss and prevent mould formation. Choosing the right sealant is crucial, and modern hybrid sealants like Meltell can offer an optimal solution. Thanks to SIGA's practical joint calculator, determining the exact amount of sealant is effortless.

We thank Hendrik for his tips and hope that this article assists you in your window renovation projects. For specific inquiries, feel free to contact your SIGA representative. Find your local SIGA Contact person | SIGA.

Best of luck with your renovation projects!

From Carpentry to Technical Sales: About Hendrik Schimmele

Before joining SIGA, Hendrik Schimmele earned his title as a master carpenter. During this time, he worked in both small and large industrial companies. Hendrik has been working in Technical Sales at SIGA for 10 years now and possesses comprehensive expertise in the field of window and facade construction. He shares his knowledge through specialized seminars and conferences across Germany with planners, architects, engineers, and experts.

Stefanie Schaller

HR Marketing and Employer Branding Manager on a mission to position SIGA as a great employer. Outside of work, she enjoys immersing herself in the world of books, passionately practices yoga, and is a proud mum.

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